Author Archives: Michal Necasek

This Code Smells of Desperation

Posted on August 5, 2023 by Michal Necasek

A few weeks ago I had the questionable pleasure of diving into the math exception handler of WIN87EM.DLL, the Windows 3.1 math emulator and FPU support library. Actually WIN87EM.DLL appears to have been first shipped with Windows 3.0, and the … Continue reading →

Posted in Bugs, Microsoft, PC architecture, x87 | 19 Comments

Retro-Porting to NT 3.1

Posted on July 26, 2023 by Michal Necasek

In another useless project, I decided to find out why even trivial programs created with the Open Watcom compiler refuse to run on Windows NT 3.1. Attempting to start an executable failed with foo.exe is not a valid Windows NT … Continue reading →

Posted in Development, Microsoft, NT, Watcom | 12 Comments

Retro-Porting to OS/2 1.0

Posted on July 20, 2023 by Michal Necasek

A few weeks ago I embarked on a somewhat crazy side project: Make the Open Watcom debugger work on OS/2 1.0. This project was not entirely successful, but I learned a couple of things along the way. The Open Watcom … Continue reading →

Posted in Development, IBM, Microsoft, OS/2, Watcom | 10 Comments

Failing to Fail

Posted on June 16, 2023 by Michal Necasek

The other day I was going over various versions of the venerable DOS/16M DOS extender from Rational Systems (later Tenberry Software). The DOS/16M development kit comes with a utility called PMINFO.EXE which is meant to give the user some idea … Continue reading →

Posted in Bugs, Intel, PC architecture, x87 | 11 Comments

Unintended Side Effects

Posted on May 23, 2023 by Michal Necasek

I’ve been lately trying to understand and improve the idling behavior of DOS programs and one of my guinea pigs has been the Open Watcom vi editor. While the 16-bit real-mode DOS variant of the editor idles nicely, the 32-bit … Continue reading →

Posted in Development, DOS Extenders | 1 Comment

IDLE DR-DOS

Posted on May 13, 2023 by Michal Necasek

I have a laptop. Sometimes I run VMs on it, and some of those VMs run DOS. When a DOS VM does not have any power management, the laptop quickly lets me know by kicking up the fan speed. It … Continue reading →

Posted in Computing History, Development, Digital Research | 9 Comments

Tracking Down a Bug

Posted on May 1, 2023 by Michal Necasek

When I first encountered the Unix vi editor many years ago, I recoiled in horror. It was nothing like the editors I was used to—Borland IDEs, DOS 5.0/6.x EDIT, or OS/2 and Windows editors. But over the years, I learned … Continue reading →

Posted in Debugging, Development, DOS, Watcom | 14 Comments

First ROM Shadowing

Posted on April 21, 2023 by Michal Necasek

The other day I was asked an interesting question: What was the first BIOS with support for ROM shadowing? In the 1990s, ROM shadowing was common, at first as a pure performance enhancement and later as a functional requirement; newer … Continue reading →

Posted in C&T, Compaq, IBM, PC architecture, PC history | 55 Comments

A wunderBAR Story

Posted on March 11, 2023 by Michal Necasek

Or, what should be broken became solid, and what should be solid became broken. While searching for something completely different, I came across a fascinating story of the “wunderBAR”. Since the story is very short, I’ll quote it here in … Continue reading →

Posted in Computing History, Corrections | 21 Comments

Hash Tables FTW

Posted on March 11, 2023 by Michal Necasek

Over the last few weeks I did a bit of tinkering on a hobby software project. The code was written by two other people during the last several years and I finally managed to find some time to fix a … Continue reading →

Posted in Development | 2 Comments