[HN Gopher] Comparing the 1970's Cray-1 supercomputer against th...
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Comparing the 1970's Cray-1 supercomputer against the Raspberry Pi
Author : mywacaday
Score : 80 points
Date : 2024-01-19 00:00 UTC (23 hours ago)
(HTM) web link (blog.adafruit.com)
(TXT) w3m dump (blog.adafruit.com)
| klelatti wrote:
| Nothing against AdaFruit, but this really should link to Roy
| Longbottom's detailed comparisons [1] that this very short post
| links to.
|
| [1]
| http://www.roylongbottom.org.uk/Cray%201%20Supercomputer%20P...
| milliams wrote:
| Specifically, the Raspberry Pi section at
| http://www.roylongbottom.org.uk/Cray%201%20Supercomputer%20P...
| pge wrote:
| And the HN discussion of that link -
| https://news.ycombinator.com/item?id=38758355
| klelatti wrote:
| Oh wow! Thanks, that's a great discussion.
| dang wrote:
| Thanks! Macroexpanded:
|
| _Cray-1 vs Raspberry Pi_ -
| https://news.ycombinator.com/item?id=38758355 - Dec 2023 (180
| comments)
| jacquesm wrote:
| Indeed, it's a reblog of a reblog of an absolutely excellent
| article.
| Fnoord wrote:
| The article mentions "See Longbottom's extensive tests and
| comparisons article here." and [1]. This was already mentioned
| in a snapshot of 18 Jan 2024 [2] so it wasn't added after your
| criticism.
|
| [1]
| http://www.roylongbottom.org.uk/Cray%201%20Supercomputer%20P...
|
| [2] https://archive.is/a99i3
| klelatti wrote:
| No criticism of AdaFruit intended. I meant the HN link should
| be to the original article - the post that I say the AdaFruit
| post links to.
| jacquesm wrote:
| They meant the link at the top here.
| jermaustin1 wrote:
| This is actually mildly surprising to me that the Raspberry Pi is
| only 4.5x faster. I would have bet 10-20x faster just because of
| how much time has passed and all the talk about: "your cellphone
| is 1000x faster than the Apollo computers" that I've been hearing
| since the time of the t-mobile sidekick.
|
| I've always taken them with a grain of salt, but even if they
| were only an order of magnitude off, a Pi is loads faster than a
| sidekick. And sure the Cray is loads faster than the Apollo
| computers, but I wouldn't have thought it was THAT much faster.
|
| I am amazed.
| snek_case wrote:
| The Cray 1 was way ahead of its time. It implemented SIMD
| vector instructions to speed up numerical computation, was
| liquid cooled, and ran at 80 MHz (in 1976). The chief
| architect, Seymour Cray, was kind of a genius, and is
| responsible for designing many other pioneering machines.
|
| Also, fun fact, it didn't have a CPU. It used all discrete
| logic chips, and was wired by hand, with lots and lots of wire.
| IIRC Seymour Cray liked to hire women to do the wiring job,
| because they had an easier time fitting inside the computer
| core to wire it, and doing detailed work because they had
| smaller hands.
| msla wrote:
| > Also, fun fact, it didn't have a CPU. It used all discrete
| logic chips, and was wired by hand,
|
| That's how CPUs were built back then. What it didn't have was
| a single-chip CPU, or a microprocessor.
|
| Next up: "The Model T Ford didn't have an engine, it had this
| gasoline-burning device to provide motive power."
| drfuchs wrote:
| Lots and lots of wire, yes, with each one cut to a specific
| length so that all of each gate's input signals arrive at the
| same time. That's why the backplane looks like a mess of
| wires hanging down due to seemingly being way too long.
| dragontamer wrote:
| Note that modern RAM has length matched traces.
|
| Take a look at all the PCB traces near RAM and CPU. You can
| see them 'squiggle' looking for matching-space at either
| end of the RAM/CPU connection.
|
| PCBs make things like consistent length matching easier.
| All circuit boards have near identical lengths, controlled
| impedances and other features that support ... Well...
