Author Archives: Michal Necasek

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

Three Weeks

Posted on July 27, 2018 by Michal Necasek

I happen to own several old laptops, now about 10 years old, that had the misfortune of being delivered with a Windows Vista license and matching Windows Vista OEM installations on their recovery partitions/media. About a year ago, I noticed … Continue reading →

Posted in Bugs, Microsoft, Windows | 27 Comments

How Fast Is a PS/2 Keyboard?

Posted on July 23, 2018 by Michal Necasek

A few weeks ago, an interesting question cropped up: How fast is a PS/2 keyboard? That is to say, how quickly can it send scan codes (bytes) to the keyboard controller? One might also ask, does it really matter? Sure … Continue reading →

Posted in Borland, IBM, Keyboard, PC hardware | 14 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

ANOMALY: meaningless REX prefix used

Posted on June 20, 2018 by Michal Necasek

While trying to get work done, I was confronted by several disturbing messages printed on the console of a 64-bit Windows 7 system: [0x7FEEFEFAAA0] ANOMALY: meaningless REX prefix used [0x7FEEFEE48C0] ANOMALY: meaningless REX prefix used [0x7FEEFEE54B0] ANOMALY: meaningless REX prefix used This … Continue reading →

Posted in Bugs, Debugging | 9 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 | 19 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

ICEBP Finally Documented

Posted on May 25, 2018 by Michal Necasek

After more than 30 years, Intel finally documented the INT1 instruction, also known as ICEBP (opcode F1h), in the latest (May 2018, -067) edition of the SDM. This was probably forced by security concerns, because from a security standpoint, having … Continue reading →

Posted in 386, Documentation, Intel, Undocumented | 14 Comments