Category Archives: Microsoft

Pointedly Confusing

Posted on May 10, 2019 by Michal Necasek

While working on an unrelated problem, I stumbled across very surprising (to me) behavior of a C compiler. My code was the equivalent of the following: #include <stdio.h>int arr[42];int main( void ) { printf( “%u\n”, sizeof( &arr ) ); return( … Continue reading →

Posted in C, Microsoft | 9 Comments

LAN Manager 2.0 Primary Domain Controller

Posted on April 11, 2019 by Michal Necasek

While messing around with late 1980s and early 1990s networking software, I had the need to switch a LAN Manager 2.0 server to the primary domain controller role, so that it could run the Netlogon service and I could use … Continue reading →

Posted in LAN Manager, Microsoft, Networking | 3 Comments

FasterModeSwitch: Is It Really?

Posted on October 31, 2018 by Michal Necasek

Short answer: Yes. Before launching into the long answer, let’s recap what it even is. FasterModeSwitch is a SYSTEM.INI setting in Windows 3.1 which applies only to Standard (286) mode and can therefore be found in the [standard] section of … Continue reading →

Posted in 286, BIOS, Microsoft, Windows | 10 Comments

Crazy World

Posted on October 17, 2018 by Michal Necasek

After I successfully upgraded two Windows 10 VMs to the 1809 release at the beginning of October, I tried to do the same with more VMs and an actual laptop this week. But I couldn’t, no update was offered. While … Continue reading →

Posted in Bugs, Microsoft, Random Thoughts, Windows | 9 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

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 | 34 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

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

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

EXEPACK and the A20-Gate

Posted on March 23, 2018 by Michal Necasek

In 1991, DOS 5.0 brought about what’s perhaps the most common manifestation of A20 control trouble… Packed file is corrupt Microsoft published a KB article about this infamous error, but its author clearly did not understand the true cause of the … Continue reading →

Posted in Bugs, Microsoft, PC history | 19 Comments