Monthly Archives: February 2012

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

Kernel Debugging with VirtualBox

Virtualization readily lends itself to debugging of low-level code that is difficult to analyze in conventional environments. It is also convenient for kernel debugging which would otherwise require two separate systems or at least a separate serial terminal. OS/2 Setting … Continue reading

Posted in Development, OS/2, VirtualBox | 4 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