[HN Gopher] Building the System/360 Mainframe Nearly Destroyed IBM
       ___________________________________________________________________
        
       Building the System/360 Mainframe Nearly Destroyed IBM
        
       Author : rbanffy
       Score  : 134 points
       Date   : 2025-04-08 07:30 UTC (15 hours ago)
        
 (HTM) web link (spectrum.ieee.org)
 (TXT) w3m dump (spectrum.ieee.org)
        
       | FpUser wrote:
       | This was some great read
        
         | ListeningPie wrote:
         | Your comment was reason enough for me to read it, 8/10
        
       | noworld wrote:
       | The successor IBM Mainframes are still alive... for the time
       | being.
       | 
       | https://www.redbooks.ibm.com/redbooks/pdfs/sg248329.pdf
        
         | froh wrote:
         | oh, they'll stay around for another while.
         | 
         | they also moved on three more CPU generations since that
         | redbook, to z17.
         | 
         | I think it's Linux on Z that makes it sexy and keeps it young,
         | in addition to a number of crazy features, like a hypervisor
         | that can share CPUs between tenants, and a hardware that
         | support live migration of running processes between sites (via
         | fibre optic interconnect) and the option to hot swap any parts
         | on a running machine.
         | 
         | It's doing a number of things in hardware and hypervisor that
         | need lots of brain power to emulate on commodity hardware.
         | 
         | _and_ it's designed for throughput, from grounds up.
         | 
         | Depending on your workload there may be very good economical
         | reasons to consider a mainframe instead of a number of rack-
         | frames.
        
           | rbanffy wrote:
           | > I think it's Linux on Z that makes it sexy and keeps it
           | young
           | 
           | They _feel_ fantastic when running Linux, but, if you don 't
           | need all the reliability features that come with the
           | platform, commodity hardware might be a better choice for the
           | kind of workload that has evolved on Linux.
           | 
           | > Depending on your workload there may be very good
           | economical reasons to consider a mainframe instead of a
           | number of rack-frames.
           | 
           | Absolutely - it makes a lot of the administrative toil
           | disappear. I know clusters are sexy, but getting the job done
           | is always better.
        
           | trollbridge wrote:
           | Other than IBM's absurdly high pricing, they're cheaper to
           | run in almost every way than x86 machines (including cloud).
           | I haven't done the math to compare with aarch64/ARM.
           | 
           | But most people don't want to deal with the hassle of dealing
           | with IBM.
        
           | MrBuddyCasino wrote:
           | I suspect the main reason isn't just strictly economical. If
           | you are Google or some such you can probably compensate by
           | building smart software around commodity hardware, but most
           | companies simply can't. Even if they have boatloads of money
           | (banking, insurance) and can hire expensive talent, they
           | simply can't successfully complete such an undertaking
           | because they don't have it in their DNA, and management isn't
           | incentivised to take on such a risky project.
           | 
           | In this case they will just use a mainframe, even it isn't
           | cheaper in the long run.
        
             | cmrdporcupine wrote:
             | Thing is Google does not use commodity hardware for their
             | DCs as far as I can tell. They got famous for that back in
             | the early 2000s but I think they abandoned that approach a
             | long time ago.
        
               | MrBuddyCasino wrote:
               | They may design their own hardware, but their approach to
               | scaling and fault tolerance is still the same: not a low
               | number of fast and very expensive enterprise grade
               | hardware that is unlikely to fail, but a huge fleet of
               | servers that scale horizontally and that can tolerate the
               | loss of a machine.
               | 
               | Which is the Mainframe vs commodity server dichotomy.
        
