Hi!

I have been looking through the different 16-bit versions of the 6502 (or the effort to make such), but I still haven't found anyone trying for complete 65816 compatibility. Is there such a thing out there? I know about the VeriSNES and the official WDC softcore, but the first is unavailable and the second is too expensive.

Typically! After posting this, I found the MiSTer SNES which has a 65C816 core in VHDL:

https://github.com/MiSTer-devel/SNES_MiSTer/tree/master/src/65C816

Which is a port of the Japanese original:
https://github.com/srg320/FpgaSnes/tree/master/FPGA/65C816

(his web page is here, but in japanese)

Good find, and something to keep an eye on. I see 1000+ lines of microcode, and I see a recent update tweaking a dozen of those lines.

As has been noted before, a testsuite can work wonders, but it's a lot of work to put together.

That is true. But it does run SNES code.. which was based on the original WDC? Or was it a modified core?

I think the SNES core isn't modified - it seems that MESS uses the same code to emulate the SNES and the IIgs.
https://github.com/mamedev/mame/blob/ma ... g65816.cpp

(There is SNES-specific modelling of the memory banking and the multiply/divide widget and the bus timing, I think, but those are not differences in the core.)

Have you tried the FT816 core? It's not 100% cycle compatible, but it's close, It's been used successfully in this project:
http://atariage.com/forums/topic/277736 ... s-a-65816/

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