Exchange the CPU to another one ?

[Marten Feldtmann]

Would it be possible to remove the Z80 from the backplane and add a Z180 somehow ? Even though I'm still working on making my RC2014 running the stuff, at the end I'm looking for a Z180-system or even an eZ80 system.

[Jon Langseth]

Oh, good question, one that I haven't really considered.

A bit of semantic first, just to avoid future confusion. Let's call the LiNC80 SBC1 board with the Z80 CPU and the SIO/CTC/PIO etc, either by it's full name, or the SBC, or the main board. The word backplane should be used for a bus-board, like the Z50Bus 5-slot backplane card.

I must admit I have not spent a lot of time with the Z180, so my reply here is more or less pure speculation. I think it should be possible to remove the CPU from the main board, and place a different CPU on the Z50Bus, if care and consideration is made to make the IEI/IEO chain work. The Z180 has more signals than the Z80, and not all of them will fit on the Z50Bus, but there's room for at least four of them on the four USR signal lines. These are not tied to anything on the main board, so if they are needed to interface with RAM, or override parts of the config-register functions, they will have to be bodge-wired in (like a fix for the IEI/IEO chain). 

Considering that the Z50Bus is designed for an 8-bit CPU with a 16-bit address bus, and that the LiNC80 SBC1 is designed specifically to be a host with the CPU on board, it will probably end up being quite a hack, to be honest. I think it's a shame that Philip Stevens' YAZ180 does not have an expansion connector. If it did, it would probably be what you are looking for :)

For information about the YAZ180, see https://github.com/feilipu/yaz180 and https://www.tindie.com/products/feilipu/yaz180-pcb-modern-single-board-z80-computer/?pt=ac_prod_search

But yeah, it would be a hack that would require significant thought and wiring, but it may just be possible to create a Z180 CPU card for the Z50Bus, and remove the Z80 off the main board. People have done stuff more crazy than this before :)