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The KK Computer: A Radical 6502 Redesign (laughtonelectronics.com)
100 points by ingve 9 months ago | hide | past | web | favorite | 8 comments

Thanks for posting, ingve (and 0x12). 0x12's HN thread [1] about my project included the following TLDR:

"Guy expands 6502 to 16M address space by intercepting the databus and re-mapping unused opcodes and clever use of the spurious signals generated by the cpu when executing other undefined opcodes, adds a few registers to make the whole thing transparent from an assembler programmers point of view. In other words, there is no difference to the programmer between native and newly minted instructions.

On top of that he boosts the speed of his forth interpreter by concentrating on a frequently used construct called 'NEXT' in a way that should make anybody that has tried to optimize the inner loop of some VM or language proud. After all, what better way to optimize in such a situation than to be able to mold the instruction set to your desire.

He then uses this home-brew Frankenstein contraption as his benchtop computer for multiple years to do real work (instead of just shooting some pretty pictures and calling it a day)."


HN folk may recall a project much less ambitious than the KK Computer which, for some reason, attracted far more online attention!

One-bit Computing at 60 Hertz [2]



Regardless of its quirks, I loved the 6502 when I was writing my revision of the onboard ROMs. Easy to get the scope of the instruction set, etc. Having this set of expanded capability would have been game changing... maybe a riff off GEOS, or writing an Echelon clone with Minecraft size worldmap...

The mind boggles, and wonders if I just started my retirement project planning.

Man, I just wish teenaged me had had access to a KK...

I wonder if there'd be any practical use of this enhanced 6502 in the modern world? Implemented in VHDL/Verilog perhaps?

Western Design Center already sells the 6502/65816 core IP. The 816 already provides a 24 bit address space. It's apparently in more things than you'd guess, they are making enough money to stay in business, anyways. No new IP it seems, but continuing to manufacture the old.

Well his excellent write-up acknowledges the WDC 65816 which was you can still buy (IC or Verilog), so I guess somebody wants it?


I had a BBC Micro B (a very British computer for those that haven't heard of it) and really wish I'd had this. Sideways ROM/RAM banks just didn't cut it.

I really really doubt it. "Because it's cool" seems to be the only reason / motivation.

Back in the day (late 1980's) there was ample motivation as I had no knowledge of or access to the 65816. Programmable logic has changed the landscape since then -- and btw I have whimsically contemplated a modern re-issue of the KK. (I've also contemplated some KK-ish hacks that would yield an improved 65816!) But I agree the scope for practical application has shrunken. In the first place you'd need to be committed to the 65xx family, because alternative, modern processors offer compelling advantages not featured by 65xx.

That said, KK has features not present on the 65816, and in certain applications these could be pivotal. Obvious examples include the NEXT instruction and the new addressing mode. Less obviously, KK preserves the 65C02's bit-manipulation instructions, which can be a boon in I/O-intensive code. The '816 sacrificed these opcodes to make room for alternative, also-worthy objectives.

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