           | jasode wrote:
           | _> Depending on your workload there may be very good
           | economical reasons to consider a mainframe instead of a
           | number of rack-frames._
           | 
           | For legacy companies yes but it would be very hard for new YC
           | companies or existing non-mainframe companies to create a
           | spreadsheet showing how buying a new IBM Z mainframe would
           | cost less than the latest commodity x86 or ARM servers in the
           | cloud or on-premise.
           | 
           | The IBM pricing for mainframes makes sense for legacy
           | companies like banks and airlines with a million lines of old
           | COBOL code that want to keep it all running with the latest
           | chip technology. (The mainframes from a few years ago are
           | coming off the lease and they need to upgrade to whatever new
           | mainframe IBM is offering and sign another lease & service
           | contract.) So, IBM mainframe prices are very expensive -- but
           | legacy companies will pay it because migrating the code away
           | from mainframes _can be even more expensive_.
           | 
           | It's similar to expensive enterprise pricing of Oracle,
           | Embarcadero Delphi, Broadcom etc that takes advantage of
           | existing customers already locked into their products.
           | Virtually no new tech startup with a greenfield project is
           | going to pay Delphi $1599-per-seat for each of their
           | developers. Only existing customers stuck with their
           | investment in Delphi code are going to pay that.
           | (https://www.embarcadero.com/app-development-tools-
           | store/delp...)
           | 
           | But some companies do endure the costs of migration to get
           | out from IBM lock-in. There are lots of case studies of
           | companies shifting their workload from mainframes to
           | AWS/GCP/Azure. I can't think of a notable company that did
           | the reverse. Even a mainframe hardware vendor like Fujitsu
           | quit making mainframes and shifted to x86 running an
           | emulation of their mainframe os.
           | 
           | Yes, IBM mainframe can run other workloads besides COBOL like
           | Java and C/C++ but no company that's not already using
           | mainframes would buy & deploy to IBM's Z hardware for that
           | purpose.
        
             | Spooky23 wrote:
             | It's a risk issue. 5 year high risk projects aren't
             | appealing to CIOs with an average tenure around 18-36
             | months. Even if it works, why should the next asshole get
             | the credit?
        
               | KerrAvon wrote:
               | I think the point is that IBM's market is shrinking, and
               | they can't acquire new customers. They will eventually
               | need to stop making mainframes because there will be a
               | crossover between the cost for new mainframes for
               | remaining customers vs transition to commodity hardware
               | cost.
        
             | winrid wrote:
             | Building a fast reliable fault tolerant system is easier on
             | mainframes than the cloud you're familiar with.
             | 
             | Imagine having transactions ACROSS services. Do you know
             | how much bullshit and over engineering that gets rid of? A
             | lot.
        
             | twoodfin wrote:
             | _Virtually no new tech startup with a greenfield project is
             | going to pay Delphi $1599-per-seat for each of their
             | developers. Only existing customers stuck with their
             | investment in Delphi code are going to pay that._
             | 
             | I agree with this, and all your other reasons why
             | mainframes will remain legacy platforms.
             | 
             | But man, how crazy is it that an industry that is 100%
             | productivity driven and (until AI data centers, at least)
             | labor-cost-constrained would snub its nose at paying a
             | fraction of a percent of those developers' salaries to put
             | good tools in their hands.
        
             | froh wrote:
             | in a nutshell a mainframe is a cloud in a box for high
             | throughput workloads which need crypto and tpu
             | accelerators.
             | 
             | mainframe pricing usually is not by pound of iron but per
             | cpu cycle. unless you say nah I'm buying the thing, not
             | just cycles. soyou have a choice of cloud pricing or
             | hardware pricing.
             | 
             | for significant pure Linux workloads that need an own on
             | premise cloud the TCO pricing is surprisingly competitive
             | with any home grown solution.
             | 
             | even if you don't _need_ an own on premise cloud, AWS and
             | similar donate come for free and there may be a break even
             | there, too.
             | 
             | that said, legacy host software, Delphi, cics, Oracle,
             | DB/2, cobol etc, you named it, yes that's a different
             | story, with all the extra software licensing.
             | 
             | but a pure Linux mainframe is surprisingly competitive not
             | just in compute and throughput but also in pricing.
             | 
             | plus you get quite some high availability in silicon. think
             | ECC on the ALU, hot stand by spare CPU, multipath
             | everything, if your business depends on uptime your system
             | architecture becomes much simpler on highly dependable
             | hardware.
             | 
             | so that spreadsheet compares own people and software
             | construction vs IBM tax in some columns.
             | 
             | lol I start sounding like an IBM sales person
             | https://www.ibm.com/products/integrated-facility-for-linux
             | 
             | I just did Linux on Z for a while and I loved it, so please
             | bear my enthusiasm :-D
        
