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More than two hard disks in DOS

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Re: More than two hard disks in DOS

#11

Post by st_goliath »

blueflow wrote: post #9

> ... 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" te…

> 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...

Re: More than two hard disks in DOS

#12

Post by rwmj »

pjmlp wrote: post #4
philipstorry wrote: post #2

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…

And expensive, really expensive.

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

Re: More than two hard disks in DOS

#13

Post by accrual »

st_goliath wrote: post #11
blueflow wrote: post #9

> ... 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" te…

> 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-d…

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.

Re: More than two hard disks in DOS

#14

Post by alnwlsn »

blueflow wrote: post #9

> ... 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" te…

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.

Re: More than two hard disks in DOS

#15

Post by bombcar »

alnwlsn wrote: post #14
blueflow wrote: post #9

> ... 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" te…

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.

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.

Re: More than two hard disks in DOS

#16

Post by theamk »

tempodox wrote: post #8

If 640 KiB of RAM was all anybody would ever need, what were they going to do with more than two hard disks?

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.

Re: More than two hard disks in DOS

#17

Post by bombcar »

tempodox wrote: post #8

If 640 KiB of RAM was all anybody would ever need, what were they going to do with more than two hard disks?

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.

Re: More than two hard disks in DOS

#18

Post by forinti »

bombcar wrote: post #17
tempodox wrote: post #8

If 640 KiB of RAM was all anybody would ever need, what were they going to do with more than two hard disks?

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 mode…

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.

Re: More than two hard disks in DOS

#19

Post by bombcar »

forinti wrote: post #18
bombcar wrote: post #17

Earlier quoted context omitted.

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 mode…

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.

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.

Re: More than two hard disks in DOS

#20

Post by mikepurvis »

bombcar wrote: post #19
forinti wrote: post #18

Earlier quoted context omitted.

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.

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.

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/

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