Ey up, all.

I've been rooting through some old 16 bit x86 code and I now realise I've been doing ARM for so long that x86 has become like a foreign language to me. I'm OK with the normal MOVs and arithmetic stuff but once I get into more obscure opcodes, particularly ones that assume their operands are in a certain registers, I soon end up with 50 tabs open. There seems to be little consistency in where the operands need to be instruction by instruction, maybe there's a rule I'm just not seeing? Or maybe my brain can only handle reduced instruction sets these days :)

Can anyone recommend a decent resource to get me back up to speed (it's only been 30 years)? I have a couple of train / plane journeys coming up so something downloadable would be ideal.

Thanks in advance,

BobW
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On 28 May 2025 at 04:21p, Bob Worm pondered and said...

Can anyone recommend a decent resource to get me back up to speed (it's only been 30 years)? I have a couple of train / plane journeys coming up so something downloadable would be ideal.

For 16-bit code, specifically? Bitsavers probably has a copy of
the original 8086 programmer's reference manual, which will cover
most of the instruction set. See
https://bitsavers.org/components/intel/8086/

If you're looking for something a bit more modern, then chapter
2 of volume 2A of the Intel SDM is pretty good. https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm. html

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Re: Re: (16 bit) x86 Assembler lessons?
By: tenser to Bob Worm on Thu May 29 2025 04:32:11

Hi, tenser.

For 16-bit code, specifically?

Yup, the code I'm looking at is all 16 bit DOS.

Bitsavers probably has a copy of
the original 8086 programmer's reference manual, which will cover
most of the instruction set. See https://bitsavers.org/components/intel/8086/

Yes, a quick flick through that archive very quickly turned up an overview of what each register is for and some other really useful stuff. That's exactly the kind of thing I was hoping for.

Thanks very much!

BobW
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On 28 May 2025 at 08:52p, Bob Worm pondered and said...

For 16-bit code, specifically?

Yup, the code I'm looking at is all 16 bit DOS.

Bitsavers probably has a copy of
the original 8086 programmer's reference manual, which will cover
most of the instruction set. See https://bitsavers.org/components/intel/8086/

Yes, a quick flick through that archive very quickly turned up an
overview of what each register is for and some other really useful
stuff. That's exactly the kind of thing I was hoping for.

Great! Happy to hear it.

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