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http://www.e-basteln.de/computing/65f02/65f02/
The 6502 was the CPU in my first computer (an Apple II plus), as well as many other popular home computers of the late 1970s and 80s. It lived on well into the 1990s in game consoles and chess computers, mostly in its updated “65C02” CMOS version. Here’s a re-implementation of the 65C02 in an FPGA, in a pin-compatible format that lets you upgrade those old computers and games to 100 MHz clock rate!
The concept
The idea of implementing a CPU core inside an FPGA is not new, of course. In fact, the CPU core I am using is not my own, but was developed as a 6502 core by Arlet Ottens, and extended to cover the 65C02 opcodes by Ed Spittles and David Banks. A big thank-you to Arlet, Ed, and Dave for developing the core and sharing it freely! Links to their original work are on the Files & Links page.
(Score: 3, Interesting) by KritonK on Thursday October 14 2021, @08:27AM (1 child)
A long time ago, in a galaxy far far away, my main computer was a BBC Micro, which had a 6502 running at 2 MHz.
I liked to fiddle with its hardware, and one upgrade I tried was to replace the stock 6502 with a 65C02. The first thing I tried after the upgrade was to run a game I used to play at the time. The result was jerky movement and flickering, as the game had been timed exactly to the instruction timing of the stock 6502. Needless to say, I switched back to the original 7602.
If this was the result from small variations in instruction timing at 2 MHz, I shudder to think what would happen not only with a different implementation of the CPU, but with 50-fold increase in clock frequency as well.
As for performing calculations with this new CPU, I would think that one would have moved to even more powerful CPUs a long time ago, to perform said calculations. I guess this is a niche product for exactly the kind of use they envisioned, i.e., upgrading 80s style chess machines which, presumably, would benefit from a much faster CPU, as they would be able to search more positions in a given amount of time, assuming they don't run out of memory or encounter other bugs, due to the increased number of calculations.
(Score: 4, Interesting) by looorg on Thursday October 14 2021, @10:53AM
This would be my main concern with this upgrade to. You could probably write, or rewrite, new software for it that would be more or less fine. But a lot of old software will or could probably act very weird. The main issue here is timing, or various tricks used to time and delay things now being performed so much faster. Some games could more or less be press f1 to start and the next thing you see if the game over screen as things have just flown past and across the screen. So there pretty much needs to be some kind of choke that you can use that forces things down to the old normal speed when and if needed.
From reading the site tho as you note it seems to them that the primary usage here is for old chess machines. For them I assume things will just be fine, since it should mainly be about then calculating the tree-graph of possible moves and pick the best one and if that becomes faster then less wait time for you.
That said if it works fine, or can be tweaked for the other codes and be made compliant with say 6510 as he mentions, and you could get say a 100 MHz C64 running cheaply that could also have it's fun. But as noted it could break more then it fixes.