Monthly Archives: August 2023

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, SCSI | 6 Comments

Learn Something Old Every Day, Part VIII: RTFM

Posted on August 22, 2023 by Michal Necasek

In my quest to understand the intricacies of x87 behavior and especially floating-point exceptions, I pulled out my trusty old Alaris Cougar board. The system board had a 100 MHz Intel OverDrive 486 DX4 plugged in and worked quite well. … Continue reading →

Posted in 486, Documentation, Intel, PC hardware, x87 | 9 Comments

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 | 20 Comments