> ... 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.
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.
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.
... 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.
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!
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.
I had 3+ fixed disks somewhere around 1997, but that was on a Mac (so built-in SCSI), and the drives were all hand-me-downs that I got for free, that I could just plug and play to add a few more hundred megs of storage.
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.
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.
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.
blueflow|6 months ago
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.
tracker1|6 months ago
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.
alnwlsn|6 months ago
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.
st_goliath|6 months ago
... 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...
burnt-resistor|6 months ago
P-ATA IDE didn't arrive until the late 80's.
philipstorry|6 months ago
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!
dardeaup|6 months ago
Telemakhos|6 months ago
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.
jmclnx|6 months ago
Not long afterwards I ended up on Coherent OS, fun times.
kalleboo|6 months ago
pjmlp|6 months ago
tempodox|6 months ago
bombcar|6 months ago
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.
theamk|6 months ago
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.
mikeytown2|6 months ago
cestith|6 months ago
Zardoz84|6 months ago