               | jasode wrote:
               | _> but a pure Linux mainframe is surprisingly competitive
               | not just in compute and throughput but also in pricing._
               | 
               | It's not competitive when you consider what long-time IBM
               | mainframe customers actually do. E.g. SABRE airline and
               | travel reservation system was one of the first IBM
               | mainframe customers in 1960 with the IBM 7090 and then
               | upgraded to System 360 and then the newer Z mainframes.
               | SABRE's multi-decade experience with IBM mainframes with
               | mission-critical business applications means they are one
               | of the world's foremost experts on its capabilities &
               | costs that's not biased by any IBM marketing or sales
               | pitches.
               | 
               | Even with all that in-house experience, SABRE still chose
               | to gradually migrate off of IBM mainframes to less
               | expensive tech stacks. Some have touted IBM's TPF
               | (Transaction Processing Facility) on the mainframe as
               | compelling technology but that still didn't dissuade
               | SABRE in ~2001 when they migrated the airfare pricing
               | application to Tandem (Compaq/HP) NonStop servers running
               | UNIX. (https://www.computerworld.com/article/1339621/has-
               | mainframe-...)
               | 
               | They then started a 10+ year effort to migrate more
               | mainframe workloads to Google Cloud. E.g. from
               | https://www.sabre.com/insights/a-journey-to-tackle-
               | legacy-co... :
               | 
               |  _> We moved 93% of compute capacity from physical data
               | centers to the public cloud, resulting in a 50% decrease
               | in our compute costs.
               | 
               | > We migrated more than 120 million bookings from a
               | mainframe-based system to one using Google Cloud's
               | Spanner database, without impacting customer operations.
               | _
               | 
               | JP Morgan Bank is another example of migrating from IBM
               | mainframes to cloud. If anyone out there truly thinks
               | that running a new greenfield Linux workload will be be
               | cheaper or even cost-competitive on a new IBM Z
               | mainframe, just pause and consider if you truly know
               | something about IBM mainframes' OpEx that multi-decade
               | IBM customers like SABRE and JP Morgan don't already
               | know.
               | 
               | Why would any new customers in 2025 willingly buy into
               | IBM Z mainframes if they see existing customers spending
               | billions trying trying to move off of them?
        
           | speed_spread wrote:
           | A mainframe is the biggest single system image you can get
           | commercially. It's the easiest, most reliable way to scale a
           | classical transactional workload.
        
             | rbanffy wrote:
             | > A mainframe is the biggest single system image you can
             | get commercially
             | 
             | It depends. As we have seen the other day, HPE has a
             | machine with more than 1024 logical cores, and they have
             | machines available to order that can grow up to 16 sockets
             | and 960 cores on a single image of up to 32TB of RAM. Their
             | Superdome Flex goes up to 896 cores and 48TB of RAM.
             | 
             | I believe IBM's POWER line also has machines with more
             | memory and more processing power, but, of course, that's
             | not the whole story with mainframes. You count CPUs that
             | run application code, but there are loads of other
             | computers in there doing a lot of heavy-lifting so that the
             | CPUs can keep running application code at 100% capacity
             | with zero performance impact.
             | 
             | > It's the easiest, most reliable way to scale a classical
             | transactional workload.
             | 
             | And that's where they really excel. Nobody is going to buy
             | a z17 to do weather models or AI training.
        
           | jareds wrote:
           | Do you have resources that provide info on companies using
           | Linux on Z and the benefits of this verses commodity
           | hardware? I used to work for a Mainframe ISV but the majority
           | of our software ran on z/OS. I only saw customers using Linux
           | on Z to begrudgingly run software that wouldn't efficiently
           | run on z/OS, mainly Java applications when customers didn't
           | want to deal with the complexity of specialty engines. I
           | realize because our software focused on z/OS I had limited
           | visibility into the full operations at our customers.
        
           | toast0 wrote:
           | > Depending on your workload there may be very good
           | economical reasons to consider a mainframe instead of a
           | number of rack-frames.
           | 
           | This may be true, but because there's basically no on ramp to
           | running on a mainframe, there's no way anybody is going to
           | try it unless they're already on a mainframe. Or maybe unless
           | they _really_ need something that only a mainframe can
           | provide. But most companies can live with some downtime, and
           | once you can live with some downtime, you have options for
           | migration between sites, and options for migrating loads so
           | you can swap parts on a stopped machine. Splurging on network
           | infrastructure with multi-chasis redundancy is an easier step
           | to take to get to a more reliable system than building
           | against a totally different system architecture.
        
