[HN Gopher] More than two hard disks in DOS
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More than two hard disks in DOS
Author : yuhong
Score : 47 points
Date : 2025-08-05 11:19 UTC (11 hours ago)
(HTM) web link (www.os2museum.com)
(TXT) w3m dump (www.os2museum.com)
| philipstorry wrote:
| Quite the nostalgia blast for me!
|
| I'm honestly not sure I had a machine with more than 2 fixed
| disks until well into the days of Windows 7 and SATA. The
| exception would be logical disks such as Stacker or similar
| compressed volumes - but I wasn't using them until later either.
|
| If I recall correctly before SATA we had IDE which only had two
| devices (primary & secondary) per controller, and usually only
| two controllers on a motherboard. Given the physical size of
| disks even you'd probably just have a boot disk, maybe a data
| disk and then perhaps two optical drives. So it's absolutely
| believable that nobody found the bug simply because nobody had a
| machine configured that way.
|
| Sure, you could have SCSI for more disks. But if you did, then
| you were probably doing something that required a lot of CPU
| grunt - at which point you might just leave the PC behind and go
| to a UNIX workstation anyway.
|
| OK, now I'm starting to get flashbacks to just how bad SCSI
| support was on the PC, and it's stripping the the rose-tint from
| my glasses. Time to go!
| jmclnx wrote:
| I had added a 2nd disk on my 386sx, but I guess it was after
| the DOS 5.0 time. I did not realize before v5 it was not
| allowed.
|
| Not long afterwards I ended up on Coherent OS, fun times.
| pjmlp wrote:
| And expensive, really expensive.
| lenerdenator wrote:
| I was gonna say, " _MORE THAN TWO HARD DISKS? IN THE DAYS OF
| DOS?!_ Anything else we could get for you, your majesty? "
| forinti wrote:
| I have piles of old, but still functioning HDs now. I was
| looking at them yesterday and thought about how cheap these
| things have become.
|
| I had to save up to buy floppies in the 80s!
| rwmj wrote:
| Not to mention the weight, power demands and (to some extent)
| noise!
|
| At one point I did have two hardcards plugged into my Amstrad
| 8086 machine which felt pretty decadent. (Or maybe it was a
| hardcard plus the internal hard drive?) In total it wasn't
| even 100MB of storage. https://en.wikipedia.org/wiki/Hardcard
| cestith wrote:
| That, and the IBM PC 5150 had what, 130 watts?, in the
| stock power supply.
| dardeaup wrote:
| There were also MFM and RLL hard drives. I don't recall if they
| were pre-IDE or something different altogether. It's been a
| long time.
| mrspuratic wrote:
| I used MFM in the first PC I built from scavenged parts, it
| used an ISA MFM controller card. IDE came later, those had an
| integrated controller ("integrated drive electronics") so the
| PC didn't need to know how to do the low-level control for
| the drive. Luxury. And less jumpers to faff about with.
| c0nsumer wrote:
| Yes they were. IDE stands for Integrated Drive Electronics
| because the drive could be connected directly to the ISA bus,
| using an on-board controller, vs. having to use an MFM or RLL
| controller on the bus in between it and the disk.
| cestith wrote:
| Also ESDI.
| Telemakhos wrote:
| > before SATA we had IDE
|
| I had the original IBM PC with two 5.25" floppy drives, and I
| think that was all the room there was on the disk controller.
| Dad bought a 10MB Hardcard to expand it; that went in an ISA
| slot, if I remember correctly. The disk controller might have
| been in an ISA slot, too.
|
| I think that pre-AT era would have constrained DOS <5.0 more
| than the IDE/SATA/SCSI eras.
| tempodox wrote:
| If 640 KiB of RAM was all anybody would ever need, what were they
| going to do with more than two hard disks?
| theamk wrote:
| You can never have too much space.
|
| Plus, as better disks appeared, older disks became much cheaper
| (or even free in some cases). It was pretty simple to collect a
| few of older, smaller, drives and stick them all in one machine
| just to give it more space.
| bombcar wrote:
| People laugh about that, but when you look at when the whole
| thing was designed and came out, and how much it would have
| cost to have a "pimped out" system that pushed the limits (if
| even possible!) it becomes much more reasonable.
|
| _Nobody_ expected this silly machine to be relevant and
| affecting computing 44 years later!
|
| It came with 16KB of RAM! 640KB would have been 40 times as
| much - that's the equivalent of a modern laptop (which comes
| with _checks Apple_ 16GB of RAM) going up to 640GB of RAM.
