Category Archives: PC history

The History of a Security Hole

Posted on August 31, 2018 by Michal Necasek

Warning: If you do not care for the finer points of x86 architecture, please stop reading right now—in the interest of your own sanity. A while ago I was made aware of a strange problem causing a normal user process … Continue reading →

Posted in 386, BSD, Bugs, Documentation, PC history | 44 Comments

A Sound Card Before Its Time

Posted on August 15, 2018 by Michal Necasek

A mysterious full-length sound card recently arrived at the OS/2 Museum. It was clearly manufactured by IBM in 1985, and sports a 20 MHz Texas Instrument TMS32010 DSP (the DSP is the large black DIP chip near the lower left … Continue reading →

Posted in IBM, PC history, Sound | 20 Comments

OS/2 2.0, Spring ’91 Edition

Posted on July 10, 2018 by Michal Necasek

Thanks to a generous reader, a curiously nondescript box labeled “OS/2 32-Bit Pre-release” recently turned up at the OS/2 Museum. The box looks very much like retail IBM products from the early 1990s, but has no identifying description except for … Continue reading →

Posted in IBM, Microsoft, OS/2, PC history, Pre-release | 35 Comments

A Brief History of Unreal Mode

Posted on June 15, 2018 by Michal Necasek

After a run-in with a particularly crazy manifestation of unreal mode (Flat Assembler, or fasm), I decided to dig deeper into the history of this undocumented yet very widely used feature of 32-bit x86 processors. For the purposes of this … Continue reading →

Posted in 386, Corrections, Microsoft, PC history, Undocumented | 47 Comments

USB 0.9

Posted on June 2, 2018 by Michal Necasek

A couple of months ago I lamented the fact that historic USB documentation appears to have vanished from the face of the Earth. Today I finally found one such document, the USB 0.9 specification from April 13, 1995, published almost … Continue reading →

Posted in Documentation, PC history, USB | 30 Comments

Troubled Time

Posted on May 30, 2018 by Michal Necasek

This is not an article about current affairs Over the last few weeks, I had several interesting run-ins with time, specifically how time is represented and processed by computers. Deep down it’s really all about a clash of human culture … Continue reading →

Posted in Bugs, PC history, Random Thoughts | 18 Comments

A Word on the CALL 5 Spell

Posted on May 26, 2018 by Michal Necasek

After years of searching for some reasonably widespread DOS application which used the CP/M-style CALL 5 interface and coming up with absolutely nothing, Jeff Parsons of pcjs.org found one: None other than Microsoft Word, specifically the spell checker in the … Continue reading →

Posted in DOS, Microsoft, PC history | 10 Comments

SpaceMaker Update

Posted on May 17, 2018 by Michal Necasek

Jeff Parsons has been able to locate an executable compressed with Realia SpaceMaker which significantly pre-dates all hitherto known SpaceMaker or EXEPACK survivors. It’s an editor called DVED.COM version 6.02, found on disk 191 of the PC-SIG Library 8th Edition … Continue reading →

Posted in PC history | 10 Comments

Realia SpaceMaker

Posted on April 30, 2018 by Michal Necasek

A recent exploration of Microsoft’s EXEPACK posed the question whether EXEPACK was the first executable compressor, at least in the world of PCs. It wasn’t. That distinction almost certainly belongs to Realia SpaceMaker, which was probably released sometime in late … Continue reading →

Posted in Compression, Development, PC history | 12 Comments

The A20-Gate Fallout

Posted on April 13, 2018 by Michal Necasek

A recent post explored the motivation (i.e. backwards compatibility) to implement the A20 gate in the IBM PC/AT. To recap, the problem IBM solved was the fact that 1MB address wrap-around was an inherent feature of the Intel 8086/8088 CPU, … Continue reading →

Posted in IBM, Microsoft, PC architecture, PC history | 93 Comments