IBM ThinkPad Power Series 850

In the mid-1990s, IBM and Motorola unsuccessfully tried to create a new personal computer platform built around PowerPC RISC processors. Apple was initially a member of the alliance called AIM (Apple/IBM/Motorola) and used PowerPC processors in its own Macintosh systems for over 10 years.

PowerPC Logo

IBM’s line of machines was called Personal Power Series (PPS) and included several desktop models as well as portables sold under the ThinkPad brand. There was a very close link between the PPS machines and specific RS/6000 models.

ThinkPad Power Series History

Sometime in 1994, IBM started working on a prototype mobile system named Woodfield and designated as type 6020. Very little is known about this system; it was never officially announced or sold. On June 19, 1995, IBM announced the ThinkPad 850 and 820 (announcement letters 195-178 and 195-179, respectively) with a planned availability date of July 24, 1995. The ThinkPad 820 designation was type 6040, code name Wiltwick; the 850 was type 6042, code name Woodfield Prime.

ThinkPad 850

The ThinkPads 820/850 were to be available with no software or with preloaded Windows NT 3.51 or AIX 4.1.3. OS/2 was to come at some unspecified later date, and Solaris 2.5.1 support was announced in February 1996.

The ThinkPad 850 type 6042 came with 16 or 32 MB RAM, 540 or 810 MB hard disk, and 640×480 or 800×600 TFT display.

ThinkPad 850 Firmware Logo

After only a few months, on February 20, 1996 (announcement letter 196-028), the Power Series ThinkPads were re-announced under different type designations. The 820 was now type 7247 and 850 turned into 7249, perhaps to better fit into the RS/6000 numbering scheme. The hardware was not changed, but the initial configurations were. The systems now all came with 32MB RAM and 810MB disk, and all 850s used 800×600 panels.

ThinkPad Type Designation

At the same time, the desktop Power Series 830/850 models were withdrawn, with RS/6000 machines listed as replacements. There was no longer any mention of OS/2 either, but AIX, Windows NT, and Solaris were offered as ThinkPad Power Series operating systems.

On October 8, 1996, the withdrawal of the ThinkPad Power Series systems was announced, less than 18 months since the initial product announcement. The systems were replaced by the RS/6000 Notebook 860 (designated 7249-860), which was essentially a ThinkPad 850 with faster 166MHz 603e CPU, a larger 1024×768 display, and an upgraded graphics chip (S3 Aurora64+ instead of WD90C24). The 860 no longer used the Power Series or ThinkPad branding.

Power Series Logo

The ThinkPad Power Series systems were clearly not successful. However, this was not necessarily due to any deficiency in the machines themselves. The entire PowerPC initiative fizzled and even if the PowerPC ThinkPads were brilliantly designed, solidly built, and cheaply sold (the latter certainly wasn’t the case), there wasn’t any real market for them. However, that does not makes these systems any less interesting.

ThinkPad 850/820 Hardware

The ThinkPad 850 was a PReP (PowerPC Reference Platform) machine, technically quite similar to the desktop Power Series machines but with a few key differences. The heart of the system was a 100MHz 32-bit PowerPC 603e CPU, a low-power member of the PowerPC family (only about 6W power consumption at full speed). In 1995, this was quite a lot of power in a mobile system, especially in terms of floating-point performance.

The ThinkPad 820 used a 32-bit memory subsystem, while the 850 utilized a 64-bit data path much like the contemporary Pentium processors (and therefore also required memory upgrade modules to be installed in pairs). The base system came with 16 or 32 MB RAM and was upgradable to 96MB (48MB for the ThinkPad 820). 96MB RAM in a laptop was a massive amount in 1995.

The 850 used IC DRAM modules rather than standard SIMMs or DIMMs. This makes upgrading memory in these systems somewhat tricky.

While the Power Series desktops used a “Dakota” memory controller, the equivalent part on the ThinkPads was called “Idaho”. The Dakota is fairly well documented in the original PReP specification; the Idaho much less so. The ThinkPads also used a power management controller called “Carrera” about which very little is known. Another difference between desktops and laptops was that the ThinkPads included a PCMCIA controller and two PC Card slots.