| Effectively 6-billion baudrates for DDR5.
|
| 6000Mhz DDR5 with 64-bits per half-clock (3000Mhz clock so
| 6000 transfers per second) has a bit every 5 centimeters or
| so.
| whizzter wrote:
| And that kinda makes it unfair to the Raspberry, maybe not
| the RPI1 but I'm pretty sure that the RPi4 (rated at 78x the
| Cray) running code in compute-mode would thrash the Cray 1
| even harder (yes, not entirely comparable but since you
| probably didn't get full throughput on the Cray with regular
| C code then using the GPU on the RPi should be fair game).
| peterfirefly wrote:
| > SIMD vector instructions
|
| Err...
|
| That term is used to describe modern vector instructions that
| are NOT vector instructions in the classical Cray-sense.
| Modern CPUs use wide registers that can be regarded as
| vectors of 2/4/8/... values. Cray used memory-to-memory
| variable-length vectors.
|
| I'm not saying that "SIMD vector instructions" is an
| incorrect description of what the Cray machines did, I'm
| saying that the term usually means something else today.
| robin_reala wrote:
| The Cray-1 was ~160,000,000 FLOPS. The Apollo Guidance Computer
| was about 14,000 FLOPS, so about 11,500x slower.
| jermaustin1 wrote:
| I guess it was THAT much faster. That is an insane leap in
| performance in a decade. I know they are apples and oranges.
| One weighed about 150x more than the other, but still such a
| surprise to me.
| jacquesm wrote:
| Seymour Cray was absolute genius. There are so many
| innovations in the Cray-1 that you could easily write a
| book about it.
|
| edit: some searching later:
|
| https://www.goodreads.com/en/book/show/116196
| knorker wrote:
| They're not just apples and oranges, but apples vs
| differential equations. They had completely different
| requirements. Like ROM being sown for Apollo.
|
| You get something completely different if failure is not an
| option.
|
| But also yes, it is a big leap. NASA bootstrapped the
| semiconductor industry by buying up most of the world's
| supply. Without the Apollo program we may only just now
| have gotten smartphones. (And some people still think it's
| a waste of money. pff!)
| beerandt wrote:
| Yeah, primarily minimize weight and power while meeting
| compute requirements. Excess compute in this case is bad
| design.
|
| The cray was 10,000 lb and 115 kilowatts. Not payload
| friendly.
|
| I'm imagining Kevin Bacon doing his Apollo 13 power
| budgeting scene, but needs another ~114kw.
| knorker wrote:
| Gary Sinise. Kevin Bacon had already had the measles, so
| he took his place. :-)
| jacquesm wrote:
| > And some people still think it's a waste of money.
|
| Some of those people are right here. The number of times
| I've seen the 'whitey on the moon' nonsense is quite
| large.
|
| https://hn.algolia.com/?dateRange=all&page=0&prefix=false
| &qu...
|
| And probably most of those people don't realize they
| wouldn't be posting anything at all if not for 'whitey on
| the moon', the Apollo program era started with sliderules
| in 1962 and ended in 1972 with functional microcomputers
| (8008, 1972, shortly followed by the 6502, 1975) and a
| very short while later we had programmable pocket
| calculators (Ti59, 1977). The whole semi conductor
| industry was jumpstarted in those years.
|
| When I first started out with electronics transistors
| were an absolute rarity and tubes were normal, in the
| space of a decade that changed completely.
| myrmidon wrote:
| > NASA bootstrapped the semiconductor industry by buying
| up most of the world's supply. Without the Apollo program
| we may only just now have gotten smartphones.
|
| I strongly disagree with that. The semiconductor industry
| was thriving before NASA even existed, none of the
| central enabling inventions (MOSFET transistors,
| semiconductor manufacturing techniques) were made there
| or even related to the Apollo program, and "computers" as
| in turing complete machines already existed before NASA
| and had plenty of applications apart from space travel.
|
| NASA/Apollo giving todays smartphones a 10 year
| technology boost is just pure fiction and not even
| remotely supported by facts.