             | timewizard wrote:
             | > This may be true, but because there's basically no on
             | ramp to running on a mainframe
             | 
             | You can get a partition of IBM Z to run in the cloud. The
             | cost is about $5/hr for the smallest configuration.
             | 
             | > Splurging on network infrastructure with multi-chasis
             | redundancy is an easier step to take to get to a more
             | reliable system than building against a totally different
             | system architecture.
             | 
             | Yes and no. If you truly need that redundancy than the
             | mainframe is going to provide a much better version of it.
             | SYSPLEXs and LPARs are some insanely powerful technologies.
        
         | NelsonMinar wrote:
         | My partner makes a living writing z/OS assembly language, has
         | been for many years now. The platform is still going strong as
         | a business. The main problem they face is all the folks who
         | know how to program these things are retiring (or dropping dead
         | at their keypunches.) It's very hard to convince new people to
         | learn how to operate these systems.
        
           | bityard wrote:
           | For your partner's sake I hope you're right but is z/OS as a
           | platform actually continuing to grow, or are they just having
           | a hard time filling seats because it's hard to see a long and
           | profitable future working on (what some might call) "legacy"
           | systems?
           | 
           | When I was growing up (decades ago, mind), my dad kept trying
           | to convince me to get into machining. Lathes, mills, tool and
           | die making, etc. In his line of work, he saw lots of
           | machining companies basically paying all education and
           | training expenses for new hires because their experienced old
           | timers were retiring faster than they could be replaced. (He
           | also thought computers were a fad...) I'm sure it was a good
           | opportunity at the time. But nearly all of those companies
           | eventually closed up because offshore manual labor was and
           | still is way cheaper. If I'd had taken his advice, I'm pretty
           | sure I would have had to reboot into another career at least
           | once by this point.
        
           | wglb wrote:
           | Interesting.
           | 
           | What sort of applications does your partner work on?
        
       | EncomLab wrote:
       | Alan Kay has promulgated many famous truths about computer
       | science - one of them being that among all fields of study, it
       | has the least regard for the people and discoveries that brought
       | it to where it is today. Maybe it's just my own sense of history
       | as I move into my 4th and likely last decade of working with
       | computers, but I find this to be both true and lamentable.
       | 
       | This was a great article - thanks for sharing!
        
         | bluGill wrote:
         | How many of the people who made the steam engine possible do we
         | remember? James Watt of course, but many many people were
         | making contributions in material science, needed to make them
         | useful. Not to mention many advances in values. No doubt lots
         | of other areas as well, but I'm no expert in the steam engine.
        
           | EncomLab wrote:
           | Not sure what you mean by this - it's not as if steam engines
           | are an extensive technology today, and certainly no
           | university is teaching "steam science", while nearly every
           | school is teaching "computer science".
           | 
           | Perhaps this is just the attitude that drives Mr. Kay's point
           | home - do individuals who are interested in CS have little
           | value for who and what has come before them?
        
             | CamperBob2 wrote:
             | To be fair, everybody who takes a thermodynamics course
             | owes 90% of it to the 'steam science' pioneers.
             | Understanding what determines and limits the efficiency of
             | heat engines was as big a deal in its day as the WWW is in
             | ours, but unlike our own era, a lot of brand-new science
             | and math had to be discovered by those engineers.
             | 
             | Steam tech is much, much more interesting than it appears
             | at first.
        
             | nancyminusone wrote:
             | Sure they do, it's just called fluid dynamics and
             | thermodynamics. Enough to fill up about 1/3 of a mechanical
             | engineering degree, if you're really into it (most aren't).
             | 
             | Not that there's a lot of historical context to things as
             | far as which people did what - most of that sort live on in
             | names of techniques and methods (Rankine cycle, de Laval
             | turbine, Carnot efficiency, etc.)
        
         | wglb wrote:
         | One example of this was the concept of virtual memory, which
         | was invented by Burroughs, not by IBM.
         | 
         | > as I move into my 4th and likely last decade of working with
         | computers
         | 
         | Don't despair--I am in my sixth and still program every day.
        
