Questions tagged [8086]
For questions specifically regarding the Intel 8086 16-bit microprocessor
63 questions
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When and why is fwait necessary when using the 8087 coprocessor?
I am writing 8086/8087 assembly code that performs floating-point operations, specifically converting numbers to scientific notation. While testing on real hardware (an IBM 5150 with a working 8087 ...
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4
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2
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449
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What's the 86 DOS system with the smallest Low Memory Area footprint?
I prepared a test program in the bigtest hg repo on our hgweb server, with a build in the download directory.
This program will try to allocate a large program memory block in the Low Memory Area, ...
- 1,583
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2
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What is the origin of the many extra mnemonics in Manx Software Systems’ 8086 assembler?
While I was viewing the file AS.EXE, I stumbled upon next list of instruction mnemonics for the 8086 processor:
ja jb jc je jg jl in jo jp js jz
aaa daa aad adc add dec bge aam jae jbe lea clc bhi ...
- 1,385
4
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1
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List of Intel 8086-compatible CPUs? [closed]
I'm looking for a good list of CPUs that are compatible with the 8086's architecture(where I can program on those CPUs the same way as I do with the 8086). I would suppose anything that starts with 80 ...
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9
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2
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How does the 8086 jump instruction work when the target address overflows?
For educational purposes, I'm developing my own software emulator for the 8086 microprocessor with VGA/MCGA support. Although it's far from complete, it's advanced enough to start using a BIOS (though ...
- 201
5
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1
answer
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8251A UART outputs unexpected data
I am currently prototyping an Intel 8088 system (Maximum Mode) on a breadboard. Later I want to move to custom designed PCB. To get some input and output, I wanted to use the 8251A chip. I have two ...
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19
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1
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What did it cost the 8086 to support unaligned access?
The Intel 8086 supported unaligned loads and stores of 16-bit data, e.g. mov ax, foo was guaranteed to work even if foo was odd.
What did this cost, in terms of performance and chip area, compared to ...
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13
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Did x86 CPU vendors like Intel, NEC, AMD, and Cyrix provide their own debugger for DOS with better CPU support and was it free?
MS-DOS's debugger DEBUG.EXE did only support the assembly/disassembly of 8086 opcodes.
DR-DOS's debugger SID86.EXE, SID.EXE and Novel's debugger DEBUG.EXE did support 80286 opcodes and more, but no ...
- 1,282
12
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1
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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?
I did a little research about Digital Research's 8086 Symbolic Instruction Debugger. Short name SID86.EXE and SID.EXE in later versions. But I couldn't find some sort of version history?
I would ...
- 1,282
0
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2
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Difference between the 8255 and 8042 PPIs
What is the big difference between the 8255 PPI and the 8042 PPI? (except that the 8255 has more IO)
Things that I spotted:
the 8042 seems to have its own clock (not using the CPU one) which seems to ...
- 315
13
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2
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Intel 80188 & 8087 clock frequency differences
Today I saw that the Intel APX-188/186 User's Manual states that you can use a 8087 as coprocessor for the 80188/186 (as the 80187 is only usable with the 186). But I was wondering about the clock ...
- 315
6
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2
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Are there multiple models of the Intel 8089 IOP?
As far as I'm concerned there is only one model of the Intel 8089 (the D8089A-3).
I am not able to find any information on this. While the 8086,8088 and 8087 use the scheme of the last number (-3 in ...
- 315
9
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0
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What should be put to the first 128 bytes of the code segment in Xenix 86?
I'm writing a hello-world program for Xenix 86 in NASM. See the full source code. If I only put this to the code segment, then it fails with segfault (Memory fault) on Xenix 286:
mov ax, 4 ; ...
- 4,241
8
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2
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Tiny libc for DOS 8086
I'm looking for a tiny libc (C runtime library) targeting small model DOS 8086, and providing (most of) the C89 library functions, including fread(...), printf(...) and scanf(...). The libc must work ...
- 4,241
33
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Most modern C compilers targeting DOS 8086, running on DOS 8086 (16-bit)
I'm looking for the most recent versions of modern C compilers which were/are targeting DOS 8086, also running on DOS 8086 (16-bit). I'm mostly interested in production-ready C compilers, rather than ...
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