4 ms·

:You’re thinking of A86: https://en.m.wikipedia.org/wiki/A86_(software) https://en.m.wikipedia.org/wiki/A86_(software)

astrobe_ 6y ago
I can confirm. The author was an Intel engineer who was dissatisfied with how his senior engineers did the DOS EXE format in the intro of the docs of his assembler. A86/D86 where fantastic, with extra bonus points for the docs.
weinzierl 6y ago
It's been so long that I read that remark in the manual and I'm glad I wasn't just imagining it;-)
userbinator 6y ago
Decades ago, I remember figuring out quite a bit of that, and here are my original notes from that, including tables that show the pattern clearly: MOV rA, rB: B: AL AH BL BH CL CH DL DH A: 1 1 0 0 1 1 0 0 AL 1 ** ** 8A 8A ** ** 8A 8A AH 1 ** ** 8A 8A ** ** 8A 8A BL 0 8A 8A ** ** 8A 8A ** ** BH 0 8A 8A ** ** 8A 8A ** ** CL 1 ** ** 8A 8A ** ** 8A 8A CH 1 ** ** 8A 8A ** ** 8A 8A DL 0 8A 8A ** ** 8A 8A ** ** DH 0 8A 8A ** ** 8A 8A ** ** * = "reversed" opcode (88) MOV rA, rB ( word regs ): B: AX BX CX DX SP BP SI DI A: 1 0 1 0 1 1 0 0 AX 1 ** 8B ** 8B ** ** 8B 8B BX 0 8B ** 8B ** 8B 8B ** ** CX 1 ** 8B ** 8B ** ** 8B 8B DX 0 8B ** 8B ** 8B 8B ** ** SP 1 ** 8B ** 8B ** ** 8B 8B BP 1 ** 8B ** 8B ** ** 8B 8B SI 0 8B ** 8B ** 8B 8B ** ** DI 0 8B ** 8B ** 8B 8B ** ** * = "reversed" opcode (89) The above tables apply for the following two-operand instructions: ADD OR ADC SBB AND SUB XOR CMP For TEST and XCHG, which are commutative, A86 always puts the first operand in the r/m field if possible, while MASM puts it in the reg field if the first operand is a register.
- weinzierl 6y ago
  Wow! Back then, I was not quite sure if they had really implemented it or if they just claimed they had to encourage people to pay. I would never have imagined that I'd get an answer to that question a quarter of a century later. Thanks for the comment!

I can confirm. The author was an Intel engineer who was dissatisfied with how his senior engineers did the DOS EXE format in the intro of the docs of his assembler. A86/D86 where fantastic, with extra bonus points for the docs.

weinzierl 6y ago

It's been so long that I read that remark in the manual and I'm glad I wasn't just imagining it;-)

userbinator 6y ago

Decades ago, I remember figuring out quite a bit of that, and here are my original notes from that, including tables that show the pattern clearly: MOV rA, rB: B: AL AH BL BH CL CH DL DH A: 1 1 0 0 1 1 0 0 AL 1 ** ** 8A 8A ** ** 8A 8A AH 1 ** ** 8A 8A ** ** 8A 8A BL 0 8A 8A ** ** 8A 8A ** ** BH 0 8A 8A ** ** 8A 8A ** ** CL 1 ** ** 8A 8A ** ** 8A 8A CH 1 ** ** 8A 8A ** ** 8A 8A DL 0 8A 8A ** ** 8A 8A ** ** DH 0 8A 8A ** ** 8A 8A ** ** * = "reversed" opcode (88) MOV rA, rB ( word regs ): B: AX BX CX DX SP BP SI DI A: 1 0 1 0 1 1 0 0 AX 1 ** 8B ** 8B ** ** 8B 8B BX 0 8B ** 8B ** 8B 8B ** ** CX 1 ** 8B ** 8B ** ** 8B 8B DX 0 8B ** 8B ** 8B 8B ** ** SP 1 ** 8B ** 8B ** ** 8B 8B BP 1 ** 8B ** 8B ** ** 8B 8B SI 0 8B ** 8B ** 8B 8B ** ** DI 0 8B ** 8B ** 8B 8B ** ** * = "reversed" opcode (89) The above tables apply for the following two-operand instructions: ADD OR ADC SBB AND SUB XOR CMP For TEST and XCHG, which are commutative, A86 always puts the first operand in the r/m field if possible, while MASM puts it in the reg field if the first operand is a register.

weinzierl 6y ago
Wow! Back then, I was not quite sure if they had really implemented it or if they just claimed they had to encourage people to pay. I would never have imagined that I'd get an answer to that question a quarter of a century later. Thanks for the comment!