|
| The original machine had support for two floppies and a tape
| drive - the first hard drives were in the 5MB for $2000 in 1982
| range. That's about $6,700 today.
|
| Even the writings of the day assumed that the IBM PC would last
| "for a time" like all previous machines had, newer ones would
| come out on new chips that were completely different. Nobody
| really expected backwards compatibility and Windows to eat the
| world.
| forinti wrote:
| For the applications that were really important then
| (spreadsheets and word processing) even 64KB would be
| reasonable for most people. With 640KB you could run a
| medium-sized business.
| bombcar wrote:
| I loved the HP200LX just for that reason - it was a hand-
| held 90s palmtop that was a full-fledged 186, with DOS 5.0
| and "multitasking" and about a meg of RAM - and it could
| run ANY of those 80s programs, including a full Lotus 1-2-3
| spreadsheet.
|
| That power - phenomenal, especially in the early Internet
| age.
| mikepurvis wrote:
| Wasn't power management an issue with early portable
| computers? I feel like it wasn't until Windows 95 and
| beyond that machines were properly sleeping in between
| tasks-- before then you were likely to end up just
| spinning the processor in an idle task.
|
| This kind of thing can even be a problem trying to
| virtualize DOS stuff: https://www.os2museum.com/wp/idle-
| dr-dos/
| bombcar wrote:
| That was the other thing - it would run for _ages_ on 2
| AA batteries.
|
| https://en.wikipedia.org/wiki/HP_200LX
|
| 30-40 hours but it worked out to basically "it was always
| good to go".
| rwmj wrote:
| What you say is true, but I'd also like to ask (people in
| general) if you have to design a memory map for MS-DOS that
| doesn't have the 640K limit, _what would you do?_ Your
| constraints are:
|
| - The total address space is 1MB, and that's a CPU
| architectural limit (which is only "broken" many years later,
| and in a rather unsatisfying way).
|
| - You need somewhere to map the RAM, and because of CP/M
| quasi-compatibility, that needs to start at address 0.
|
| - The CPU starts executing code at 1MB minus a few bytes, so
| your system ROM must go right at the top of address space.
|
| - You need memory windows for the system ROM, options ROMs
| and 2x framebuffers.
|
| - Bank switching adds extra complexity and 74xx logic chips
| on a motherboard which is already very busy.
|
| Given these constraints, the 640K limit for RAM, with
| framebuffers and ROMs mapped at 0xA0000, is the only thing
| that makes sense.
| bombcar wrote:
| The 640 limit complaints aren't really about DOS; they're
| about Intel's segmented memory architecture (again, which
| had its reasons and greatly _increased_ the ability of the
| chip at the price-point).
|
| Most people first experienced it long after it was seen as
| a _crippled_ chip, which is not what it originally was.
| bell-cot wrote:
| For those too young to remember that "unsatisfying way" of
| breaking the 1MB limit:
|
| https://en.wikipedia.org/wiki/Expanded_memory#Expanded_Memo
| r...
|
| (And IIR, Bill Gates had plenty of company in denouncing
| EMS while announcing official support for it.)
| rwmj wrote:
| I was actually thinking of the A20 line, but LIM EMS was
| _another_ unsatisfying way!
| https://en.wikipedia.org/wiki/A20_line
| inetknght wrote:
| > _that 's the equivalent of a modern laptop (which comes
| with checks Apple 16GB of RAM) going up to 640GB of RAM_
|
| 640GB of RAM doesn't sound unreasonable to me.
| bombcar wrote:
| Found the Chrome user.
| blueflow wrote:
| > ... was missed for years simply because no one had a PC with
| more than two hard disks.
|
| Thats a hardware limit:
|
| Early mainboards only had a single IDE / parallel ATA port. Each
| port has two pins for drive select, so you had a maximum of two
| addressable drives, the master and slave drive.
|
| With a secondary ATA port you got another set of master/slave,
| pushing the limit to 4 drives.
|
| That's where the "primary master" text comes from that showed up
| on the screen during booting.
| st_goliath wrote:
| > Early mainboards...
|
| ... like in the PC AT, PC XT[1] or the Compaq DeskPro 386[2]
| that the article discusses didn't have those ports _at all_.
|
| Those were instead on ISA expansion cards, just like the floppy
| controller that would often share a card with the UART
| controller for the serial interface.
