Possible use with c128 (at c128 mode)

[odflor]

Your idea of use the pico as a Commodore ROM and in some way as a co-processor is exacly I was looking for a long time.

Mi idea is to bring new software for the c128 as cheap, and painless possible, and Your project have so much potencial por this.

There is a way to make it work on a c128 (on c128 mode)?

[cknave]

I'm not familiar with the C128, but looking at http://blog.worldofjani.com/?p=1600:

When a C128 is booted, a cartridge presence is checked. First it checks if GAME or EXROM lines are low. If this is the case, a C64 mode cartridge is connected and the machine starts in C64 mode. Otherwise the C128 memory is checked for an identifier(“CBM”) string at $8007 and $c007, this is done both for the external and internal slots.

It looks like all we'd need to do is disconnect the GAME and EXROM lines, and set the appropriate signature in the pico's RAM. For this design you'd have to physically cut the GAME and EXROM traces, but a new revision could add a jumper for it.