       | froh wrote:
       | TIL that not only the software side was chaotic (served as the
       | backdrop of Fred Brook's "Mythical Man Month"), but also the
       | hardware side almost failed.
       | 
       | the article here ends around 1971 --- the mainframe would later
       | save IBM again, twice, once when they replaced aluminum with
       | copper in interconnects, and then when some crazy IBM Fellow had
       | a team port Linux to s390. Which marked the birth of "enterprise
       | Linux", i.e. Linux running the data centre, for real.
        
         | mananaysiempre wrote:
         | > [Porting Linux to s390] marked the birth of "enterprise
         | Linux", i.e. Linux running the data centre
         | 
         | Did it though? Or was it the gradual phasing out of mainframe-
         | class hardware in favour of PC-compatible servers and the death
         | of commercial Unices?
        
           | rbanffy wrote:
           | > Or was it the gradual phasing out of mainframe-class
           | hardware in favour of PC-compatible servers
           | 
           | Proprietary Unix is still around. Solaris, HP-UX and AIX
           | still make money for their owners and there are lots of
           | places running those on brand-new metal. You are right,
           | however, that Linux displaced most of the proprietary Unixes,
           | as well as Windows and whatever was left of the minicomputer
           | business that wasn't first killed by the unixes. I'm not sure
           | when exactly people started talking about "Enterprise Linux".
        
             | kevin_thibedeau wrote:
             | Redhat was doing enterprise Linux well before IBM was
             | involved. It was the rational platform for non-legacy .com
             | 1.0 businesses.
        
               | rbanffy wrote:
               | Back then I went with Debian, but I agree - the early
               | scale-out crowd went mostly with Red Hat. Back then there
               | was a lot of companies still doing scale-up with more
               | exotic hardware with OSs like AIX and Solaris.
        
               | froh wrote:
               | nope.
               | 
               | the first enterprise Linux was SuSE on s390, then came RH
               | on x86 and then suse there as well. but RH marketing was
               | better back then already :-D
        
             | btilly wrote:
             | I first remember the term when Oracle ported themselves to
             | Linux, began submitting patches, then began pushing Oracle
             | on Linux to enterprises.
             | 
             | Oracle's big reason for doing so was because they could
             | charge more for Oracle on Linux, and still get to a lower
             | total cost of ownership than Oracle on Solaris.
             | 
             | Oracle began this in 1998. By 2006 they had their own
             | Oracle Enterprise Linux distribution.
        
           | froh wrote:
           | well, IBM very publicly invested 1Bn USD into supporting
           | Linux on all their hardware with all their software. so db/2
           | on s390 on Linux, likewise websphere, etc. it gave the
           | customers the promise of one run time environment on
           | anything. and SUSE and shortly later Red Hat provided truly
           | source compatible environments for software vendors. "code
           | once run anywhere", for real. and then IBM and Oracle and Co
           | forced suse and red hat to become binary compatible at the
           | kernel/libc and basic system libs level, so Oracle and all
           | could provide one binary under /opt on any Linux...
           | 
           | and that pulled all other vendors along, HP, Dell, Fujitsu,
           | likewise for software...
           | 
           | and it all started with IBM officially supporting and pushing
           | the hobbyist student project Linux on the holy Grail of
           | enterprise compute, (of 1999/2000): s390
        
             | sillywalk wrote:
             | > IBM very publicly invested 1Bn USD into supporting Linux
             | 
             | I remember Avery Brooks (DS9's Captain Sisko) doing a
             | commercial about IBM backing Linux in the year ~2000-ish.
        
       | cafard wrote:
       | Thomas Watson, Jr.'s _A Business and Its Beliefs_ was published
       | in 1963 and makes no allusion to the S /360 work. It makes for
       | curious reading today, for unrelated reasons.
        
       | scrlk wrote:
       | The IBM Centennial Film has a short interview with Fred Brooks
       | about System/360: https://youtu.be/VQ0PBve6Alk?t=84
       | 
       | Set to some nice Philip Glass music to boot.
        
       | herodotus wrote:
       | My Master's supervisor, at Wits university in Johannesburg,
       | worked on the architecture of the 360 after graduating from the
       | PhD program at Harvard. I remember him telling us how they went
       | about deciding whether or not 32 bits would be a sufficient size
       | for "most" floating point numbers. They were very systematic
       | about it, scouring journals, talking with physicists and
       | mathematicians and so on.
        