Another difference was graphics. The ThinkPads had a built in Western Digital WD90C24A2 VGA LCD controller with 1MB VRAM. This chip drove an 800×600 TFT display (640×480 on some models). The ThinkPad 850 additionally included a video capture chip; this is an ASCII Corporation V7310 VGA overlay—unfortunately, no documentation for chip appears to be available. A snap-on camera was available for the 850, an early precursor of modern built-in cameras (we’re talking 1995!).

Audio was taken care of by a Crystal Semiconductor CS4231 chip. This chip was compatible with Microsoft’s Windows Sound System hardware and did not provide any other features. The desktop Power Series 830/850 machines used CS4232 chips which additionally sported Sound Blaster and AdLib (OPL3) compatibility. The ThinkPad sported built-in stereo speakers and a microphone as well as headphone and line in jacks.

Storage was unusual to say the least. The ThinkPad 850 used the same NCR 53C810 SCSI host adapter as the desktop Power Series 440 machine (the 830/850 desktops on the other hand used IDE storage). The NCR 810 was one of the earliest PCI SCSI controllers available, which was no doubt one of the reasons why IBM chose it for the PowerPC prototypes in 1993-1994.

Since the Power Series ThinkPads were designed as high-end systems, they came with a built-in (but swappable) CD-ROM, while a floppy drive had to be attached externally using a proprietary IBM cable (USB didn’t quite exist back then) and a drive enclosure that fit standard ThinkPad floppy drives. The hard disk was unusual in that it supported a soft-selectable SCSI ID, while the CD-ROM utilized classic jumpers. Another slightly unusual characteristic of the CD-ROM was that it could emulate 512-byte sectors, a feature required for bootable PReP CDs.

ThinkPad 850 internals The CD-ROM and hard disk could be pulled out after popping up the keyboard. Once the disk and CD-ROM were removed, the IC DRAM modules became accessible.

ThinkPad 850 sans disk and CD-ROM

Overall, the ThinkPad hardware was very PC-like—the PowerPC designation was quite appropriate. The memory, disks, floppy drive, serial and parallel ports, PCMCIA controller, even the interrupt controller and DMA controller were just like on Intel ThinkPads. The SCSI disk and CD-ROM were rather exotic, but not something that would have any trouble working in a PC. It is worth noting that although the ThinkPad had no ISA slots, it did have an ISA bus with several devices attached and used an Intel SB82378ZB PCI-to-ISA bridge.

The system as a whole shared many components with IBM’s contemporary ThinkPads, especially models 750 and 755. Only the CPU was a PowerPC instead of a 486 or a Pentium, and the system could operate in big endian mode.

 ThinkPad 850 Firmware

The firmware in the ThinkPad 850 was similar to the desktop Power Series firmware but more self-contained. A mouse driven, graphical Easy Setup was the only interface normally visible to the user. Instead of requiring a SMS (System Management Services) diskette to make changes (echoes of a PS/2 reference disk or a PC/AT setup floppy), everything was built into the firmware. No doubt this was a consequence of the fact that the ThinkPads did not come with a built-in floppy drive.

ThinkPad 850 Easy Setup

Naturally the firmware conformed to the PReP specification. It was relatively simplistic and differed from both an x86 BIOS and Open Firmware in that there were no run-time services whatsoever. The firmware loaded the OS (or more likely its boot loader) from a storage medium, built “residual data” describing the system’s hardware, and started executing the OS bootstrap code. From that point on, the OS had to take over and fully control the hardware.

Unlike a typical PC BIOS, the Power Series firmware offered very few configuration options. Apart from boot priority options, there was almost nothing to configure. On the other hand, the firmware included a fairly extensive set of hardware tests.

ThinkPad 850 Firmware Tests

There was a semi-secret firmware console which could be entered by typing “eatabug” on the Easy Setup welcome screen. The console resembled DOS (and also an EFI shell); it could access FAT-formatted floppies and hard disk partitions, as well as ISO-9660 CD-ROMs. It could execute external files and included a number of built-in commands to dump memory, read and write files, etc. There was also a simple debugger, although the disassembler had been removed from the ThinkPad firmware which made it rather less useful. On some SMS disks there was even a basic text editor.

ThinkPad 850 Firmware Console

The Power Series firmware was very modular, with drivers and executables in separate files. It was also extensible and hardware could ship with device-specific setup and diagnostic firmware modules. Having similarly well designed firmware on PCs in 1995 would have been a boon, but alas, it was not to be.