| knorker wrote:
| We can't do an A/B with history, but I'm basing it on
| things like:
|
| > By the mid-1960s, according to the PBS documentary,
| NASA was buying 60 percent of the integrated circuits
| produced in the United States. Fairchild was a major
| supplier, shipping about 100,000 devices for the Apollo
| space program in 1964 alone.
| peterfirefly wrote:
| It's right up there with velcro and teflon.
| unregistereddev wrote:
| Not only did the Cray weigh far more than the Apollo
| computer, and not only did the Cray supercomputer use far
| more power, but the Apollo computers had to be designed to
| be highly resistant to interference from radiation.
|
| Radiation hardened electronics are fascinating to me. To
| this day, electronics that function in outer space are much
| slower than datacenter or consumer-oriented components.
| tass wrote:
| You're not wrong, since the 4.5x number comes from a comparison
| with the rPi 1.
|
| The rPi 4 is over 10x faster than the 1.
|
| The original article points out that the raspberry pi 400, with
| the benchmark targeting 64 bits, was about 80x Cray for the
| same benchmark which was 4.5x for the rPi 1.
|
| Raspberry Pi 5 advertises a 2-3x performance gain over earlier
| versions, though this wasn't benchmarked in these tests.
| postmodest wrote:
| Aren't these also in FLOPS? The rpi isn't exactly a floating-
| point monster. Hell, until the Pentium, Intel CPU's weren't
| guaranteed to even have an FPU.
|
| As to ARM in general, here's a post about how ARM-1 compared
| to the 387: https://retrocomputing.stackexchange.com/question
| s/24826/did...
| justin66 wrote:
| > Hell, until the Pentium, Intel CPU's weren't guaranteed
| to even have an FPU.
|
| 80486
| peterfirefly wrote:
| 486SX
| justin66 wrote:
| The 80486SX was introduced two years after the 80486 and
| did _not_ have an FPU (unless it was purchased as an
| option).
|
| I think the meaning of my comment was clear: the 80486
| was the first Intel CPU guaranteed to have an FPU. I
| didn't say all the Intel CPUs which came afterward were
| guaranteed to have them...
| postmodest wrote:
| My first "my own purchase" PC was a 486sx. So as a
| _line_, "the 486" wasn't guaranteed to have an FPU.
| bee_rider wrote:
| It is against a Pi 1.
|
| It looks like the Cray gets a bit of a boost from the linpack
| scores (the pi is only 1.6x faster!), which is a good test for
| the Cray (understatement!).
| flavius29663 wrote:
| Apllo was not the fastest computer in the world. It was a small
| device enough to shuttle rockets around the moon and back.
| DonHopkins wrote:
| The Cray-1 has better upholstery.
| eropple wrote:
| Can't sit on a Raspberry Pi. What's even the point?
|
| Well, alright, you can sit on one once.
| rescbr wrote:
| You can sit on one many times, it's small enough that your
| weight is distributed over it by your own buttocks :)
| rob74 wrote:
| ...but imagine the computing power if you cram all the empty
| space under your couch full of Raspberry Pis! You could have
| _hundreds_ of Crays in there!
| nerdbert wrote:
| Someone's working on that.
|
| http://www.clustered-pi.com/blog/clustered-pi-zero.html
| coldpie wrote:
| My dad worked in Facilities at the Minnesota Supercomputer
| Center (or maybe it was Cray, or maybe it was Control Data, or
| maybe it was NetASPx, or maybe it was something else, I was
| never clear to be honest) here on Washington Ave in
| Minneapolis. Sometimes as a kid in the 90s, he'd take me in to
| follow him around for a day. I definitely remember looking at
| the server racks and supercomputers they had on their main
| floor, watching automated tape backup machines move tapes
| around, all these crazy water cooling setups with colored
| lights, stuff like that. I even got to see the big diesel
| backup generators in the basement once. But the standout was
| the decommissioned Cray-1 they had as a seating bench in the
| front lobby. Could walk inside the unit and look at all the
| wires and circuit boards connected together, or just sit on the
| nice padded bench and have a chat. If you really knew what you
| were doing, you could lift up the seat panels and have a look
| at more boards and wires. Fun stuff.
