Jumpy PS/2 mouse in Enhanced mode Windows 3.x

Posted on December 21, 2011 by Michal Necasek

There’s an interesting (and quite annoying) bug specific to Windows 3.x running in 386 enhanced mode (also known as Windows/386) and using a PS/2 mouse. In some situations, the mouse may jump to the top or the bottom of the screen, especially when the system is somewhat unresponsive. The cause of the jumpiness turns out to be a subtle bug in VKD (Virtual Keyboard Device), a virtual device (VxD) which is part of Windows/386.

The way PS/2 mouse input is handled in Windows/386 is extraordinarily complex. The mouse driver (MOUSE.DRV) simply uses the BIOS INT 15h, sub-function C2h interface to register a mouse callback routine. The BIOS uses IRQ 12 and I/O ports 60h/64h to read data from the mouse. However, the VKD VxD inserts a whole new layer between the BIOS and the mouse hardware. Continue reading →

Posted in Windows | 7 Comments

Simple Windows NT video miniport for VirtualBox

Posted on December 18, 2011 by Michal Necasek

A few months ago, I developed a trivial video miniport for use in Windows NT virtual machines. The primary goal was to improve display speed and get past the 800×600, 16 color display mode which is the maximum Windows NT (up to an including Windows 2000) can handle out of the box on “modern” hardware. The miniport is designed to work with the synthetic SVGA “hardware” emulated by VirtualBox.

A secondary objective was to write the miniport in such a way that as many Windows NT versions could be supported with a single binary. That objective was fulfilled beyond expectations; the driver binary works with every x86 version of NT from the initial July 1993 release of Windows NT 3.1 up to and including Windows 7 released in October 2009. Windows 8 appears to drop the video miniport interface and thus cannot be supported. Continue reading →

Posted in NT, VirtualBox | 26 Comments

Microsoft OS/2 1.0 user documentation

Posted on December 17, 2011 by Michal Necasek

In late 1987, Microsoft shipped a set of OS/2 1.0 user documentation as part of the OS/2 SDK. The set included the Setup Guide, Beginning User’s Guide (a tutorial style document), and User’s Reference. The manuals were similar in style to DOS documentation from that era and likely produced on XENIX using the standard UNIX document production tools (i.e. troff and related utilities).

The manuals shipped by Microsoft were not entirely finished. Some of the more involved explanations were incomplete, screenshots were missing, and a few illustrations weren’t provided. That said, end users were not expected to see those manuals. Instead, OEMs would adapt (or completely rewrite) the OS/2 documentation provided by Microsoft. Continue reading →

Posted in Documentation, OS/2 | 3 Comments

Converting NT DDK/SDK PostScript documents to PDF

Posted on November 19, 2011 by Michal Necasek

Pre-releases of Microsoft’s NT development tools, as well as the final NT 3.1 SDK and DDK, shipped with a full set of printable documentation in PostScript format. The PostScript book-style document were rather more pleasing to the eye than the WinHelp format, and especially for the explanatory “guide” material, some readers found them much nicer to work with.

But really, who wants thousands of pages of dead tree matter? The complete SDK/DDK documentation set ran to somewhere in the 10,000 pages range. It should be easy to convert the PostScript documents to PDFs and obtain a nice set of easily viewable and searchable documents. It should be easy… It’s anything but. Continue reading →

Posted in Documentation, NT | 5 Comments

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 | 14 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 | 8 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