Category Archives: IBM

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 | 59 Comments

The A20-Gate: It Wasn’t WordStar

Posted on March 16, 2018 by Michal Necasek

Although WordStar was long suspected to be the reason (or at least one of the major reasons) for implementing the A20 gate hardware on the PC/AT and all the associated problems later on, it is now all but certain that … Continue reading →

Posted in 286, IBM, Microsoft, PC history, WordStar | 36 Comments

Pascal Out Of Memory

Posted on February 23, 2018 by Michal Necasek

Suppose you want to run the original 1981 vintage IBM Pascal 1.0 (supplied by Microsoft) on a PC that is less than 30 years old. Upon execution, PAS1.EXE may well fail with the following error: Error: Compiler Out Of Memory … Continue reading →

Posted in Bugs, Corrections, IBM, Microsoft, PC history | 40 Comments

Audio Frequency Data Acquisition

Posted on August 23, 2017 by Michal Necasek

Readers of this blog may have noticed that besides OS/2 software, I have interested in PC sound cards. I thought I had a decent idea about the major milestones in PC sound history, but I had to perform a few … Continue reading →

Posted in IBM, MCA, PC hardware, PC history, PS/2, Sound, Sound Blaster | 14 Comments

PC DOS 1.0, But Not Quite

Posted on May 26, 2017 by Michal Necasek

Last week a most interesting image of a 160K disk arrived at the OS/2 Museum. The files on the disk image are rather old. When the disk boots up (not trivial, see below), the following message appears: Astute readers will … Continue reading →

Posted in DOS, IBM, Microsoft, PC history, Pre-release | 43 Comments

OS/2 2.0, Xmas ’91 Edition

Posted on April 26, 2017 by Michal Necasek

After reviewing the OS/2 2.0 level 6.605 pre-release, another re-discovery is the “Limited Availability” (LA) level 6.177 from December 1991. This was the last OS/2 2.0 pre-release of 1991 and also the last one using the 6.1xx numbering; the next pre-release was … Continue reading →

Posted in 386, IBM, OS/2, PC history | 15 Comments

OS/2 2.0, Summer ’91 Edition

Posted on April 5, 2017 by Michal Necasek

In a fascinating example of poor timing, disk images of OS/2 2.0 pre-release level 6.605 from July/September 1991 were missing for over 25 years, only to show up literally one day after after the 25th anniversary of the OS/2 2.0 release … Continue reading →

Posted in 386, IBM, OS/2, PC history | 35 Comments

OS/2 2.0 at 25

Posted on March 31, 2017 by Michal Necasek

Twenty-five years ago, on March 31st, 1992, IBM released OS/2 2.0, the first mass-market 32-bit PC operating system. The road to OS/2 2.0 was quite long and winding, and the OS was a proud member of the vaporware club (just like, … Continue reading →

Posted in 386, IBM, Microsoft, OS/2 | 33 Comments

IBM XENIX: Two Steps Forward

Posted on March 16, 2017 by Michal Necasek

There are reasons to revisit an old topic. Very old, considering that IBM Xenix 1.0 was released in 1984, well over 30 years ago. To recap, this version of Xenix is unique in that it runs only on 286 processors. It … Continue reading →

Posted in 286, IBM, VirtualBox, Xenix | 13 Comments

Deskpro 386 at 30

Posted on September 26, 2016 by Michal Necasek

30 years ago, in September 1986, Compaq announced the Deskpro 386, a PC as revolutionary as it was conservative. Compaq decided to forge its own path and not wait for IBM to introduce a 386-based PC. At the same time, Compaq … Continue reading →

Posted in 386, Compaq, IBM, PC history, PC press | 17 Comments