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Category Archives: x86
Better Late Than Never
Better late than never, although in this instance, it’s really really late—about thirty years late. In the world of computing, that is eternity. The talk is about the new CR4.UMIP control bit documented in the latest (revision 58) Intel SDM, … Continue reading
Posted in 286, Intel, x86
11 Comments
Curious Instructions
Years ago, Geoff Chappell (the author of DOS Internals, among other things) published an article about mysterious instructions that Microsoft’s LINK knows but Intel’s documentation is silent about. The fourteen listed instructions were: LOADALL, CFLSH, WRECR, RDECR, SVDC, RSDC, SVLDT, … Continue reading
Posted in Documentation, Intel, x86
11 Comments
Undocumented 8086 Opcodes
A minor mystery recently surfaced while analyzing DOS boot sectors. DOS uses several criteria when deciding whether a boot sector contains a valid BPB, and one of the criteria is (oddly enough) checking whether the first two bytes of the … Continue reading
Posted in 8086/8088, Documentation, Intel, x86
57 Comments
LOADALL Strikes Again
A minor mystery recently popped up while running IBM’s OS/2 1.1 (1988), the first OS/2 version with the Presentation Manager GUI. While Microsoft’s and IBM’s releases of OS/2 were fully compatible from application perspective, there were differences in the drivers … Continue reading
BSD Buglets
Last week I ran into two wholly unrelated problems while researching the history of BSD-derived Unix systems on PCs. Both are classics in their category and merit a closer look. Y2K Strikes Again The first issue is a very typical … Continue reading
Posted in BSD, UNIX, x86
11 Comments
If you ENTER, you might not LEAVE
I’ve recently spent some time debugging curious hangs/aborts in two more or less exotic operating systems, Plan 9 and QNX 4.25. Both turned to be caused by the same innocuous-looking BIOS change, even though the circumstances were somewhat different and … Continue reading
Posted in Intel, x86
9 Comments
Windows NT BSOD Aclock Port
Do you remember the famous Windows NT Blue Screen Of Death? For years it was a source of jokes and bad reputation of Windows reliability. There even was a Blue Screen Saver! Today we fortunately see much less of it, but it … Continue reading
Posted in 386, Development, NT, VGA, Windows, x86
10 Comments
Solaris 2.5.1 and 2.6 crashes on modern Intel CPUs
I recently found that Solaris 2.6 and 2.5.1 does not work when run in a VM on a modern Intel CPU (Sandy Bridge generation Core i7), or to be exact fails most of the time (about nine times out of … Continue reading
Posted in Solaris, VirtualBox, Virtualization, x86
20 Comments
64-bit trouble with Solaris 10 U4 and earlier
On many newer systems, Solaris 10 releases up to and including Solaris 10 8/07 (that is Update 4, also known as S10U4) behave in an unhelpful manner. The installer can be launched from CD or DVD and the system can be … Continue reading
Posted in Solaris, x86
12 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