| mytailorisrich wrote:
| > _"The Raspberry Pi ... is more than 4.5 times faster than the
| Cray 1."_
|
| The applications have grown as well.
|
| The Cray 1 was used for mundane tasks like " _large-scale
| scientific applications, such as simulating complex physical
| phenomena, and was sold to government and university
| laboratories._ " [1] But the power of the Raspberry Pi allows for
| cutting edge computing tasks like " _watering plants, monitoring
| the birds in your yard, or for a smart doorbell!_ " [2]
|
| [1] https://www.britannica.com/topic/Cray-1
|
| [2] https://picockpit.com/raspberry-pi/the-7-most-common-uses-
| fo...
| reaperducer wrote:
| I know it's only January, but this strikes me as Comment of the
| Year.
| flenserboy wrote:
| Imagine the pain of programming a Cray-1 to do the work of a
| Raspberry Pi in those use instances.
| bombcar wrote:
| Or using a Raspberry Pi to simulate nuclear explosions and
| the weather.
| d_sem wrote:
| The absurdism to having a replica Cray-1 for the sole purpose
| of watering my plants is too amazing to not entertain.
| aw4y wrote:
| the main difference is that I cannot hold 10 crays in my desk
| drawer waiting to use them :P
| Frenchgeek wrote:
| https://www.chrisfenton.com/homebrew-cray-1a/ (You'll still
| need a pretty big drawer)
| spintin wrote:
| We now have a C64 as powerful as the Cray-1 is what you could say
| if you traveled back in time.
| antirez wrote:
| Am I the only one that is shocked by the fact that a 1978
| computer, even if a supercomputer (but still using the technology
| of the time) was 1/4 the speed of a Raspberry? The Pi, if you
| look at the big picture of computing, is a very fast computer.
| For comparison: you can run a 1 billion parameters LLM on a
| Raspberry pi at decent speed. This means that the Cray could run
| it, even if slowly. That's incredible.
| throwbadubadu wrote:
| Find it similarly amazing, yes.
|
| > This means that the Cray could run it
|
| Gladly, we had better things to do than that :D
|
| But seriously, while we could have run it maybe speedwise, it
| definitely lacked the memory, not? And if one tried to train it
| he wouldn't be finished today. But would make a fun backwards
| sci-fi story imagining a time traveller that brought the 80ies
| an LLM from today, what would the world say and do with that
| slow oracle?
| samstave wrote:
| May you please do me (and others) a favor:
|
| What value does an LLM hold intrinsically.
|
| Lets say "brought an LLM from today"
|
| Does that mean just a multi gig file? What is INSIDE the LLM
| that would be of value? How does one speak to an LLM WRT 80's
| tech, and what could one glean from it....
|
| ELI5 an LLM;
|
| BARD: https://i.imgur.com/ahRVECz.png
|
| OpenAI: https://i.imgur.com/Rbk5BD6.png
|
| Bing: https://i.imgur.com/zVJ1tu6.png
|
| --
|
| So, how would one explain 80s folks what even an LLM is when
| we cant even ELI5 2024?
| LeoPanthera wrote:
| In a way that someone in the 80s could understand?
|
| An LLM is a very highly compressed store of knowledge
| combined with an advanced parser than understands questions
| in plain English. A consequence of the compression is that
| sometimes the answers lose some accuracy, which is a
| deliberate trade-off to make it work at all.
| samstave wrote:
| Now paint me a picture of a cat. Good LLM.
| NikkiA wrote:
| Neural networks were known about in the 80s, they were
| theorised about in the 1800s ffs, and the first computer
| based NNs were in the 1950s.
| throwbadubadu wrote:
| My story plot would sure include LLM (coefficients file as
| today) + code to run it. So 80s humans could run it on the
| Cray, ask it questions, and get answers (after some time
| :D).
|
| LLM could explain itself what it is.. (if there are not
| more important questions to ask, contention would ensue).
