OS/2 Warp installation pitfalls

Posted on November 9, 2011 by Michal Necasek

Recently I had an opportunity to install and update various versions of OS/2 (Warp 3 and later) in virtual machines. In the process I ran into several subtle and not so subtle issues which may be worth recording, complete with fixes/workarounds where applicable.

  • When installing OS/2 Warp Connect or Warp Server from CD, the installer may not correctly select the CD-ROM type. It must be manually set to “Unlisted IDE CD-ROM” (or probably any other IDE CD-ROM type), otherwise the networking install phase will fail with very cryptic errors. Continue reading →
Posted in OS/2, Virtualization | 12 Comments

Is it so hard to document things?

Posted on October 23, 2011 by Michal Necasek

A few weeks ago I spent a bit of time debugging a program which mysteriously failed under DOS 3.3, although it worked without any apparent problem on DOS 4.0 and later, and there was no indication that it required anything later than DOS 3.1 or so.

The problem turned out to be related to INT 21h, function 6300h, a curiously underdocumented DOS API. The call was first implemented in the Far East versions of MS-DOS 2.25 and returned a table of DBCS lead bytes. That is crucial information for software running on DBCS systems, required for correctly parsing pathnames etc. The RBIL also documents the call for Far East versions of DOS 3.2 and later. So what’s the problem? Continue reading →

Posted in DOS | 66 Comments

Running 1-2-3 R3 in a VM

Posted on October 22, 2011 by Michal Necasek

I recently tried to install the infamous Lotus 1-2-3 Release 3 from 1989 in a VM. The program disks included both DOS and OS/2 executables, and both were failing. The DOS version stopped with “Cannot initialize system driver” immediately after showing the splash screen, while the OS/2 version failed with the message “Error loading driver file LTSNW” at about the same point. Google was of no help whatsoever, as often happens with software that old. Continue reading →

Posted in DOS, PC history, VirtualBox | 3 Comments

Need for Speed SE video glitch

Posted on October 16, 2011 by Michal Necasek

When attempting to play the classic racing game Need for Speed SE in a virtualized environment (VirtualBox), I was dismayed to discover that all the in-game videos were completely garbled. Curiously, the introductory video played when the game is first launched looked fine, even though there was no reason to think it should be any different from the in-game videos.

Continue reading →

Posted in DOS, VirtualBox | 7 Comments

WordStar needs address wraparound?

Posted on September 24, 2011 by Michal Necasek

The CP/M compatible interface in DOS was initially documented, later forgotten, and then re-discovered every once in a while.

In 1989, John Switzer described parts of the CALL 5 system call interface mechanism in a slightly hysterical article as a “back door” into DOS and called it a security risk, despite the fact that it was a compatibility interface very deliberately maintained in every version of DOS. However, the article correctly pointed out that the CALL 5 interface bypassed INT 21h hooks. In theory, that could have been used for nefarious purposes; then again, worrying about that on the DOS platform was like being gravely concerned that cold wind could get in through a small crack in the window in a house without a roof. DOS simply wasn’t a secure foundation and patching a tiny hole couldn’t fix the fact that any program running on DOS effectively owned the entire system. Continue reading →

Posted in DOS, PC architecture, WordStar | 11 Comments

Who needs the address wraparound, anyway?

Posted on September 13, 2011 by Michal Necasek

The infamous A20 gate is well known and documented in hair-raising detail. What’s much less well documented is the real purpose of the A20 gate, that is, who actually needs the 8086 address wrap-around to be emulated in the first place.

There is precious little information on that topic. But as it turns out, all versions of DOS, including the OS/2 DOS box and NTVDM in Windows NT, implement a CP/M-like system call interface which cannot work without address wrap-around being emulated one way or another. In other words, any DOS application may in fact need the wrap-around, without necessarily being even aware of the fact. The key is the so-called ‘CALL 5’ compatibility interface, invoked by a near call to the offset 5 of the PSP (Program Segment Prefix). This interface was intended for COM programs, but will work as long the CS register points to the PSP regardless of the program type. So what’s at offset 5 of the PSP? Continue reading →

Posted in DOS, PC architecture | 4 Comments

IBM DOS 5.0 QBASIC hangs on non-IBM systems

Posted on September 11, 2011 by Michal Necasek

Much like its predecessors, IBM DOS 5.0 has no trouble running on clone systems, as long as they’re sufficiently compatible. That includes virtual machines. However, the QBASIC.EXE (and consequently EDIT.COM) program dated May 9, 1991 consistently hangs on any non-IBM system. Why is that?

Analysis shows that the key is the presence (or absence) of ROM BASIC, which was built into the ROM of all IBM PC systems (including PS/2) from the very first PCs until approximately 1991, sometime after IBM DOS 5.0 was released. But why does QBASIC care when it’s supposed to replace the ROM BASIC anyway? Continue reading →

Posted in BIOS, DOS, PC history | 20 Comments

Hang with early DOS boot sector

Posted on September 3, 2011 by Michal Necasek

While installing various versions of DOS for the DOS history series of articles, I was faced with a mysterious problem: Some versions of DOS would hang right away when booting from fixed disk, but not from floppy. I already knew that DOS 4.x is very sensitive to BIOS stack usage; if a BIOS needs more than 100 bytes or so of stack to process a disk read request, it will fail to boot DOS 4.x from fixed disk, even though the same DOS 4.x can access the same disk just fine when booted from floppy.

However, the hangs I was observing were happening with DOS 2.x and 3.x, and those do not have such tight stack usage requirements. I quickly realized that the problem is caused by a bug in the DOS boot sector: the boot sector code tries to optimize the loading of IBMBIO.COM and attempts to read a whole disk track at a time. That sounds like a good idea, but it’s not. Continue reading →

Posted in DOS | 32 Comments

Happy 30th Birthday!

Posted on August 13, 2011 by Michal Necasek

In honor of the thirtieth anniversary of the IBM Personal Computer, the OS/2 museum started a new series of articles, this time dealing with the history of DOS—the predecessor of OS/2 and the first OS developed by Microsoft in cooperation with IBM. The first two installments deal with the prehistory of DOS and with the DOS 1.x releases. As usual, VirtualBox was quite helpful for supplying screenshots of vintage software.

Posted in DOS, PC history | Leave a comment

The Danger of Knowing Too Much

Posted on August 3, 2011 by Michal Necasek

A few days ago I had to look a little closer at Microsoft’s KEYB.COM because it was misbehaving in a virtualized environment. As a reminder for those readers who perhaps forgot, KEYB.COM was the DOS keyboard “driver” with support for international keyboard layouts. The MS-DOS version of KEYB.COM was incorrectly detecting the keyboard type (thought an 84-key variant was attached, when it was a 101/102-key of course), but IBM’s KEYB.COM from PC DOS 7 had no problem, and the FreeDOS version likewise worked fine. What I found in KEYB.COM was a little surprising.

The authors of KEYB.COM clearly had a lot of  inside knowledge about PC hardware. It’s quite likely that IBM had a hand in writing the utility, but Microsoft probably maintained it and made sure it worked (more or less) on non-IBM systems. Continue reading →

Posted in DOS, PC architecture | Leave a comment