The OS/2 Museum ThinkPad 850 Unit

The ThinkPad Power Series 850 which is now part of the OS/2 Museum collection is a second generation unit, type 7249-851. It was most likely manufactured in mid-1996, although it is difficult to ascertain which parts are original and which parts may have been replaced at some point.

ThinkPad 850 Top

The system is fully stocked with 96 MB RAM and a 1.2GB hard disk. The 1996 list price would have been $12,399 plus a 64MB memory upgrade (consisting of two 32MB IC DRAM memory modules) at $6,174, adding up to a truly grand total of $18,573. Whether anyone ever paid such an exorbitant price for the system is unknown.

The laptop’s shell is quite battered—the photos clearly show this—and almost all the hinged lids (battery, PCMCIA slots, rear ports) are missing. The battery is dead, though anything else would have been a real surprise. On the other hand, the inside of the system is in very good condition. The display has no dead pixels and the keyboard has almost zero wear. The only annoying issue is that the left trackpad button only functions intermittently; this does not appear to be a mechanical problem but simply aging contacts or traces. An external PS/2 mouse handily solves this.

ThinkPad 850

It almost looks like someone bought the system, used it very little, and then threw it into a bin with old parts where it languished for years, until someone realized that it’s actually still worth something.

All attempts to track down a hardware maintenance manual (S30H-2388) or a user guide failed. Luckily the system works well enough that this isn’t a critical problem, and the ThinkPad 7xx series HMM shed some light on the technique of dismantling the keyboard.

ThinkPad 850 Keyboard

The unit came with version 1.01 of the firmware. An image of the original 1.0 firmware is nowhere to be found; a later version does not appear to exist.

It was necessary to purchase an external floppy drive (Windows NT or Solaris cannot be installed without one), but luckily this wasn’t difficult as the Intel-based mid-1990s ThinkPads used exactly the same drives.

All in all, the ThinkPad 850 is a very interesting part of the history of computing, a rare RISC laptop with many of the trimmings of modern portables.

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38 Responses to IBM ThinkPad Power Series 850

  1. Richard Wells says:

    Can you provide a subjective review as to how it feels in use? For example, does it get hot when under load?

  2. Michal Necasek says:

    Disclaimer: the following is not based on heavy daily use.

    The unit feels more brick-like than modern laptops, it’s thicker and heavier, but certainly a lap-top. It’s well built, despite the obvious wear of the outer shell.

    The laptop does get quite warm on the bottom, but not so warm that I’d have to get it off my lap. Definitely not as hot as modern laptops. The top gets barely warm. There is no fan, so the system is pretty quiet. The CD-ROM is loud when it seeks, but that’s not exactly typical activity. Replacing the hard disk with a CF card would probably make the system extremely quiet. There’s also the option of hooking up external SCSI devices.

    The display brightness and contrast is lower than on modern systems. I don’t know how much of it is due to its age and how much is the technology used. The image quality is by no means bad though! The viewing angle is quite decent and there is very little ghosting (so little that I had to look for it to see it). The external VGA signal quality is surprisingly good, better than two different contemporary desktop S3 cards I tested (with S3 SDAC and Bt485 DAC, respectively).

    The keyboard is basically desktop sized, very pleasant to work with. The trackpad works quite well (except for the slightly flaky left button which I’m sure is age related, and which tends to work better after it “warms up” a bit).

    The pop-up keyboard is super easy to flip out and all user-serviceable parts are very easily accessible. No tools are needed to swap out the hard disk, CD-ROM, or memory modules (not to mention battery). Since the battery is dead, I have no idea about battery life.

    I’ve not really put the built-in speakers to the test, but they can certainly make some noise and are very nice to have in a laptop this old. I do wish there was a built-in Ethernet controller but that’s what the PCMCIA slots are meant for.

    Under NT 4.0 and Solaris 2.5.1 the laptop feels reasonably zippy and is pleasant to work with. The hard disk is no speed demon but the CPU is decently fast and the 96 megs of memory help a lot.

  3. Michal Necasek says:

    Update: Since I have Solaris installed on the ThinkPad 850 right now, I couldn’t easily play an audio CD to test the speakers. This prompted me to build WorkMan (an old *nix CD player) which allowed me to play CDs through the internal speakers. The speakers are quite decent, the sound is of course a bit tinny compared to my home stereo but I’d say very good for a 1995 laptop.

  4. Peter Yoo says:

    oh! great. read your thread already. good. thankyou.