| bee_rider wrote:
| I don't think they'd have any trouble with the math, it's
| just a bunch of regressions and matvecs, right?
|
| I think the process of collecting and storing all the data
| would be more mind blowing to them--of course they were at
| the beginning of Moore's law, so they could see the
| trajectory if they looked for it, but it is one thing to
| stand on the coast with waves lapping at your ankles and
| imagine how the ocean gets deeper as you keep going and
| another to get chucked out of a helicopter in the middle of
| the Pacific.
| d0mine wrote:
| LLM is a lossy compression of the internet. We can provide
| it in a form that is directly executable on 80s computers
| though gpt4 tries to convince me that it is practically
| impossible the reduced model would be much weaker (somebody
| doesn't want to be sent to 80s ;)
| dekhn wrote:
| I can't find it now but I wrote a bit of fanfic where Ken
| Thompson sent an LLM back in time (referencing his "Love,
| Ken" UNIX tapes that he would send out) to save humanity. He
| was always a bit head of his time.
| klelatti wrote:
| Would we have been able to train the LLM in the first place
| though? Guessing that that would have been completely
| infeasible?
| samstave wrote:
| This guy Time Travels. (check his hands, he likely has extra
| fingers)
|
| But... lets look at the availability of DATA in the 80s..
|
| Frankly, this is how hacking/phreaking was invented.
|
| Dumpster-diving for line-printer discards in dumpsters to
| understand what their systems did.
|
| (This is an actual story; people were bin dipping (at&t?)
| dumpsters and finding exploits (social or electronic) in the
| discarded line-printer outputs....
|
| Can someone validate that comment?
|
| --
| r3trohack3r wrote:
| This spirit appears to be alive and well.
|
| Brian Roemmele says they've been dumpster diving for
| decades salvaging huge collections of microfilm/microfiche
| that's been thrown out by libraries, research institutions,
| etc.
|
| Now that LLMs are here, they're taking that collection and
| training an LLM against it (instead of the internet): https
| ://twitter.com/BrianRoemmele/status/1746945969533665422
| bombcar wrote:
| The supercomputers of the time were very heavily designed to
| run floating-point operations (IIRC) and so while the FPU
| performance might be comparable, I'm not sure a Cray could be
| used as a "1/4 speed Pi" for general computing things like
| running Linux.
| criddell wrote:
| I used a Cray around 1998 (from the Pittsburgh Supercomputing
| Center IIRC) and it was super fast on very particular tasks.
| Specifically, there was some type of processing pipeline that
| once you had it set up, it would produce a stream of
| calculations very quickly.
|
| I wonder if the Raspberry Pi is faster on all tasks, or is
| there some type of computation the old Cray is still
| competitive?
| bombcar wrote:
| I suspect the Cray is "competitive" for some value of
| "doesn't absolutely stink" for things that are designed for
| it.
|
| But you can emulate a Cray on an FPGA:
| https://www.chrisfenton.com/homebrew-cray-1a/ so I suspect
| that while it could still do "real work" you can also beat
| the pants off it if you setup your code as designed to run
| on modern GPUs.
| d_sem wrote:
| Remarkable, yes. Shocking, no. Exponential growth was something
| experience in the computer industry for decades, and people
| where quite normalized to it.
| thoughtsimple wrote:
| That was on a 700 MHz Raspberry Pi 1. On an 1800 MHz Raspberry
| Pi 400 NEON SIMD the difference was another order of magnitude.
|
| [QUOTE] Comparison - The three 700 MHz Pi 1 main measurements
| (Loops, Linpack and Whetstone) were 55, 42 and 94 MFLOPS, with
| the four gains over Cray 1 being 8.8 times for MHz and 4.6,
| 1.6, 15.7 times for MFLOPS.
