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Category Archives: Intel
Learn Something Old Every Day, Part VIII: RTFM
In my quest to understand the intricacies of x87 behavior and especially floating-point exceptions, I pulled out my trusty old Alaris Cougar board. The system board had a 100 MHz Intel OverDrive 486 DX4 plugged in and worked quite well. … Continue reading
Posted in 486, Documentation, Intel, PC hardware, x87
9 Comments
Failing to Fail
The other day I was going over various versions of the venerable DOS/16M DOS extender from Rational Systems (later Tenberry Software). The DOS/16M development kit comes with a utility called PMINFO.EXE which is meant to give the user some idea … Continue reading
Posted in Bugs, Intel, PC architecture, x87
11 Comments
Learn Something Old Every Day, Part VII: 8087 Intricacies
The other day I investigated a report that a C runtime library modification causes programs to hang on a classic IBM 5150 PC with no math coprocessor. The runtime originally contained two separate routines, one to detect the presence of … Continue reading
Posted in 8086/8088, Development, IBM, Intel, PC history, x87
10 Comments
Undefined Isn’t Unpredictable
The other day I discovered that 32-bit FreeBSD 11.2 has strange trouble running in an emulated environment. Utilities like ping or top would just hang when trying to print floating-point numbers through printf(). The dtoa() library routine was getting stuck … Continue reading
Posted in AMD, Development, Documentation, Intel
22 Comments
Does (E)IP Wrap Around in 16-bit Segments?
The 8086/8088 is a 16-bit processor and offsets within a 64K segment always wrap around. If a one-byte instruction at offset FFFFh is executed on an 8086, execution will continue at offset 0. This is simply a consequence of the … Continue reading
Posted in 386, 8086/8088, Intel, x86
9 Comments
IBM AIX for IA64 (Itanium) aka Project Monterey Runs Again!
(This is a guest post by Antoni Sawicki aka Tenox) Project Monterey was an attempt to unify the fragmented Unix market of the 90s in to a single, cross vendor Unix OS that would run on the upcoming Intel Itanium … Continue reading
XMVM Surgery
Last week I was prompted to take a look at the Intel Code Builder compiler from 1991, a 32-bit compiler targeting 386 extended DOS and shipping with its own DOS extender. It is what one might call an extremely obscure … Continue reading
Posted in 386, Development, Intel, PC history, Software Hacks
10 Comments
The IBM PC, 41 Years Ago
No, the OS/2 Museum does not have either a time machine or difficulty doing basic math. As of this writing, it is August 2021 and the IBM PC was announced in August 1981, 40 years ago. But in August 1980, … Continue reading
Posted in 8086/8088, BIOS, DOS, IBM, Intel, PC hardware, PC history
60 Comments
Nobody Expects…
…the Spanish Inquisition! Well, that too, but also nobody expects that a bland, run-of-the mill Novell NE2000 NDIS driver would crash/hang just because it runs on 486 or later CPUs. I wanted to try the “basic” DOS redirector shipped with … Continue reading
Posted in 486, Bugs, Intel, Microsoft
7 Comments
8237A DMA Page Fun
The other day I was trying to fill a couple of gaps in my understanding of the Intel 8237A DMA controller documentation. I wrote a small testcase that performed a dummy transfer and modified the base address and count registers … Continue reading
Posted in Intel, PC architecture, PC history
5 Comments