19
votes
Intel 80188 & 8087 clock frequency differences
The 8087 datasheet specifies which versions can be used with the 80188/80186. There were three versions of the 8087: the 5MHz 8087, the 8MHz 8087-2, and the 10MHz 8087-1. The recommended NPU for use ...
- 118k
16
votes
Accepted
What did it cost the 8086 to support unaligned access?
The Missing Angle
It feels a bit like the question misses the most important point about the whole 8086 project over discussing implementation details:
8080/85 compatibility
The 8086 was intended as a ...
- 213k
12
votes
Did x86 CPU vendors like Intel, NEC, AMD, and Cyrix provide their own debugger for DOS with better CPU support and was it free?
No. While DOS competitors did improve on various DOS commands to try and differentiate their products from Microsoft's there was no equivalent motivation for CPU manufacturers whose products were used ...
- 389
10
votes
Intel 80188 & 8087 clock frequency differences
Looking at the mentioned page (3-5) it clearly states that it's a 'Typical System Diagram':
It is not in any way detailed schematic to be built nor suggesting or even listing specific components. It'...
- 213k
10
votes
Difference between the 8255 and 8042 PPIs
The 8042 is no PIO chip at all, but essentially a (very small) full-blown computer on a chip - a microcontroller. It contains a small amount of RAM (256 Bytes), ROM (4K, One-time-programmable or ...
- 33k
10
votes
Accepted
Undocumented ModR/M byte combinations
As part of his series about the 8086 micro code Ken Shirriff has just added a blog post where he analyses some of the mentioned cases:
Undocumented 8086 instructions, explained by the microcode
It ...
- 213k
9
votes
Accepted
Most modern C compilers targeting DOS 8086, running on DOS 8086 (16-bit)
I can confirm that the following C compilers work. I've also indicated the latest version of each which still runs on DOS 8086.
Borland Turbo C++ 1.01 released on 1991-02-27. The next version, 3.00 ...
- 1,445
7
votes
Tiny libc for DOS 8086
In my experiments, a void main(void) {}, compiled to a .com with @hello.lnk in the wcl arguments, OPTION ELIMINATE, VFREMOVAL inside hello.lnk, and something along the lines of -ei -obehiklnrs -ms -q -...
- 6,351
6
votes
Why are first four x86 General Purpose Registers named in such unintuitive order?
Agreeing with existing answers but being too long to shove into a comment, per a recent post on Ken Shirriff’s blog that traced the instruction set from the Datapoint 2200 through the 8008, 8080 and ...
- 36k
5
votes
Tiny libc for DOS 8086
It looks like such a tiny libc doesn't exist, and the existing full libcs (implementing most C89 functions) for DOS 8086 have too much bloat. Compared to those, the bloat of the dosmc libc is tiny, ...
- 1,445
4
votes
What is the difference between the different versions of the SID or SID86 debugger for the x86 PC that was shipped with the different DR-DOS versions?
Ok, I did a little in-depth research in the last couple of weeks. And I found this:
SID 1.0 (Concurrent DOS 3.1, Release Date 1983)
assembles and disassembles 8086 and 8087 opcodes.
supports symbolic ...
- 831
3
votes
Difference between the 8255 and 8042 PPIs
The 8255 is a PPI, the 8042 isn't, and neither is the 8288 a PPI but it is a Bus Controller which decodes the native 8088 CPU control bus signals into separate usable bus control signals to have ...
- 28.3k
3
votes
Are there multiple models of the Intel 8089 IOP?
[...] scheme of the last number being -2 on 8mhz versions -1 for 10mhz versions [...]
They are not versions but speed grades.
Versions are donated by letters after the base number.
There is no fixed ...
- 213k
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