         | PaulHoule wrote:
         | (1) Maybe I'm just a little too young but my impression was
         | that the 360 and it's successors were not that big in
         | scientific computing, certainly there were some big academic
         | installations but I saw a lot more DEC machines (PDP-8 in the
         | experimental lab, PDP-10, PDP-11 and VAX elsewhere) and by the
         | time I went to college circa 1990 you were likely to see
         | Motorola 68k-based "workstations" that were quickly replaced by
         | RISC architectures like SPARC and PA-RISC which in turn failed
         | to compete with the PC.
         | 
         | Cornell had one of very few IBM 3090s with a vector unit (to
         | compete with the Cray) just before I showed up, but when I did
         | IBM had donated a message-passing based supercomputer based on
         | the Power PC architecture. I only saw a 3090 (no vector unit)
         | at New Hampshire Insurance which I got to use as a Computer
         | Explorer.
         | 
         | (2) I was taught in grad school in the 1990s to use floats if
         | at all possible to reduce the memory requirements of scientific
         | codes if not actually speed up the computation. (In the 1990s
         | floats were twice as fast as doubles on most architectures _but
         | not_ the x86). I really enjoyed taking a course on numerics
         | from Saul Teukolsky, what stood out in the class as opposed my
         | reading to the _Numerical Recipes_ book which he was a co-
         | author of, was the part about the numerical stability of
         | discretizing and integrating partial differential equations. If
         | you did it wrong, unphysical artifacts of the discretization
         | would wreck your calculation. Depending on how you did things
         | rounding errors can be made better or worse, Foreman Action 's
         | _Numerical Methods that Work_ and later _Real Computing Made
         | Real_ reveal techniques for managing these errors that let you
         | accomplish a lot with floats and some would point out that
         | going to doubles doesn 't win you _that_ much slack to do
         | things wrong.
        
           | wglb wrote:
           | > 360 and it's successors were not that big in scientific
           | computing
           | 
           | I do believe that is true.
           | 
           | IBM did have the Model 90 series, which was on the way to
           | being a supercomputer.
           | 
           | Bur during that time CDC with the 6400/6600 etc was likely
           | bigger in scientific computing.
        
             | hh2222 wrote:
             | The 360 played a pivotal role in the Apollo program.
        
       | svilen_dobrev wrote:
       | i have also found these to be interesting, kind of selection/
       | analysis/ visualisation over memoirs of Lou Gerstner (part 2 is
       | around s/360):
       | 
       | https://juliusgamanyi.com/2018/12/28/wardley-maps-an-illustr...
       | 
       | https://juliusgamanyi.com/2019/06/18/wardley-maps-an-illustr...
       | 
       | https://juliusgamanyi.com/2020/06/25/wardley-maps-illustrate...
       | 
       | Now, reading the article, this _" [rivalry].. So intense was it
       | that sometimes it seemed to exceed the rivalry with external
       | competitors."_ reminded me of something old about Motorola..
       | where rivalry went to the need to reverse-engineering other
       | depts' chips via 3rd party acquiring them..
       | 
       | www.chicagomag.com/Chicago-Magazine/September-2014/What-Happened-
       | to-Motorola/
        
       | kwanbix wrote:
       | As an ex-IBMer, I miss the IBM of old. So much innovation. Now
       | they are just a consulting company. So sad to see it go that way.
        
         | winrid wrote:
         | Indeed. Their current goal as communicated to shareholders is
         | literally to move all engineering offshore.
        
       | talkingtab wrote:
       | This whole thing is very cool and worth reading.
       | 
       | BUT. I worked at a place that used IBM 360s. We ran stuff for
       | engineers, a lot of Fortran along with assembly code. We had so
       | much stuff going on we could not code up and run things fast
       | enough. The engineer/scientist got frustrated.
       | 
       | Then one day an engineer brought in an Apple II from home and ran
       | the programs on that.
       | 
       | The earth shook. The very ground beneath us moved. Tectonic
       | plates shifted. The world was never the same again! I think it
       | was Visicalc.
       | 
       | Later there were other things. Soul Of A New Machine. The Mac.
       | 
       | I wonder how the compute power of a current high end smart phone
       | compares with and IBM 360? I know the graphics chip is better.
        
         | winrid wrote:
         | A $50 smartphone is many orders of magnitude faster.
        
