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[Valentin Albillo]

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Hi, brouhaha and all,

(05-07-2023 04:35 PM)brouhaha Wrote:  The 6502 is great for some things, [...]

Such as Chess programming, for instance. See:

CPW - Chess Programming Wiki

Quoting Dan and Kathe Spracklen on the advantages of the 6502 compared to 8080/Z80 while porting Sargon: {the underlining is mine}

Danny Spracklen: Yes, the instruction set was a little more efficient, I think, and more- it was more, if you could say, RISC like. ... It was a simpler instruction set, but it actually- the cycle times on the individual instructions were very fast, like one microsecond, instead of like 4 or 5 microseconds, on the Z-80.

Kathleen Spracklen: Yes. And it had the short branch. You can’t underestimate the value that the short branch offered. They had the ability- if you could branch within a one byte distance of where you were, and using it as a sign number, positive or negative, you had an extremely fast branching instruction. So if you could make loops very, very small and tight, you could really run with high, high speed.

Also, quoting from this post in 6502.org

Right, the Z80 based machines all seem to top out at about 1500 ELO or so, despite clock speeds sometimes reaching 7.5MHz. By comparison, even the slower 6502 machines with only a 2MHz clock run at around 1700 ELO, with the later (faster) 65C02 machines starting at 1800 ELO. A difference of 300 ELO points is enough that the lower rated machine would hardly ever win (nor even draw) a game.

This is despite, in some cases, the same programmer having written the engine. So there definitely seems to have been something about the 6502 that favoured its use for chess, more than the usual difference in efficiency noted between the two.

Regards.
V.