|
| The 2020 1800 MHz Pi 400 provided 819, 1147 and 498 MFLOPS,
| with MHz speed gains of 23 times and 69, 42 and 83 times for
| MFLOPS. With more advanced SIMD options, the 64 bit compilation
| produced Cray 1 MFLOPS gains of 78.8, 49.5 and 95.5
| times.[/QUOTE]
| mrb wrote:
| "1/4 the speed of a Pi" applies to the original (slow) 2012 Pi
| which is unable to run LLM as fast as you think. However the
| 2020 Pi 400 (equivalent to Pi 4), which can run the LLM
| workload, is about 100 times faster than the Cray 1:
|
| " _Raspberry Pi ARM CPUs - The comment above was for the 2012
| Pi 1. In 2020, the Pi 400 average Livermore Loops, Linpack and
| Whetstone MFLOPS reached 78.8, 49.5 and 95.5 times faster than
| the Cray 1._ "
| http://www.roylongbottom.org.uk/Cray%201%20Supercomputer%20P...
|
| A Pi 4 can infer ~0.8 tokens/sec with some of the more
| optimized configs (as per
| https://www.dfrobot.com/blog-13498.html). So the Cray would
| have needed ~2 minutes per token, so ~2.5 hours to generate one
| sentence... if hypothetically it had enough RAM (it didn't).
|
| In 1978 RAM cost about $25k per megabyte
| (https://jcmit.net/memoryprice.htm). Assuming you needed 4GB
| for inference, RAM would have cost $100M in 1978 dollars, or
| $470M in today's dollars.
|
| For comparison, the Cray cost $7M in 1978 which is $32M in
| today's dollars. So once you buy a Cray you would have had to
| spend 14 times that amount on building a custom RAM device
| extension of 4GB, somehow hooked to the Cray, to finally be
| able to generate one sentence every 2.5 hours...
|
| But in 1978, even if RAM was available to do LLM inference, it
| would have been impossible to train the model, as vastly more
| compute power is needed than for inference.
| GartzenDeHaes wrote:
| The other factor is RAM, which is more problematic. The Cray-1
| had up to 4 Meg WORDS RAM, or 2 Meg as we would measure today
| (I think).
| otabdeveloper4 wrote:
| Cray was 64 bit, IIRC, so 4 megawords would be 32 megabytes.
| kevin_thibedeau wrote:
| The shocking thing is that every contemporary PC and handheld
| device would place on the TOP500 list in the 90's yet they're
| still burdened with slow software when doing basic operations.
| rightbyte wrote:
| Ye my fastest computer I will ever own was a Pentium 200MHz
| with 32Mb of ram running Windows 95.
| JeffSnazz wrote:
| Given that it also functioned as sort of an uncomfortable couch
| --not really.
|
| Besides, it's way further behind in basically every respect but
| compute.
| dahart wrote:
| Another really fun Cray comparison: Turner Whitted ("father of
| ray tracing") is rumored to have speculated some time back when
| he first published on ray tracing that in order to do real time
| ray tracing, you could put one Cray supercomputer per pixel out
| in the desert, each one with a single colored light, and view it
| from an airplane, and that would be roughly enough compute to
| achieve real time.
|
| A 4090 today is roughly 500,000 times faster, which means we now
| have achieved one Cray per pixel (!) for an 800x600 image
| (smaller than images today, but maybe a bit larger than the
| average image size in the late 70s).
| RicoElectrico wrote:
| To be honest our real-time RT works only because we're
| "cheating" with denoisers working in spatial and temporal
| domain.
| corysama wrote:
| Sure, to get Cyberpunk 2077 at 4K 60FPS, we cheat like hell.
| But, a scene from 70s ray tracing research at 800x600x24 fps
| on a 4090 doesn't need to cheat much.
| dahart wrote:
| In a way, yes, partly because we're rendering typically
| larger images now (1080p is 4x larger than 800x600), but also
| because the image quality standards are very high, and
| because scenes are enormous compared to a pair of spheres and
| a checkerboard plane with a single light, because games don't
| get to spend the entire frame budget on rays, and because
| we're using a lot more stochastic sampling now using path
| tracing than what Turner Whitted did. We do get the 500,000x
| relative to Cray, and denoising effectively adds another
| x-factor on top of that, and that's what it takes to get
| today's games up to passable real time ray tracing. On the
| other hand, genuine real-time ray tracing without denoising
| has been possible for a long time for toy scenes outside of
| games, it all depends on what goal posts we're talking about
| exactly, right?
