Author Archives: Michal Necasek

8×19 Text Mode Font Origins

Posted on August 15, 2025 by Michal Necasek

I was recently made aware of something that I had noticed before, but never paid much attention to. Consider this screenshot of a BIOS POST screen: VGA text modes usually use 720×400 resolution and 8×16 fonts (expanded to 9×16). The … Continue reading →

Posted in BIOS, Computing History, Intel | 38 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 | 79 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, Networking, OS/2, TCP/IP | 3 Comments

1990 Networking: LAN Manager 2.0

Posted on July 16, 2025 by Michal Necasek

In 1990, Microsoft released LAN Manager (LM) 2.0, a member of a long line of Microsoft’s networking products that started with MS-NET circa 1984 and eventually morphed into Windows NT file sharing. LAN Manager 1.0 was released in 1988 as … Continue reading →

Posted in 3Com, LAN Manager, Microsoft, Networking, PC history | 3 Comments

Learn Something Old Every Day, Part XVI: DOS 4.0 SELECT Is Too Clever

Posted on July 2, 2025 by Michal Necasek

A while ago I discovered an antique pirated copy of IBM DOS 4.00 on 5.25″ media, which was something that was missing in my archive. And by antique I mean from August 1988, when DOS 4.0 was practically brand new. … Continue reading →

Posted in Archiving, DOS, IBM, PC history | 17 Comments

Where Did CP852 Come From Again?

Posted on June 27, 2025 by Michal Necasek

An earlier article explored the history of codepage 852 (Latin-2 PC codepage) in released and pre-release versions of DOS and OS/2. At the time of this writing (June 2025), the earliest OS/2 build with some form of CP852 support including … Continue reading →

Posted in DOS, I18N, IBM, PC history | 28 Comments

Learn Something Old Every Day, Part XV: KEYB Is Half of Keyboard BIOS

Posted on June 16, 2025 by Michal Necasek

Recently I had an opportunity to reacquaint myself with the DOS KEYB utility. KEYB is interesting in that it is designed primarily for international users, but one can also run KEYB US to load KEYB with standard US layout. It … Continue reading →

Posted in BIOS, DOS, IBM, Keyboard | 11 Comments

1989 Networking: 3+Open LAN Manager 1.1

Posted on June 4, 2025 by Michal Necasek

The previously mentioned warez dump on archive.org contains a lot of little gems that would have been otherwise lost. One of those might be 3Com’s networking package from 1989, the 3+Open LAN Manager version 1.1. The software was released in … Continue reading →

Posted in 386MAX, 3Com, DOS, LAN Manager, Microsoft, Networking, OS/2 | 21 Comments

AI Responses May Include Mistakes

Posted on May 20, 2025 by Michal Necasek

The other day I wanted to look up a specific IBM PS/2 model, a circa 1992 PS/2 Server system. So I punched the model into Google, and got this: That did not look quite right, since the machine I was … Continue reading →

Posted in IBM, PS/2 | 27 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