Monthly Archives: April 2018

Realia SpaceMaker

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

Undocumented RDTSC

The other day I wrote a simple DOS program which used the RDTSC instruction in order to obtain precise time measurements (of how long it takes a PS/2 keyboard to send data; more about that some other time). The 16-bit … Continue reading

Posted in Documentation, Intel, Pentium | 15 Comments

The A20-Gate Fallout

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

Any Readers in Central Italy?

This is a very long shot, but maybe someone can help me. I’d very much like to buy a piece of used electronics for sale in Italy (L’Aquila province). Unfortunately the seller requires a local pick-up. I don’t live exactly … Continue reading

Posted in Random Thoughts | 3 Comments