Category Archives: 386

Upcoming Fun

Posted on July 31, 2015 by Michal Necasek

Finally got one of these: There are pluses and minuses. Detailed report later.

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IBM XENIX: One Step Forward, One Step Back

Posted on March 29, 2015 by Michal Necasek

A while ago I wrote about why IBM PC XENIX 1.0 can’t work on any CPU other than a 286. But not content to leave well enough alone, I attempted to patch this version of XENIX so that it would … Continue reading →

Posted in 286, 386, IBM, VirtualBox, Xenix | 5 Comments

Windows 3.0 DR 1.14, February 1989

Posted on January 16, 2015 by Michal Necasek

Another rather interesting software artifact surfaced just recently, after more than 25 years since its release: Windows 3.0 Debug Release 1.14 (further referred to as DR 1.14) from February 1989. This was an alpha version only provided to select ISVs … Continue reading →

Posted in 386, Microsoft, PC history, Windows | 90 Comments

Original CEMM Unearthed

Posted on November 5, 2014 by Michal Necasek

An important fragment of PC history was unearthed a few days ago: An image of a Compaq Deskpro 386 supplemental disk from August 1986, containing among other things CEMM.EXE, Compaq’s original expanded memory emulator shipped with the Deskpro 386. The … Continue reading →

Posted in 386, Compaq, DOS | 28 Comments

386 Memory Managers and DMA

Posted on September 12, 2014 by Michal Necasek

A while ago I ran into an odd problem: A virtual machine running QEMM 9.0 (aka QEMM 97) would crash more or less every time it tried to read something from a floppy. No such problem was observable in any … Continue reading →

Posted in 386, Bugs, DOS, PC hardware | 7 Comments

Floating-Point Exceptions and DOS Extenders

Posted on September 5, 2014 by Michal Necasek

Recently I had a need to test the behavior of floating-point exceptions (FPEs) in environments where traditional FPE reporting is used. To briefly recap, in the original PC equipped with an 8088/8087 pair, floating-point exceptions, which are generally asynchronous events, were … Continue reading →

Posted in 386, Bugs, DOS, DOS Extenders, PC architecture | Leave a comment

IBM Blue Lightning: World’s Fastest 386?

Posted on August 22, 2014 by Michal Necasek

One of the OS/2 Museum’s vintage boards is a genuine Made in U.S.A. Alaris Cougar. These boards were produced by IBM for Alaris and are a bit unusual: There’s a small IBM DLC3 processor in plastic package soldered on board, … Continue reading →

Posted in 386, IBM, Intel, PC hardware, PC history | 62 Comments

Have You Seen This Board?

Posted on May 2, 2014 by Michal Necasek

The OS/2 Museum recently acquired this mystery 386 board (click on the image to see a high-resolution photo): This is in theory a killer 386 board: onboard Am386DX-40, a socket for a replacement 386 or 486DLC processor, a FPU socket, 256KB cache, … Continue reading →

Posted in 386 | 23 Comments

From the Annals of Branding

Posted on April 25, 2014 by Michal Necasek

The following picture shows four essentially identical Intel processors in the top row: The real difference is that some of them are fabricated on an older process and thus sport a larger die size than others. (They’re also not all … Continue reading →

Posted in 386, Intel | 14 Comments

386 ZIF Socket?

Posted on March 27, 2014 by Michal Necasek

I have a problem: Anyone familiar with 386 LIF (Low Insertion Force) sockets knows that the trouble isn’t installing the processors—that indeed doesn’t require much force and is easy to do. The real problem is getting the processor out without … Continue reading →

Posted in 386 | 18 Comments