    5 years before me know 860. after want buy.
    sometime look ebay but cannot find this laptop.

    you ok then, where buy solution give to me.
    (my english very ugly. sorry)
    i want operation os/2 on thinkpad 8xx.
    (im using ecomstation 2.1)

  5. Michal Necasek says:

    If you really want a ThinkPad 8xx, you can try . I have no idea how much they they charge.

    OS/2 is definitely not a good OS to put on one of these. It’s slow, unstable, and simply too unfinished. Solaris or NT works far better. Probably AIX and Linux do as well.

  6. Peter Yoo says:

    oh. me know that’s web site. but really expansive.
    talk then thinkpad 860 is 10,000$ more. can’t buy.

    thank you for your reply.

  7. Michal Necasek says:

    I guess they’re charging new prices… too bad!

  8. Peter Yoo says:

    i think too. but how can? hahaha.
    thank you 😀

  9. Uber-cool and very insightful…don’t suppose you have something similar on the Power Series 600 do you? Even IBM seem to struggle when it comes to that particular PowerPC based box =:)

  10. Michal Necasek says:

    So do I. To be honest, I have never heard of Power Series 600 until now. There’s extremely little information about it and it doesn’t look like it was a product that IBM ever sold (and it’s not like the other Power Series sold that much). I don’t suppose you have one of those? 🙂

  11. Amazingly I do…which is why I was hoping to find something out about it as there’s is precious little out there – even contacted IBM and they kinda shrugged their shoulders and said ‘we’ve never heard of it’ =:(

  12. Michal Necasek says:

    I’m not surprised. I’ve gone through a lot of IBM materials and have never seen a hint of Power Series 600. The 830/850 desktops and 820/850 portables are comparatively well documented, and even the Power Series 440 which I believe wasn’t really sold is mentioned enough times.

    Do you have some type number(s) for the PS 600?

  13. According to the case it’s a Power Series 600 (model No. 6030) and, having torn it apart, it’s running a PowerPC 603 CPU, God knows what RAM (there’s nothing like DIMMs or SIMMs in there), an S3 graphics card (with who-knows-what connector as I’ve never seen anything like it), 6xPCMCIA slots (4xexternal, 2xinternal), SCSI HD and CD-ROM, and a 2.88Mb floppy drive.

    I’ll be honest, it’s got me scratching my head big time

  14. Michal Necasek says:

    This is definitely prototype hardware. If it had been sold, there would be some trace in IBM announcements etc. (like the Power Series 8xx). What I can tell you right now is that if you look at the PowerPC Reference Platform Specification, version 1.1 (PReP), you’ll find Appendix A.2 describing an “Energy-Managed Workstation” that remarkably closely matches what you’ve got there.

    And if I’m right, those “internal PCMCIA slots” are in fact IC DRAM slots for memory expansion, the same kind used in ThinkPads (both PowerPC and x86). Not that hard to find actually.

    Does your box have any software on it at all?

  15. Ah…I had half a hope that this might be ‘prototype’ but didn’t want to make any assumptions. It might explain why this thing just doesn’t appear anywhere and I am eternally grateful for the info =:)

    No software on it that I can tell and, just to make things even more ‘awkward’, the output graphics are corrupted. You can make out the IBM logo and it boots to ‘something’ but it appears to be an ‘insert disk’ animation. *While* it’s getting the ‘insert disk’ animation it displays something remarkably similar to some of the screens that you’ve posted. I *could* pop the drive in another machine and have a look but I don’t hold out much hope of a) it being read and b) there being anything on it.

    As for the ‘internal PCMCIA’ slots then, as there doesn’t seem to be any other sort of memory expansion, then it would make sense and gives me something to go away and investigate.

  16. Gremar says:

    I worked in IBM Thinkpad development in the late 90’s writing software tools that were shipped along the systems. One day they closed our function and took it to USA. After the ‘clearance’ (what’ll go, what’ll stay and what’s thrown), we were let go through all the ‘rubbish’ in the large plastic trolleys of things to throw in case we were interested on ‘keeping something’. I took ‘few things’, and one of them is a Thinkpad with only one marking on the front: ‘Power Series 800’. Its Type is 6020-560 and it includes a serial number starting with 97 (our manufacturing code), so this indicate that IBM was at least manufacturing the Type 620 in UK at some point. Whatever they didn’t marketed or sold was a surprise to me as this system was working with AIX 4 in it. But unfortunately I do not have a power supply and battery run out.