| dekhn wrote:
| I have not... heard that idea before. Instead, I heard "reality
| is just 100 million polygons per second" (Jim Clark?), implying
| that if you can do ray tracing at a high resolution and frame
| rate, you can fool somebody's optical nerves into thinking they
| are looking at reality (ignoring the difference between pixel
| screens and the physics of how human vision actually works).
|
| Does anybody have a reliable link to the Whitted quote?
| dahart wrote:
| My source for the story is indirect, via Steve Parker, who's
| worked with Turner.
|
| https://www.youtube.com/live/LUFp6sjKbkE?si=8vcxo-Vp8oeRUnob
|
| Scrub to 3:52:19 for the Turner Whitted story.
|
| BTW, mostly unrelated, but scrub that video to 5:47:10 for an
| amazing talk by Ivan Sutherland ("father of computer
| graphics") that is not about graphics (he politely refuses to
| talk about graphics anymore :P), but about the active
| research he's been doing (at 85 years old) into Single
| Quantum Flux circuits (an alternative to CMOS).
|
| Also- Jim Clark at 4:48:40
|
| Jim's idea you mention is still correct & compatible with
| Turner's idea. Jim's point is that we only need to render
| finite pixels. You might need an x-factor more triangles than
| pixels because of sampling and depth complexity and secondary
| lighting, so 100M polys is probably in the ball park, as long
| as we can quickly pick the _right_ 100M polys in real time...
|
| In a way, Turner was talking about a lower bound, while Jim
| is talking about an upper bound, albeit slightly different
| things but they are similar, both relate to how much compute
| is needed for real time rendering.
| dekhn wrote:
| Thanks for the timestamps. Great to see Ivan breaking
| ground in another area, his contribution to early graphics
| and interactive computing is still amazing today.
| agumonkey wrote:
| There was a comment on .. slashdot or similar, where someone
| explained that the massive L0 cache of the CRAY (8MB ?) meant it
| could sustain it's "limited" throughput, whereas an intel quad
| core would peak above then plummet due to spilling.
| jecel wrote:
| Cray didn't believe in caches or virtual memory. He felt that
| data placement and movement should be 100% in the programmer's
| control.
|
| 8MB was the main memory, but it was made from really high speed
| (and super expensive!) static RAM chips instead of the dynamic
| RAMs most other machines used. Other machines used SRAMs for
| caches, so I guess you could consider the Cray 1's main memory
| to be a cache.
|
| The Cray had 8 "A" address registers but also 64 "B" registers.
| In the same way you had 8 "S" scalar registers plus 64 "T"
| registers. The main memory was highly interleaved so you could
| very quickly load and save blocks of B and T registers as well
| as the vector registers. You can think of B as a sort of cache
| for A and T as a sort of cache for S, but you had to explicitly
| handle this in your program.
| taf2 wrote:
| I'm pretty sure it was here that I read how cray would drive on a
| family trip and insist the kids stay silent while he drove and
| designed much the cray in his head on the drive... if anyone has
| a link would love to re read that story
| parshua wrote:
| Now imagine a Beowulf cluster of those Raspberries!
| juggertao wrote:
| > The first PC to reach the average Cray 1 Livermore Loops score
| is indicated as a 1994 100 MHz Pentium
| hn8305823 wrote:
| Nooooo! You can't compare a Cray vector processor to a general
| purpose Raspberry PI!
|
| https://imgflip.com/i/8cwqf1
|
| Seriously though, I think the fact that the PI is general purpose
| makes it even more impressive.
| NoZebra120vClip wrote:
| Some advantages of Cray also included the fact that your
| purchase/commission included a cadre of support guys who would
| pretty much immediately show up with replacement parts and slide
| logic boards in/out until your system was repaired. This sort of
| service speaks to both the kind of modularity that we've lost
| with SBCs, as well as the enterprise service levels available
| with high-end equipment like that.
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