I posted an update to the MCL64 project: https://microcorelabs.wordpress.com/2021/11/29/mcl64-update/
It appears that a number of Commodore 64 games rely on a few of the unstable undocumented opcodes, so I updated the code to support them.
Hmm -- I thought the C64 also allows the video memory ...

Nice idea! You are using the USB CDC serial port, right? So no extra hardware is needed, neat.

In response to the recent wave of writeups on the 65F02, I have received a couple of questions whether the board could also be used as an in-circuit tester. Your Teensy platform seems much better suited ...

In my understanding the pullup resistors are only required when you want to use the MockA65xx (or the GODIL, for that matter) in CMOS-based host computers which have their switching threshold at 2.5V. In those environments the 3.xV high output level of the '3861 chips is probably marginal, but in ...

Thank you for sharing! And you are using the MAX10, which I found tempting but had not seen in hobbyist use. Are you happy with the chip and with the development tools?

Your level converter solution is closer to the original GODIL, with pullups on every pin. The NXB0108 level converters which I am ...

In some of the applications I have in mind -- e.g. accelerating old chess computers -- space can be very constrained, both laterally and with respect to height. So I would prefer to stay within the DIP socket's footprint, and ideally not add height beyond a regular IC.

(With the 65F02 the latter ...

Great suggestions, Ed and Dave! Especially since you mentioned exactly those FPGAs which I have also been pondering. 8)

The package is an important constraint for me. It needs to fit between the DIP pin rows, i.e. can't be wider than 13 mm. A BGA seems unavoidable, but 0.8 mm pitch (maybe 0.65 mm ...

As a sideline of my explorations of a better 6502 accelerator, I have been wondering whether it makes sense to try and develop a successor to the venerable GODIL board: a plug-in board in 40 and/or 48-pin DIP format with a smallish FPGA, bi-directional 5V level converters on all pins, and jumpers to ...

Thanks, Dominic. Well, laying claim to performance improvements of your code is at least three steps away for me, I guess...

Just received my Teensy 4.1. I will probably start with some simple timing experiments using embedded assembler in the Arduino environment -- with all the caching ...

I would be more optimistic regarding the performance. If you look at dp11's post earlier in this thread, he mentions an emulated 6502 clock of 1/4 the emulator clock for his Pi Pico (RP2040) emulator.

That's for a tightly optimized emulator where the core parts are written in assembler, running on ...

Alright, here is quick clip of "Brian's Theme", the 1979 Apple II demo, being loaded from disk and run with the 65F02 in the CPU socket. For comparison, here is the original speed on a 1 MHz Apple II (someone else's video).

As stated before, the acceleration factor is >50 even with the graphics ...

It's not pleasant to look at, flickering at 3 Hz. ;-)

I need to get the 65F02 configured for the Apple again; it's in a chess computer now. (I split the VHDL into two separate configurations, since the routing paths were getting congested in the logic which monitors the address pattern for the ...

Thanks, Ted. Brian's Theme will of course access the video RAM quite a bit. (Although the effect is not too bad. With the 65F02 I found that, when mirroring the video RAM on-chip so that reads from the video RAM are fast, I still get more than 50x acceleration on Brian's Theme , compared to the "raw ...

Yes, when not running cycle-accurate the acceleration is for code execution and not for the I/O's. How fast does the MCL65+ run for purely internal code execution? Say, just a loop with many iterations in BASIC, with some computations but no I/O?
Ted, would you have a data point on the above? When ...

I've just remembered one of the observations about the teensy vs the pico: the teensy's pinout, in the versions we looked at, don't make it easy to drive or sample say a 16 bit bus in one go. There's more shifting and masking than would be ideal. That said, with a 600MHz processor overclockable to ...

[...] The performance-critical aspects are, I think:
- dispatch
- dealing with emulation of interrupts
- detection of special vs ordinary accesses
- doing the work of the opcode
[...]

Thanks for pointing out the interrupt and external access hurdles, Ed.

To discriminate external (I/O incl ...