Category Archives: Bugs

When Networking Doesn’t Work

Posted on May 4, 2026 by Michal Necasek

Last week I spent far too much time trying to get my Windows 11 machine to talk to an antique Tyan SMDC (Server Management Daughter Card) IPMI module over the network. At first, I tried Tyan’s own old TSO (Tyan … Continue reading →

Posted in Bugs, Intel, IPMI, Networking, PC hardware, TCP/IP | 2 Comments

Wait here. No, wait here!

Posted on November 11, 2025 by Michal Necasek

While working on a hobby project, I set up an OS/2 MCP2 (Convenience Package 2 for OS/2 Warp 4) virtual machine with a debug kernel and an expectation that I’d reboot the VM a lot. I was disturbed to find … Continue reading →

Posted in Bugs, Debugging, OS/2 | 6 Comments

More than Two Hard Disks in DOS

Posted on July 22, 2025 by Michal Necasek

Investigating the rather odd behavior of the Microsoft OS/2 1.21 disk driver led me to Compaq and their EXTDISK.SYS driver. While experimenting with various setups, I realized that DOS versions older than 5.0 do not support more than two hard … Continue reading →

Posted in Bugs, Compaq, DOS, Microsoft, PC history | 84 Comments

Learn Something Old Every Day, Part XVII: DHCP and ARP Don’t Mix in WSA SMP

Posted on July 19, 2025 by Michal Necasek

I just spent an inordinate amount of time debugging a VM running OS/2 Warp Server Advanced SMP (WSA SMP). The VM was working fine (except for sometimes hanging very early during boot, a known issue with the SMP kernel), but … Continue reading →

Posted in Bugs, IBM, LSOED, Networking, OS/2, TCP/IP | 3 Comments

Compaq EXTDISK.SYS

Posted on April 16, 2025 by Michal Necasek

This is a follow-up to a previous post about the curious driver in Microsoft OS/2 1.21. After initially writing the article, additional information came to light, explaining why the code was there. In summer 1988, Compaq released the Deskpro 386/25, … Continue reading →

Posted in Bugs, Compaq, DOS, PC history, Storage | 32 Comments

The Strange MS OS/2 1.21 Disk Driver

Posted on April 11, 2025 by Michal Necasek

Attempting to install Microsoft OS/2 1.21 will fail on many systems with the following scary looking error: Pressing Enter as directed shows the following more detailed error message: The initial boot phase, as well as the installation stage immediately before … Continue reading →

Posted in Bugs, Microsoft, OS/2, PC history | 44 Comments

Time Trouble

Posted on March 7, 2025 by Michal Necasek

Last Friday I had a moment of panic. While investigating why different run-time libraries might interpret file timestamps differently, I noticed that even Windows doesn’t always agree with itself. When was dos4gw.exe last modified, at 10:14 PM or 9:14 PM? … Continue reading →

Posted in Bugs, Development, Microsoft | 20 Comments

I Thought I Found a Bug…

Posted on December 25, 2024 by Michal Necasek

So I was working on improving a DOS emulator, when I found that something seemingly trivial wasn’t working right when COMMAND.COM was asked to do the following: echo AB> foo.txtecho CD>> foo.txt Instead of ABCD, foo.txt contained ABBC. I verified … Continue reading →

Posted in Bugs, C, Development, Watcom | 26 Comments

Learn Something Old Every Day, Part X: The VGA Attribute Controller Is Weird

Posted on May 3, 2024 by Michal Necasek

A few days ago I finally swatted a VGA emulation bug that I had known about for several years, but couldn’t identify until recently. The problem affected only Windows 3.1 running in Standard mode. It did not occur in Windows … Continue reading →

Posted in Bugs, LSOED, PC hardware, VGA | 10 Comments

Learn Something Old Every Day, Part IX: AHA-154xB and ASPI4DOS.SYS

Posted on August 31, 2023 by Michal Necasek

The other day I had a pressing “need” to examine the behavior of Adaptec 154x and compatible SCSI HBAs and their DOS drivers. I found the hard way that the AHA-154xB does not work with Adaptec’s last DOS drivers from … Continue reading →

Posted in Adaptec, Bugs, BusLogic, LSOED, SCSI | 8 Comments