Category Archives: Windows

From a Feature to a Bug

Sometimes the quest for backwards compatibility has unintended consequences. In some cases, the presumably beneficial backwards compatibility turns into a source of problems. The costs end up far outweighing the benefits, yet the “feature” may be difficult to get rid … Continue reading

Posted in DOS, PC history, Windows | 13 Comments

AVX support disrupts WoW64 debugging

Sometimes, the old and the new intersect in unexpected ways. After upgrading to a Sandy Bridge based system (Core i7) and Windows 7 SP1 64-bit some time ago, I noticed that debugging exceptions in 32-bit user programs didn’t quite work … Continue reading

Posted in Windows, x86 | 18 Comments

LAN Manager vs. Windows 7

I recently spent some time trying to access disks shared by a Windows 7 machine from various versions of OS/2 (running in VMs, although that’s not really relevant). The OS/2 clients ranged from OS/2 1.3 with LAN Manager 2.1 (1991 … Continue reading

Posted in Networking, OS/2, Windows | 28 Comments

Undocumented VflatD

The virtual flat framebuffer driver, or VflatD, was introduced in Windows 95 in order to ease development of display drivers. It was surprisingly poorly documented and the sample drivers did not illustrate its use very well. A short backgrounder may … Continue reading

Posted in Documentation, VGA, Windows | 2 Comments

How to please WDCTRL

As any user of 16-bit Windows knows, Microsoft Windows 3.1x in 386 Enhanced mode supported a coveted feature called 32-bit disk access (sometimes also called FastDisk). The “32-bit” designation was slightly misleading as there was no 32-bit data path to … Continue reading

Posted in BIOS, Windows | 3 Comments

Retro development with aclock

In the past few days, I embarked upon a project to port Antoni Sawicki’s aclock, a small text-based clock program (aclock stands for analog clock), to 16-bit Windows. While aclock itself has been ported to over 150 platforms, it is a … Continue reading

Posted in Development, PC history, Windows | 14 Comments

Jumpy PS/2 mouse in Enhanced mode Windows 3.x

There’s an interesting (and quite annoying) bug specific to Windows 3.x running in 386 enhanced mode (also known as Windows/386) and using a PS/2 mouse. In some situations, the mouse may jump to the top or the bottom of the … Continue reading

Posted in Windows | 7 Comments

Windows/386 2.01

The OS/2 museum recently obtained a boxed copy of the original Microsoft Windows/386. That is, version 2.01 of Windows/386 from September 1987. Windows/386 was Microsoft’s first product utilizing the 386 hardware in the DOS world. Microsoft was involved in the … Continue reading

Posted in PC history, Windows | 34 Comments

The IHC Damage

Trying to sort through a heap of floppy images recently, I found many of them to contain a suspicious ‘IHC’ signature in their boot sector in the location where an OEM identifier (such as ‘IBM  3.3’ or ‘MSDOS5.0’ would normally … Continue reading

Posted in DOS, Windows, Windows 95 | 5 Comments

Display Drivers, OS/2 and 16-bit Windows

Not surprisingly, the display driver model of Windows 1.x/2.x/3.x and OS/2 1.x/2.x was quite similar. This was in sharp contrast to the drivers for just about every other device; while disks or network adapters already had existing drivers in DOS, … Continue reading

Posted in OS/2, Windows | Leave a comment