Monthly Archives: July 2025

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 | 53 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 | 2 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