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Category Archives: Documentation
Digging Into OS/2 2.0
The other day I had a “pressing” need to obtain the list of modules loaded in an OS/2 VM by examining the VM’s memory and CPU state. I was able to use existing code that worked on OS/2 V3.0 (Warp) … Continue reading
Posted in Debugging, Documentation, IBM, OS/2
21 Comments
Learn Something Old Every Day, Part XII: Strange File Resizing on DOS
Someone recently asked an interesting question: Why do Microsoft C and compatible DOS compilers have no truncate() and/or ftruncate() library functions? And how does one resize files on DOS? OK, that’s actually two questions. The first one is easy enough … Continue reading
Posted in Computing History, CP/M, Development, Documentation, DOS, Microsoft
29 Comments
VDS: Borne out of Necessity
In July 1990, Microsoft released a specification for Virtual DMA Services, or VDS. This happened soon after the release of Windows 3.0, one of the first (though not the first) providers of VDS. The VDS specification was designed for writers … Continue reading
Posted in 386, Documentation, Microsoft, PC history, Windows
10 Comments
Learn Something Old Every Day, Part VIII: RTFM
In my quest to understand the intricacies of x87 behavior and especially floating-point exceptions, I pulled out my trusty old Alaris Cougar board. The system board had a 100 MHz Intel OverDrive 486 DX4 plugged in and worked quite well. … Continue reading
Posted in 486, Documentation, Intel, PC hardware, x87
9 Comments
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
59 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
Compaq EGA Technical Reference Guide
A rater nice Compaq EGA Tech Ref recently turned up on archive.org, under the title COMPAQ Enhanced Color Graphics Board Technical Reference Guide. It’s from December 1986, relatively late in EGA’s life (given that it was about to be obsoleted … Continue reading
Posted in Compaq, Documentation, PC history
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Page Too Big
The other day I was able to look at an IBM OS/2 pre-release CD-ROM from early 1992. The CD-ROM appears to have been produced by IBM UK under the DAP (Developer Assistance Program) umbrella. The CD-ROM contains about 250 MB … Continue reading
Posted in Documentation, IBM, OS/2, PC history
4 Comments
Reconstructing the EGA BIOS
A few weeks ago I had a sudden need to understand certain finer points of the operation of EGA/VGA BIOS. I found common reference materials to be inadequate—they tend to do a good job of documenting the data structures the … Continue reading
Posted in BIOS, Development, Documentation, Graphics, IBM, PC history
32 Comments
Looking for High Sierra
Some time ago, I thought it would be useful to understand exactly what is the difference between CD-ROMs recorded in the old High Sierra format versus the ISO 9660 standard. This was in part spurred by the fact that I … Continue reading
Posted in CD-ROM, Documentation, PC history
23 Comments