I've also wondered if I should do something with a Gigatron TTL and P2, or make something just on a P2.

Emulating sound chips on the P2 is good and you can get around the issues that machines like the X16 have to work around. A lot of old sound chips don't like doing over 4 MHz.

I've heard about ...

That is neat to be able to do things like let the SRAM take up the entire address space with reserved I/O pages. The ROM could be stored on the P2 side and dumped into the external SRAM via DMA before the 6502 is allowed to start. I guess all sorts of interesting things could be done, like even cold ...

Nice reply. Thanks.

I was thinking, one thing that was nice about retro computers was that they came with BASIC in ROM. I was thinking, BASIC could be incorporated on the P2 side since the peripherals are there, but that begs a new question. What would be the role of the 6502 if the P2 did the ...

Good point. Well, even the P2 CORDIC solvers are good enough to use alongside a 6502. If you run the P2 at 22-24 times the 6502, then it would take 3 6502 cycles to do the 54 P2 cycles needed. And if you clock the 6502 at vintage speeds, you could do it in a single 6502 cycle. And whatever overhead.

Thank you, Ed. I'm still not sure if I want to build anything at all. I just lost the interest I once had. And in this project idea, is there really a need to have a separate 6502? I mean, the P2 can emulate one just fine, and sticking within healthy overclocking ranges, the P2 can emulate a 14 MHz ...

I wasn't asking about shared video RAM. See, the P2 hub should work just fine for video RAM. It is an inherent feature of the P2. The hub RAM will be the slowest, but that shouldn't be a problem at the resolutions I'd be interested in.

The idea is to passively read the SRAM on the board. It seems ...

I'm thinking I'd like to have a machine that uses the 65C02, preferably at 14 MHz if possible, uses SRAM, and has a Propeller 2 attached. It seems this would help keep the total chip count down. The advantages would be not needing VIAs, not having the headaches of various sound chips that won't like ...

What about detecting a Sally 6502? I imagine it would test as a stock 6502 since MOS made it for Atari. Really, that just adds back a feature that MOS removed since the original die left room for multiplexers to take the 6502 off the bus. That also explains one of the NC pins. I guess they didn't ...

Apparently, I was misunderstood. I didn't mean to make it sound like I was saying the 'C02 added any undocumented instructions, just instructions.

And if you can use the data bits for address bits, that counts as part of the bus.

And as for "theoretical," that is a reference to the boards using ...

What would be interesting would be an FPGA that has all the 6502 variants in one place and a system built around that. They each have their advantages.

The original is the most known and most compatible with older software.

The 6507 is the cut-down version used in the Atari 2600, and if you were ...

For the 65C816, I'd be more interested in a version that has demuxed addresses. I've read that WDC may make FPGA cores like this available. It would have been interesting if Stefany had used such a modified '816 on her Foenix, and preferably one that boots into the native mode. That way, the board ...

If there isn't enough RAM in the FPGA, external RAM is required, and external RAM
probably would be slower than the CPU, so "CPU cache" might become a topic...
a topic where I'm having little to no knowledge.

If nothing else, someone could do it in a hybrid fashion. You'd need to code in ...

Thanks. It sounds like a scope is certainly necessary to make sure.

And I imagine also if one is doing this for Atari, it would likely be more stable on the SRAM clone machines. That is just in case the timings are a little off, there won't be any refresh problems. Converting one of those machines ...

I do wonder if there is a way to keep the default behavior the original way but get the halt line to enable the newer behavior as needed.

Yeah, I think that is how some manage to get the 65816 to work. I think that only takes 2 chips to get the halt signal from the board to those 2 lines and maybe convert a few other signals.

Now, an issue with going to 6502C is that you may lose some undocumented instructions. A lot of vintage ...