  17. Michal Necasek says:

    Wow, you’re the first person I know of who has a 6020. From what I know, it was the “prototype” PowerPC laptop, codename Woodfield. I don’t think the 6020 was ever marketed as a product, but it was almost certainly given to developers, like the Power Series 440.

    Manufactured in UK – was that Greenock like other UK-made ThinkPads? And does it need some custom power supply or is it one of the same types that the 700 series ThinkPads used? IIRC the ThinkPad 850 power supply isn’t special, although the batteries are.

  18. Gremar says:

    Yeah it was Greenock. Our Thinkpads had manufacturing codes 97- and 99-, although might be others I do not know of. I am also surprised about this sudden discovery that I have a prototype, I just thought that a Power Thinkpad was a cool thing to have. It is obvious to me now that whoever did the clearance never suspected it or just didn’t care. What you say that they gave it to developers make sense, because it was in my department’s bin, and we wrote tools and drivers for them. I sent you the photos you requested. 🙂

  19. Antoni Sawicki says:

    FYI I have a spare power supply and a battery for PowerPC thinkpad if you are interested.

  20. Mike Senior says:

    I have an IBM Thinkpad Power Series 850 User Guide

    Part Number 79H3648

  21. Shartley says:

    Just came across this discussion while surfing for accessories for my 850. If anyone is interested in more info, I have an IBM Thinkpad 850 still in the box with all of the accessories, software and documentation. Pictures are at the following link:

  22. Shartley says:

    For some reason the link did not show up in my post. Here it is:

  23. Michal Necasek says:

    Wow, that’s quite something!

    I’d definitely be interested in images of any CDs/floppies that came with the system. And an image of the original hard disk would be terrific, too.

  24. Shartley says:

    Absolutely! I will take some pics over the holiday and post them to the Photobucket site. Will let you know when they are there.

  25. Michal Necasek says:

    Ah sorry, I wasn’t clear… I meant ISO images of CDs, although photos/scans would be nice too 🙂 I think the chance of finding the actual CDs for my ThinkPad 850 is pretty much nil.

  26. Shartley says:

    In the back of my mind I was actually thinking “He wants actual disk images” as I was typing! I know these things are impossible to find. Many times when you find a working Thinkpad PPC the OS has already been installed and password protected. Without the appropriate, installable version of AIX for this machine it is a nice looking paperweight in that case.

    I will make .iso images of the CDs that came in the box. No floppies were included. Not sure if I will be able to make an image of the HD. I believe AIX uses a JFS file system. I have the cables to connect the SCSI HD to my Mac but, not sure if it would mount for me to make an image. I’ll give it a try. Will at least get the .iso images to you. Let me know if you have an FTP location.


  27. Michal Necasek says:

    My 850 came with NT 4 installed, which is not a bad OS for the hardware as such, but it’s not as historically interesting as others. ISOs would be terrific.

    If you can hook up the hard drive to a Mac (or anything really), you should be able to create a raw disk image with ‘dd’. The filesystem on the drive does not matter and more or less any OS will be able to copy such image onto a TP 850 hard disk again. See e-mail re FTP.

  28. Ian Smith says:

    Hi, I have a Thinkpad Power Series 850 and have been told the reason it doesn’t go all the way with boot-up is due to the firmware battery being dead. Does anyone know is this easy to replace, and is it likely a good laptop repair shop could do it?

  29. Michal Necasek says:

    Do you have the exact error number/message?

    The backup battery is easy to replace, finding a new one is the tricky part. If I recall correctly, the battery is under the CD-ROM. This may also help.

  30. Well, here’s another report of a Type 6020. This one came with the 850 video rig, but it’s a Type 6020 on the bottom. Serial number starts with 97-. Like Gremar’s, it also says “Power Series 800” on the front. However, there are also little blue “TP850-” stickers all over it, which I can’t tell if they were added by the previous owner(s) or came from IBM that way.

  31. I was an IBM Global Services employee in this vicinity, and I was able to find a supply of the 860s that the West German army either didn’t take delivery of after order, or did accept but then sent back. I used one of them as my personal laptop over a year.

    AIX 4.1.3 was the last supported AIX platform for the 860, but 4.1.4 worked on an upgrade. I got 4.2.1 working, without X support. We even got PCMCIA modems and IBM modem dial-in working.

