Category Archives: DOS

PC-MOS/386 Source Code

Posted on October 5, 2017 by Michal Necasek

I missed this when it was initially announced. The source code for PC-MOS/386 version 5.01 is now available on github under the GPLv3 license. It requires the user to supply Borland C++ 3.1 in order to build, but there are … Continue reading →

Posted in 386, DOS, Source code | 8 Comments

PC DOS 1.0, But Not Quite

Posted on May 26, 2017 by Michal Necasek

Last week a most interesting image of a 160K disk arrived at the OS/2 Museum. The files on the disk image are rather old. When the disk boots up (not trivial, see below), the following message appears: Astute readers will … Continue reading →

Posted in DOS, IBM, Microsoft, PC history, Pre-release | 47 Comments

Booting Is Hard

Posted on February 23, 2017 by Michal Necasek

So I had this brilliant idea of using SCSI drives with old 286/386/486 boards which have old BIOSes that can’t handle IDE drives bigger than 500-ish megabytes. The SCSI HBA is the first one I happened to grab, an Adaptec 1542C … Continue reading →

Posted in 386, BIOS, CompactFlash, DOS, SCSI | 21 Comments

MS C 4.0 Documentation Added

Posted on November 27, 2015 by Michal Necasek

Another library expansion. This time it’s Microsoft C 4.0 documentation (1986)—because it’s not available online, is not easy to find offline, and because Jeff asked for it. MS C 4.0 was an early Microsoft compiler, implementing first glimpses of the not-yet finalized … Continue reading →

Posted in C, Documentation, DOS, Microsoft | 7 Comments

The DOS 4.0 Shell Mouse Mystery

Posted on March 21, 2015 by Michal Necasek

Several years ago, I noticed that in some virtual and physical environments, the DOS Shell in both IBM’s and Microsoft’s DOS 4.0x has a very odd glitch: the mouse pointer moves, but does not register any clicks… except on scroll … Continue reading →

Posted in DOS, IBM, PC hardware, PC history | 28 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

Semantic Differences, Microsoft v. Microsoft

Posted on August 8, 2014 by Michal Necasek

While comparing the behavior of various versions of old Microsoft C compilers, I tried building a trivial hello-world type program with CL.EXE from Microsoft C/C++ 7.0 (March 1992) running on top of a 32-bit Windows Server 2003. This seemingly trivial … Continue reading →

Posted in DOS, Microsoft, Virtualization | 14 Comments

Multitasking MS-DOS 4.0, Goupil OEM

Posted on April 9, 2014 by Michal Necasek

The recently unearthed copy of the near-mythical Multitasking (aka European) MS-DOS 4.0 clearly did not want to be alone. James Lariviere, a kind reader of this blog, provided a disk image of multitasking DOS 4 which was released in 1986 … Continue reading →

Posted in DOS, Microsoft, OS/2 | 29 Comments