         | PaulHoule wrote:
         | If I had to compare computers based on one number it would be
         | the amount of RAM. The 360 had a 24 bit address space which
         | could fit 16MB of RAM although only the largest installations,
         | like the one at NASA, were that big. iPhone 16s have 8GB of RAM
         | so you're talking 512 times the memory capacity, never mind
         | that my desktop PCs are all loaded with 4-8x times that of the
         | phone and you can definitely get a big server with a few TB.
         | 
         | An IBM 360/20 on the small side, however, ranged from 4kB to
         | 32kB which was similar to home computers circa 1980, before it
         | is routine to have a complete 64kB address space.
         | 
         | Where the 360 crushed home computers was in mass storage,
         | 9-track tapes could store 80MB contrasted to floppy disks that
         | stored less than 200kB. Large storage compared to memory meant
         | a lot of focus on external memory algorithms, also there was
         | already a culture of data processing on punched cards that
         | translated to the 360 (e.g. terminals have 80 columns because
         | punched cards had 80 columns)
        
           | kjs3 wrote:
           | _Where the 360 crushed home computers was in mass storage_
           | 
           | Well...sure, you could put bigger storage on a mainframe.
           | It's just money, after all. But you could put a tape drive on
           | a home computer. And bigger disks. And a card reader, for
           | that matter. Where the 360 _really_ crushed the home computer
           | was in aggregate bandwidth, via the Channel architecture. An
           | Apple 2 could just about keep up with a floppy and a display.
           | A 360 could keep up with dozens to hundreds of tapes, disks,
           | card readers, terminals, printers and other things all at the
           | same time.
           | 
           |  _Large storage compared to memory meant a lot of focus on
           | external memory algorithms_
           | 
           | I would agree with that. I would just argue the real
           | mainframe advantage is a whole-system one and not point to a
           | single factor (memory size).
        
         | kjs3 wrote:
         | >BUT. I worked at a place that used IBM 360s...Then one day an
         | engineer brought in an Apple II from home and ran the programs
         | on that.
         | 
         | The 360 was introduced in 1964. The 370 was introduced in 1970.
         | The 3033 was introduced in 1977. The Apple 2 was introduced in
         | 1977. So, yeah, if you were still using 360s contemporary with
         | an Apple 2, no wonder the engineers were frustrated.
        
         | btilly wrote:
         | _I wonder how the compute power of a current high end smart
         | phone compares with and IBM 360? I know the graphics chip is
         | better._
         | 
         | A current high end smartphone has around 10 billion
         | transistors.
         | 
         | From https://gunkies.org/wiki/IBM_System/360, IBM made 11-12
         | million SLT modules per year in the late 1960s, with less
         | before that. Each individual SLT module contained a handful of
         | transistors. Therefore, in transistor count alone, a single
         | smartphone has more transistors than IBM produced through the
         | 1960s. And this is before we consider the fact that clock
         | speeds today are much higher than they were in the 1960s.
         | 
         | Your smartphone literally has enough hardware to outcompute the
         | entire world circa 1970.
         | 
         | Isn't it amazing what over 50 years of Moore's Law can do?
        
           | btilly wrote:
           | Huh. The article claims at least an order of magnitude more
           | SLT modules than the reference I found. I think it is still
           | quite a bit less than the smartphone, but that makes global
           | compute at least closer.
           | 
           | Still, 55 years of doubling transistors at a given cost every
           | 2 years is about a 190 million fold transistor difference for
           | a given cost. Clock speeds have improved by a factor of 1000
           | on top of that. Even with performance tradeoffs for battery
           | life in a smartphone, there is no surprise that the phone
           | should have more compute power than the world did in 1970.
        
           | twoodfin wrote:
           | Indeed. I find it interesting to look at the generational
           | outliers on that curve: The Cray-1 wasn't eclipsed in raw FP
           | compute by a consumer system until the Pentium more than 15
           | years later.
           | 
           | http://www.roylongbottom.org.uk/Cray%201%20Supercomputer%20P.
           | ..
        
             | btilly wrote:
             | Most of the outliers look like, "Someone was willing to
             | spend large amounts of money."
             | 
             | Another outlier was Deep Blue. Estimated cost of about $10
             | million. Its estimated strength was matched by top end PCs
             | about 9 years later. Your phone today is better than those
             | PCs.
             | 
             | Progress is relentless.
        