|
| [1] https://theretroweb.com/motherboards/s/ibm-xt-
| type-5160-64-2...,
|
| [2] https://theretroweb.com/motherboards/s/compaq-
| deskpro-386-20...
| accrual wrote:
| Yes, the earliest mainboards I know of with on-board I/O
| including ATA is around Socket 5, the first mainstream
| Pentium boards. Some slightly older Socket 4 boards (circa
| 1994) have on-board I/O, but they weren't as common.
|
| My 486 and earlier systems have all I/O provided by ISA
| cards, other than the 5-pin DIN keyboard port which was
| standard since the original PC.
| manyturtles wrote:
| IDE was just coming in (in the UK) in 1990. The acronym got
| updated to "AT Attachment" because "Integrated Drive
| Electronics" was generic, and it wasn't as if the older
| drives had no electronics on them. Much later when SATA
| showed up, the name evolved again as ATA became known as
| Parallel ATA to distinguish the two.
|
| Before that, when you installed a hard disk you had to go
| into the BIOS to specify the geometry of the drive. 46 types
| were already defined, to match individual drives on the
| market. "Type 47" allowed -- required -- manually specifying
| the drive geometry in terms of cylinders, heads and sectors.
| So for a short while some traditional MFM or RLL drives would
| be informally classed as Type 47 because their geometry and
| capacity differed from earlier drives.
| alnwlsn wrote:
| Similarly, it always bothered me a little that the floppy disk
| interface was designed for 4 drives, but the PC standard came
| up with the clever hack of putting the twist in the cable, so
| they didn't need to adjust drive jumpers, which also reduced it
| to 2 drives.
|
| On the TRS-80, they just ordered all the drives jumped with all
| 4 positions, then pulled out the other 3 unused pins in the
| connector on the cable.
| bombcar wrote:
| The twist as a "cute" solution that made it mostly plug-and-
| play; the biggest upgrade on some of those older machines was
| adding a second floppy, and the twist made it simple and
| foolproof.
| tracker1 wrote:
| You're jumping ahead a bit... early motherboards didn't have
| drive adapters at all, let alone IDE or PATA. And it wasn't
| really limited to two by the board and expansion slots nearly
| as much as the physical form factor and cost. "Full-height"
| 5.25" drives are double the height of what you think of for say
| a CD drive bay or later floppy drive bays. There were two in
| the XT/AT cases that were common. Hard drives went from full-
| height 5.25 to 3.5" pretty quickly and there weren't many half
| height or otherwise short 5.25" hard drives. There was a "big
| foot" drive that sucked, that I recall though.
|
| Most people I knew with computers prior to 1992 or so either
| booted from floppy or had less than 40mb hard drives. They were
| expensive. By the time I got more into the hardware (1994 or
| so), dual IDE was common (4 devices) and PATA transition was
| pretty seemless. The only reason I'm even aware of the
| difference is I worked at iomega for a while, and the IDE zip
| drive was IDE and not PATA.
|
| Around 2001, I had a motherboard with dual PATA and another
| PATA that was via onboard raid controller. I had 4hdds, a cd
| burner and an ide zip at that time. The drives I had first used
| were the first IBM Deskstar drives... fast, but died very
| prematurely... the second died before I could RMA the first. I
| had switched from OS/2 to Windows 2000 (not ME) around that
| time. Then came SATA, and no more rounding pata cables.
| RHSeeger wrote:
| When we got our first (10M) hard drive for our IBM PC (the
| original IBM PC), we had to buy a second case for it; because
| the power supply in the first one couldn't power it. On the
| positive side, it meant we had somewhere to put the TV we
| were using as a graphics monitor (since the main monitor was
| a green monochrome monitor).
| skopjadurk wrote:
| Built my first pc in 1987. RLL/MFM were the drive choices. I
| had a 32 MB had entering college and it was cheaper than 640
| KB of DRAM DIPs. I upgraded to a 100 MB ide in 1992 for ~$220
| US. But I Was booting from HDD from day 1 in 1987.
| mikeytown2 wrote:
| Sound Cards with IDE ports for CD-ROM drives were definitely a
| thing back then
| Zardoz84 wrote:
| Yeah! I'm trying to get a Sound Blaster 16 with IDE + a VESA
| IDE controller working on a 486DX2@66
| cestith wrote:
| There were also a number of sound cards that had two or three
| ports because a lot of early CD-ROM drives weren't IDE. You'd
| have a Sony, a Panasonic, and something else on your card in
| the early days. IDE on a sound card was an actual improvement.
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