Category Archives: Undocumented

SYSENTER, Where Are You?

Posted on July 20, 2017 by Michal Necasek

It has only recently been brought to my attention that Intel’s SYSENTER/SYSEXIT instructions have rather unusual past, and their origin is shrouded in mystery and confusion. One facet of the usage of these instructions is also a little unorthodox. Depending … Continue reading →

Posted in Intel, PC history, Undocumented | 26 Comments

Before OS/2 Was OS/2

Posted on February 5, 2016 by Michal Necasek

After almost 30 years, several disks with ancient builds of OS/2 surfaced. In this context, “ancient” means older than the May 1987 release of the first MS OS/2 SDK. In fact these disks are so old that the one thing … Continue reading →

Posted in IBM, Microsoft, OS/2, PC history, Undocumented | 39 Comments

386 LOADALL

Posted on January 7, 2016 by Michal Necasek

I recently came across hints suggesting that in the 1987 timeframe, Microsoft contemplated the use of the 386 LOADALL instruction in OS/2. As far as I know, no released version of OS/2 (including the SDK betas) utilized the 386 LOADALL. … Continue reading →

Posted in 386, Undocumented | 26 Comments

Sound Blaster DIAGNOSE and Disabled MPU-401

Posted on April 21, 2015 by Michal Necasek

Today I finally solved a nagging problem that always seemed like it had to have some sort of reasonable solution. Creative’s DIAGNOSE.EXE utility is quite useful when working with any Sound Blaster 16 derivatives (Sound Blaster 16, AWE32, Sound Blaster … Continue reading →

Posted in Creative Labs, Sound, Sound Blaster, Undocumented | 3 Comments