           | kstrauser wrote:
           | My home NAS in the other room could hold about 350 million
           | C64 floppies. I've sometimes wondered how that compares to
           | the world's floppy disk manufacturing capacity in 1982.
           | 
           | I also appreciate that my Internet connection is about 33
           | million times faster than my first modem. It'd take me over a
           | year to download what I can slurp in about 1 second now, even
           | if I could afford the 7 thousand floppies it'd take to store
           | it.
           | 
           | Progress, yo.
        
         | Pet_Ant wrote:
         | How many years old was the s/260 at this point? If it was
         | really long in tooth then I wouldn't be surprised.
        
         | chasil wrote:
         | The 360 had 24-bit addressing, for a maximum of 16 megabytes.
         | 
         | The 6502 in the Apple could address 64k of RAM. Any class of
         | problem requiring more memory would need a real machine.
         | 
         | As far as a personal machine with comparable capability, RISC
         | brought that to the market with the first MIPS R2000 in 1985.
         | 
         | https://en.wikipedia.org/wiki/MIPS_architecture
        
           | spc476 wrote:
           | The Motorola 68000, introduced in 1979, had 24 address lines.
           | The Intel 80286, introduced in 1982, also had 24 address
           | lines.
        
             | chasil wrote:
             | Well, the VAX was there before any of these, but I wouldn't
             | call that a "personal machine."
             | 
             | I suppose the argument could be made that the 68000 was
             | first, as both it and MIPS ended up in gaming consoles
             | (Sega Genesis vs. Sony PS2 and Nintendo 64).
             | 
             | However, MIPS eventually scaled to 64-bit, was well-known
             | and heavily exploited in supercomputing applications, and
             | was used to produce the film _Jurassic Park_. The 68000 had
             | a far dimmer future.
             | 
             | Yes, the x86 line did supplant them all, but only with
             | AMD's help. Had Itanium been Intel's final answer, MIPS
             | might be much stronger today.
        
       | ChicagoDave wrote:
       | My sister worked at IBM and one of my favorite stories is when
       | Lotus tried to pressure IBM to spend millions on licensing, a few
       | engineers went off and built their own spreadsheet application
       | and IBM told Lotus to piss off.
        
       | Synaesthesia wrote:
       | And this is all before integrated circuits, so the circuits are
       | still very large, consisting of many circuits on boards mounted
       | on a backplane.
       | 
       | https://en.wikipedia.org/wiki/IBM_System/360#Basic_hardware_...
       | 
       | https://en.wikipedia.org/wiki/Solid_Logic_Technology
        
       | SoftTalker wrote:
       | The reason the tape drives are in those tall enclosures are the
       | vertical channels below the tape reels. That was for slack in the
       | tape, there was a loop of tape hanging in each of the channels,
       | so that tape reads and writes could be stopped and started faster
       | than the heavy tape reels could stop and start.
        
         | Henchman21 wrote:
         | This is super interesting to me, thanks for that. Are there any
         | other hidden but well-known things like that?
        
       | shrubble wrote:
       | To add to this: they had $750 million in 1963 dollars, in parts
       | and no shipping computers; inventory control was so bad that they
       | had to have guys with clipboards to physically go into the
       | warehouse and count parts.
       | 
       | They announced it and started getting a huge number of orders;
       | IBM hired 1000 people a month and kept up that pace of hiring for
       | 5 years.
        
       | RazorDev wrote:
       | Fascinating look at the challenges and risks IBM took on with the
       | System/360. Betting the company on a compatible mainframe family
       | was visionary but nearly disastrous. It's a testament to the
       | importance of strong technical leadership, teamwork and
       | perseverance to bring revolutionary products to market.
        
         | skmurphy wrote:
         | It was a business decision driven by Tom Watson Jr. after
         | listening to a lot of customer feedback. See "Father, Son, and
         | Co." https://www.amazon.com/Father-Son-Co-Life-
         | Beyond/dp/05533808... his autobiography of his years at IBM,
         | and beyond. The 360 project figures prominently.
        
       | JJMcJ wrote:
       | The well known book "The Mythical Man Month" is in large part
       | based on the author's experience as one of the top people on the
       | System 360 project, and what went wrong during the effort.
        
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       (page generated 2025-04-08 23:01 UTC)