Author Archives: Michal Necasek

Book Review: Unauthorized Windows 95

Posted on October 9, 2014 by Michal Necasek

A Few Decades Late Book Reviews Unauthorized Windows 95 Developer’s Resource Kit, by Andrew Schulman IDG Books, November 1994; 593 pages, ISBN 1-56884-305-4; $39.99 A testimony to the incredible level of hype surrounding Microsoft’s “Chicago”, Unauthorized Windows 95 was published nearly a year before … Continue reading →

Posted in Books, DOS Extenders, Windows 95 | 16 Comments

Installing Windows 95 on SCSI in a VM

Posted on September 26, 2014 by Michal Necasek

For the adventurous, it is possible to install Windows 95 in a VM configured with SCSI storage (hard disk, CD-ROM) attached to an emulated BusLogic HBA. This works in VirtualBox, but there’s a catch—the emulated PCI BusLogic HBA must have … Continue reading →

Posted in BusLogic, SCSI, VirtualBox, Windows 95 | 7 Comments

Forward Compatibility, Landmines

Posted on September 20, 2014 by Michal Necasek

Several years ago, after attempting to get a very old 286 version of Xenix running in a VM, I concluded that it was probably incompatible with any 386 and later processor. Recently I revisited this issue and examined the problem … Continue reading →

Posted in 286, Intel, Xenix | 32 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

OS/2 Kernel Debugger and MVDM Interrupts

Posted on August 29, 2014 by Michal Necasek

While working on an unrelated problem, I noticed a strange behavior of one of my OS/2 VMs running OS/2 Warp 4.52. To cut a long story short, if an unhandled floating-point exception occurred in a DOS window (VDM, or Virtual … Continue reading →

Posted in Bugs, Debugging, OS/2 | 12 Comments

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

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

NT Video Miniport for VirtualBox, With Source Code

Posted on August 1, 2014 by Michal Necasek

Note: See also an updated version. Upon reader request, the OS/2 Museum is publishing the source code to the NT video miniport driver for VirtualBox. To recap, this is a NT video miniport which allows 32-bit NT versions to use high-resolution graphics … Continue reading →

Posted in Graphics, NT, Source code, VirtualBox | 48 Comments

Windows Presentation Manager Documentation

Posted on July 20, 2014 by Michal Necasek

The OS/2 Museum just posted a three-volume set of draft Windows Presentation Manager reference documentation. This refers to the OS/2 Presentation Manager GUI but highlights the story Microsoft pushed in 1987: Windows and OS/2 both used the same graphical user … Continue reading →

Posted in Documentation, Microsoft, OS/2 | 5 Comments