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Learn Something Old Every Day, Part V: Early IBM PS/2 Hard Disks →

Posted on April 29, 2022 by Michal Necasek

Some time ago, I lamented that even though the OS/2 Museum had a good number of disks of the final OS/2 2.0 beta, level 6.304, there wasn’t enough to install the OS, let alone any of the development tools or add-ons (Extended Services, LAN Server).

And now, more or less exactly 30 years after build 6.304 was released (February 1992), an IBM DAP (Developer Assistance Program) CD-ROM turned up with the complete 6.304 disk set, plus Developer’s Toolkit, C Set/2 compiler, Extended Services, LAN Server 2.0 Entry/Advanced, documentation, and a couple of other goodies. IBM also sometimes referred to OS/2 level 6.304 as EEP, or Early Experience Program, and provided a helpful “Product Considerations” booklet.

There was also one surprise: It was possible to install this pre-release of OS/2 2.0 directly from CD-ROM (that was also possible with the Limited Availiability Level 6.177 CD-ROM, but with completely different storage drivers).

As far as I know, OS/2 2.0 was never available on CD-ROM, although IBM shipped OS/2 on CD-ROM with certain PS/2 Ultimedia models. It was only with OS/2 2.1 (1993) that IBM started offering OS/2 on CD-ROM, thought by the time Warp 4 was released (1996), OS/2 was available on CD-ROM only.

When OS/2 6.304 came out in early 1992, CD-ROMs were just starting to ramp up. The trouble was that the market was rather fragmented. There were SCSI CD-ROMs (and IBM sold those), but there were also several proprietary interfaces from Philips, Sony, and others. Even SCSI CD-ROMs weren’t all that standardized before the SCSI MMC (Multi-Media Commands) specification appeared.

The upshot was that even though OS/2 6.304 included CD-ROM support, it was far from certain that a user equipped with a CD-ROM would be able to use it on a non-IBM machine. Even with a “standard” SCSI CD-ROM, the user might need to supply a driver for the SCSI HBA (IBM only shipped drivers for the most common Adaptec 154x/174x HBAs with OS/2, plus a couple of Future Domain models), and that wasn’t enough either; a separate CD-ROM support driver was required, and CDROM.SYS shipped with OS/2 only supported IBM and Toshiba SCSI CD-ROMs.

Sometime in mid-1992, IBM provided a “generic” CDROM_G.SYS driver which did not support audio functionality but worked with more or less all SCSI CD-ROMs. For OS/2 2.1, IBM reworked the CD-ROM support and provided several vendor-specific filter drivers.

OS/2 6.304 from CD-ROM

It’s clear that the CD-ROM install of OS/2 6.304 was a bit of a hack. It was very similar to installing OS/2 from a hard disk partition, but with some caveats. The installation was not automatic and required a bit if hand-holding. IBM documented the necessary steps reasonably well.

First of all, to install from CD-ROM, the installation partition on hard disk had to be created first. The reason was that if the partition didn’t exist, the CD-ROM would be mapped as drive C:, confusing the installer. The partition did not need to be marked as bootable or installable, it just needed to exist in order to reserve the C: drive letter. When installing from floppies, there was no such restriction.

IBM provided images of the bootable Installation diskette plus Diskette 1; the latter had to be modified by the user. At minimum, CONFIG.SYS had to be edited to point at the right drive letter for the CD-ROM. The user may have also needed to supply a driver for a SCSI HBA and/or for a proprietary controller that the CD-ROM was attached to. These drivers needed to be copied onto Diskette 1 and CONFIG.SYS edited appropriately.

To test the installation, I used a VirtualBox VM with BusLogic SCSI emulation and BTSCSI.ADD driver dated 04/07/1994 acquired from the old Mylex FTP.

IBM probably only really tested the CD-ROM installation on IBM PS/2 machines. On non-IBM systems, the CD-ROM installation breaks down in a rather non-obvious way when the OS is first booted from hard disk.

The installer copies any additional drivers from Diskette 1 to hard disk, but it does not propagate the related CONFIG.SYS statements to the CONFIG.SYS on the hard disk. That leads to a rather interesting result: OS/2 will likely be able to boot from hard disk thanks to the generic IBMINT13.I13 BIOS disk fallback driver, but the CD-ROM won’t be accessible and the installer will fail. This is what the failure looks like:

It is difficult for the user to understand why the installation failed, and the log file is only slightly more helpful:

The WIN.INI and SYSTEM.INI files can’t be updated because they’re not there. And they’re not there because they were never copied. Only the installer is a bit optimistic and does not complain that it wasn’t able to copy anything at all, it just quietly goes to the next step and then fails.

The remedy is to not let OS/2 boot from hard disk right away but instead boot from the two floppies again, and then edit CONFIG.SYS on the hard disk to add the statements necessary for the CD-ROM to be accessible. That’s not made any easier by the fact that there’s no text-mode editor shipped with OS/2 2.0. Borrowing TEDIT.EXE from OS/2 Warp is one way to get around that problem.

In my case, it was necessary to re-add two lines to CONFIG.SYS:

BASEDEV=BTSCSI.ADD
BASEDEV=OS2SCSI.DMD

For whatever reason, the installer did preserve the lines with CDFS.IFS and CDROM_G.SYS, but lost BTSCSI.ADD and OS2SCSI.DMD.

Once CONFIG.SYS is fixed, the second phase of the install copies files to hard disk, and sets up Win-OS/2, but then fails again. I have not been able to figure out why. Depending on whether the user retries or not, the installer may crash:

I believe the installer should offer installing printer drivers at that point but it doesn’t quite get so far.

Interestingly, if the system is rebooted, it appears to be fully installed, with nothing obviously missing. The only issue is that CD-ROM support is again gone from CONFIG.SYS. That might be because the installer crashed, or it might be because the CD-ROM install path is very rough around the edges and unfinished. Once again, manually editing CONFIG.SYS can fix that.

All in all, the CD-ROM based installation is hardly worth it. It’s not surprising that it wasn’t well tested, especially on non-IBM systems. Nevertheless, it does more or less work:

The 6.304 pre-release is not very visibly different from OS/2 2.0 GA. That is hardly surprising, given that it’s just a few weeks older. But it really is 6.304:

The standard floppy-based installation of 6.304 works better, and requires a lot less hand-holding.

In any case, it’s great to have the final OS/2 2.0 pre-release, even if it took 30 years. There’s a decent chance that older OS/2 2.0 betas are still hiding out there somewhere.

This entry was posted in CD-ROM, IBM, OS/2, PC history, Pre-release. Bookmark the permalink.

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Learn Something Old Every Day, Part V: Early IBM PS/2 Hard Disks →

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