    However, a lack of support just doomed the little troopers. When 4.3 came out, I had to move on to a Linux build on Intel.

    I still miss these little 603e boxes.

  32. Jeremy says:

    You can HQ rip the startup screen but not the startup sound? Now that’s just Half-Baked 3. sigh

  33. dosman says:

    Ha, came here looking for info on these machines after seeing a Hackaday article on a Power9 mainboard. Like Kentucky Packrat, I was a IBM Global Services guy. The RS/6000 TopGuns traded the little 820/850’s around as personal dev/test machines loaded with AIX 4.1 even until the mid-2000’s. I was lucky enough to have one for about the last year I was there. Rumor had it that some guys had MacOS and NT running on them too, but AIX was the real reason to have one in our area. I think I had a cdrom with mine but no floppy. I had other AIX machines at home, but having a portable AIX system was pretty cool.

    For folks looking for extinct IBM documentation, occasionally you can find old sets of IBM CD’s on Ebay that say “MoST” on them (usually a single CD-sized sleeve with as many as 20 or more CD’s). This was IBM’s field documentation that SSR’s/CE’s carried around with them before ubiquitous high speed internet and WiFi existed. As far as I could tell, the complete CD set contained all documentation for all equipment going as far back as mechanical punch card gear. The problem is that it uses a Lotus Notes database to index all the data which is completely separate and only available internally. Even though the CD’s were roughly group by equipment type, it would still be quite a job to manually index them. I figure some day it will happen though.

  34. RetroRow says:

    So I have had an 850 since the late 90’s when I was working for a leasing company and this came in off lease. It sat on the weird item shelf for about 8 months before I got the boss to sell it to me for $100. It had AIX 4.1.3 at that point.

    Like others I received it without knowing the password, my solution to that was to format an external SCSI drive and then upgrade to 4.1.5 onto the external, after pointing the installer to onboard 1.2g drive for the qualified upgrade.

    I never got around to upgrading the OS on the internal 1.2G because it was so tiny. I once found a loose 1.2G internal for close to $600. IBM only made 2.5″ form factor SCSI drives for these units.

    4.1.5 is the last Version of AIX that supports the G10 Graphics in the 850(851). You could if you were a masochist install 4.2. but you would only have command line. which is a total waste of a cool and surprisingly bright TFT.

    I’ve only seen pictures of the camera. If the camera is installed, the laptop looses the distinctive step front edge and the speakers are covered making the shape more consistent with modern laptops. If you pull forward and up on the top edge of the center of the screen you pop off a cover exposing the 5 contacts for the camera. I theorized, but never verified that 2 were power and 3 were composite or a S-video bodge to have a shared ground on the composite/intensity channels.

    The 860 doesn’t have the G10 (or the cool graphics options like the camera) and I think Support was dropped for that after AIX 4.3.

    I have all of the doors except the rear door device door(I had it originally but its been lost in the last 25 years), an External Floppy Drive, I upgraded it to 96M of RAM have the 1.2G drive as I mentioned.

    I Still have the 4.1.5 Upgrade CD if that isn’t floating around the internet at this point. As I recall awas a stock AIX 4.1.5 Install, nothing special for the PPC.

    The one thing I don’t see many people mention is that there is a side interlock to keep the PCMCIA cards in their slots. To take the cards out with that in place you need to lift the keyboard and take out a small L shaped piece of metal. Then you can press the card slot button to fully eject the drive. There is also both a Kensington Lock slot on the rear and an extendable cable lock on the front right (opposite) corner.

  35. RetroTP says:

    Hi there!

    How do you boot AIX 4.1 into single-user mode on the ThinkPad 850?


  36. Michal Necasek says:

    I am sorry to say that I have no idea. And I don’t have any AIX documentation on hand.

  37. Harrison says:

    did PReP really need 512B emulation for CD booting? I know Sun systems required this but why on earth would they mandate this for PReP, given how short-sided it is.

  38. Michal Necasek says:

    It’s not clear to me that it did. The PReP spec says that sizes are specified in terms of 512-byte blocks, but it also says that that’s the case even if the physical sector size is different.

    Windows NT and Solaris both needed a boot floppy. OS/2 and I believe AIX did not.

    All that said… it’s pretty trivial for CD-ROM firmware to pretend that sectors are 512 bytes. The bigger problem is differing software expectations.

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