Author Archives: Michal Necasek

MS-DOS 1.1, 2.0 Source Code Released

Posted on March 25, 2014 by Michal Necasek

In cooperation with the excellent Computer History Museum in Mountain View, Microsoft released the source code to MS-DOS 1.1, MS-DOS 2.0, and Microsoft Word for Windows 1.1a. Here’s hoping that this is a sign of things to come and Microsoft … Continue reading →

Posted in DOS, Microsoft, PC history | 53 Comments

IBM OS/2 1.0 in a VM

Posted on March 21, 2014 by Michal Necasek

As previously mentioned, IBM’s OS/2 1.0 and 1.1 is extra unfriendly to modern hypervisors. To recap, there is a curious difference between IBM’s and Microsoft’s kernels in OS/2 1.0/1.1 with regard to mode switching. For reasons that aren’t very clear, … Continue reading →

Posted in IBM, Microsoft, OS/2, VirtualBox, Virtualization | 36 Comments

What’s in a Name?

Posted on March 7, 2014 by Michal Necasek

The following four processors are much more similar than one might think: 486 aficionados will recognize the processors made by IBM, ST Microelectronics, and Texas Instruments to be essentially one and the same model—Cyrix 486DX.

Posted in 486, Cyrix | 14 Comments

Kids These Days, Continued

Posted on February 28, 2014 by Michal Necasek

As the OS/2 museum pointed out, many kids these days don’t really know how to properly use floppies. Fortunately, not all is lost and at least some youngsters know exactly what to do with a 3½” diskette. First, firmly hold … Continue reading →

Posted in Floppies | 6 Comments

Soyo SY-4SAW2 Notes

Posted on February 26, 2014 by Michal Necasek

Following is a list of notes describing several less-than-obvious features and characteristics of the Soyo SY-4SAW2 486 VIP motherboard. This is a latter-day 486 board based on the SiS 496/497 chipset, notable for PS/2 mouse support and the ability to … Continue reading →

Posted in 486, PC hardware | 8 Comments

Untested Error Paths

Posted on February 20, 2014 by Michal Necasek

About a week ago I revived an old Sony VAIO laptop (model PCG-R505TS) that hadn’t been used for a few years. It had lost CMOS contents so I had to re-enter the date and adjust a few BIOS settings. The … Continue reading →

Posted in PC hardware, Windows | 3 Comments

Soyo 4SAW2: Why So Slow?

Posted on February 15, 2014 by Michal Necasek

Continuing to go through my junk pile, I unearthed a Soyo SY-4SAW2 motherboard. This is a late 1995 vintage 486 ISA/VLB/PCI motherboard with a SiS 85C496/497 chipset. It’s a classic Baby AT board with an AT keyboard connector, although it … Continue reading →

Posted in PC hardware | 21 Comments

Butterfly Conservation

Posted on February 8, 2014 by Michal Necasek

The OS/2 Museum recently acquired one of the famous IBM 701 ThinkPads, commonly nicknamed “Butterfly” thanks to the fold-out keyboard. Unfortunately, the unit suffered a fate common to many old ThinkPads—battery leakage. The unit would power on, but it had … Continue reading →

Posted in PC hardware, ThinkPad | 3 Comments

Have You Ever Used One of These?

Posted on January 31, 2014 by Michal Necasek

Still on the theme of unusual hardware… in my junk pile there’s one of these rather special little parts: As the label on the PCB says, this is a 486 pod for a Periscope IV debugger. The Periscope Company of … Continue reading →

Posted in Debugging, PC hardware | 38 Comments

Early PCI Board

Posted on January 28, 2014 by Michal Necasek

Since some of this blog’s readers are very good at recognizing obscure hardware, I thought I’d post photos of one more somewhat exotic graphics card: This board was one of the early PCI graphics adapters. It’s old enough that it … Continue reading →

Posted in Graphics, PC hardware | 27 Comments