Category Archives: PC history

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 | 25 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 | 43 Comments

ESDI Adventures

Posted on March 19, 2025 by Michal Necasek

At long last, I got hold of a decently well functioning ESDI drive. From my earlier adventures, I had a WD1007V-SE2 controller, as well as an older WD1007A. The WD1007A (Compaq branded) used to live in a Hyundai 286 machine … Continue reading →

Posted in ESDI, PC hardware, PC history, Seagate | 34 Comments

Learn Something Old Every Day, Part XIII: InDOS Is Not Enough

Posted on February 12, 2025 by Michal Necasek

The other day I spent a while trying to understand the purpose of a rather strange looking piece of code inside Borland’s THELP.COM utility shipped with Turbo Pascal 6.0 (THELP.COM was misbehaving under emulated DOS). The THELP utility performs the … Continue reading →

Posted in DOS, PC history, Undocumented | 14 Comments

The Other Three

Posted on January 2, 2025 by Michal Necasek

A previous blog post explored the semi-mysterious yet sometimes highly useful DOS APPEND command. Now it’s time to look at its relatives: ASSIGN, JOIN, and SUBST. ASSIGN ASSIGN is the oldest of the bunch. It was written by IBM and … Continue reading →

Posted in DOS, IBM, PC history | 13 Comments

IBM PC 5150 Model Numbers

Posted on September 24, 2024 by Michal Necasek

Recently I came across a minor mystery—the model numbers of the original IBM PC. For such a pivotal product, there is remarkably little detailed original information from the early days. When IBM started selling the PC, it used two methods … Continue reading →

Posted in IBM, PC hardware, PC history | 27 Comments

OS/2 2.0 Commitments

Posted on September 23, 2024 by Michal Necasek

Last week the OS/2 Museum received a rather interesting donation: a thick spiral bound document titled Third party commitment to IBM’s OS/2 Version 2.0, and labeled IBM COMDEX/SPRING ’92. The binder is a collection of about 250 press releases that … Continue reading →

Posted in IBM, Marketing, OS/2, PC history | 8 Comments

OS/2 2.11 SMP Woes

Posted on September 8, 2024 by Michal Necasek

IBM OS/2 V2.11 for Symmetric Multiprocessing (OS/2 2.11 SMP) was released in mid-1994 in response to Windows NT and its SMP support. The package was nothing more (and nothing less) than OS/2 V2.11 with support for SMP hardware. It was … Continue reading →

Posted in IBM, OS/2, PC history, SMP | 32 Comments