Category Archives: Development

Windows 3.x VDDVGA

While working on my Windows 3.x display driver, I ran into a vexing problem. In Windows 3.1 running in Enhanced 386 mode, I could start a DOS session and switch it to a window. But an attempt to set a … Continue reading

Posted in 386, Development, Documentation, Graphics, PC history, Windows | 19 Comments

Learn Something Old Every Day, Part VII: 8087 Intricacies

The other day I investigated a report that a C runtime library modification causes programs to hang on a classic IBM 5150 PC with no math coprocessor. The runtime originally contained two separate routines, one to detect the presence of … Continue reading

Posted in 8086/8088, Development, IBM, Intel, PC history, x87 | 7 Comments

A House of Cards

As one step in the development of the Windows 3.x/2.x display driver, I needed to replace a BIOS INT 10h call to set the video mode with a “native” mode set code going directly to the (virtual) hardware registers. One … Continue reading

Posted in Bugs, Development, Microsoft, Windows | 48 Comments

Win16 Retro Development

Several months ago I had a go at producing a high resolution 256-color driver for Windows 3.1. The effort was successful but is not yet complete. Along the way I re-learned many things I had forgotten, and learned several new … Continue reading

Posted in Debugging, Development, Microsoft, Windows | 24 Comments

Undefined Isn’t Unpredictable

The other day I discovered that 32-bit FreeBSD 11.2 has strange trouble running in an emulated environment. Utilities like ping or top would just hang when trying to print floating-point numbers through printf(). The dtoa() library routine was getting stuck … Continue reading

Posted in AMD, Development, Documentation, Intel | 22 Comments

Antique Display Driving

Here’s a preview of something I’ve been slowly working on, bit by bit: That screenshot surely looks a little funny. That’s because it is Windows 1.04 running with a heavily modified 256-color Windows 3.x display driver, using resources from a … Continue reading

Posted in Development, Microsoft, Windows | 34 Comments

Learn Something Old Every Day, Part VI: Backward Buffer Overwrite

A few days ago I spent far too much time debugging a largish piece of 16-bit Windows code written in assembler. I found a scenario where (fortunately fairly reproducibly) Windows crashed because the internal state of a DLL got corrupted. … Continue reading

Posted in Bugs, Development, Windows | 24 Comments

Windows 9x Video Minidriver Source Code

As promised, here is the source code for the Windows 9x VirtualBox display minidriver. For discussion of the source code, see the included readdev.txt file. The code was developed on a Windows 10 host system. For extra credit, I attempted … Continue reading

Posted in Development, Source code, VirtualBox, Watcom, Windows 95 | 16 Comments

Windows 9x Video Minidriver HD+

The OS/2 Museum has made available the first version of a display driver disk for Windows 9x running on VirtualBox. The driver uses a linear framebuffer and supports 8/16/24/32bpp modes with resolutions up to 1920×1200 pixels (see more below). The … Continue reading

Posted in Development, VirtualBox, Watcom, Windows 95 | 52 Comments

The Strange Case of GetEnvironmentStringsA

It was recently pointed out to me that a simple “hello world” style application built with Open Watcom C/C++ 1.9 does not run on Win32s version 1.30, even though the same executable runs just fine on Windows NT 3.51, Windows … Continue reading

Posted in Development, NT, Watcom | 17 Comments