There is huge potential in pico.
- it IS 5V tolerant, just not 5.5V 😀 and not on all pins. So with some careful planning it should be possible to design simple cards with no level translator chips, just PCB and $1 RP2040
- IO coprocessors should be fast enough to bitbang ISA (8MHz ISA bus 125ns cycle time). Main limitation is size of ram and no compare instruction 😀 so anything more complicated needs to be DMAed to ARM core, computed there and send back. pico pio in() out() push() pull() mov() irq() wait() jmp() set() https://tutoduino.fr/en/pio-rp2040-en/ https://github.com/soundpaint/rp2040pio

Example emulated ROMcart for N64 https://github.com/kbeckmann/PicoCart64 https://github.com/kbeckmann/PicoCart64/blob/ … test/cic_test.c
Time between ~N64_READ and bit output on AD0
With constant data fetched from C-code (no memory access)
--------------------------------------
133 MHz: 240 ns
150 MHz: 230 ns
200 MHz: 230 ns
250 MHz: 190 ns

With uncached data from external flash
--------------------------------------
133 MHz: 780 ns
150 MHz: 640 ns
200 MHz: 480 ns
250 MHz: 390 ns

This sort of thing is already being done, look up the PicoGUS and PicoMEM.
What would be really nice is if someone used this extremely cheap MCU to make an optical drive emulator, instead of the overpriced >$300 options that are currently available.

rasz_pl wrote on 2023-05-01, 21:20:

There is huge potential in pico.
- it IS 5V tolerant, just not 5.5V 😀 and not on all pins. So with some careful planning it should be possible to design simple cards with no level translator chips, just PCB and $1 RP2040
- IO coprocessors should be fast enough to bitbang ISA (8MHz ISA bus 125ns cycle time). Main limitation is size of ram and no compare instruction 😀 so anything more complicated needs to be DMAed to ARM core, computed there and send back. pico pio in() out() push() pull() mov() irq() wait() jmp() set() https://tutoduino.fr/en/pio-rp2040-en/ https://github.com/soundpaint/rp2040pio

Hi,

It is impossible to not use multiplexing component due to the low number of pins.

Then, the multiplexing does the level shifting: it is more safe.
In my PicoMEM Board, the multiplexing login need one inverter, so I used the other inverter pins for level shift.
This also help because the PC Mainboard main consume some current the Pico can't deliver... (The bus is Bidirectionnal....)

Then, to have the Pico Safe, and lower its power consumption, it is highly recommended 😀

My Board does not use DMA as well, it is not needed due to the nature of the ISA BUS: It is not a simple memory interface with one read and write signal like for other projects...
To "Remove" the memory size problem, I added a PSRAM to the board (8Mb). This add wait states, but it can be improved with DMA (I still need to have it working, I have a little problem with it)

This ISABlaster is really basic and my Board and others already does much more since some months 😀

I don't understand much about this, but I think an ideal world would be a card that connects via riser to several ISA slots (or PCI32) and this card emulates several solutions, such as cd drives, floppy disk, hd, sound card , network, ps/2. It would be like a compatibility filter between modernity and retro. I'm afraid the costs would be high for such a complex emulation, but the costs can be amortized with demand, if many people are interested in funding a gofundme project or something like that, I think it would be feasible.

The little experience I had with things like that was creating an external emulator/synthesizer using the underside of a lenovo core2duo laptop to process VSTs, with midi inputs and outputs. The result was excellent.

Offtopic: I particularly HATE floppy disk emulators, they ruin the look, and it sucks having to choose floppy images using just that numeric display, this gave me the idea to build my own, using a real floppy drive whose head reading was replaced by a MicroSD reader, and a floppy disk with an internal microSD, and a 2" screen to choose the image to be mounted (a common and cheap display, used in Chinese MP4 players) but that during idle mode, displays a "66Mhz segment display" .

A card wouldn't need to connect to several slots; they're all part of a bus, the signal lines are connected in parallel.

The "easy" way to emulate a floppy drive is by emulating the controller itself rather than the drive.

jmarsh wrote on 2023-06-01, 04:18:

The "easy" way to emulate a floppy drive is by emulating the controller itself rather than the drive.

in case of floppy the easy way is emulating drive because there already are working open source implementations https://github.com/keirf/FlashFloppy

Disagree, because in that case you still need a separate floppy controller which defeats the purpose of the proposed "all in one" card. And that code is hardly portable to generic hardware...

Its just one example, there are more implementations for more platforms. http://amigadrive.blogspot.com interface is very simple, just ~11 gpios with very relaxed timings.