MiniMig EAGLE schematic & flying board

[boing4000]

Nice idea but don´t forget that the Minimig has an asynchronous external bus. Insinde the FPGA the RAM and CPU are handled synchronous to the "Amiga chipset". An external Gayle chip would run at far more speed then the internal Amiga (zorro) bus. Even the CPU do not hold by signal as the real 68000 in any Amiga is doing. Also the S-RAM is working at aprox. 50-60ns (depending on the chips and core settings), that is much faster then in a real Amiga.

Best would be to code an Gayle chip inside the FPGA and let it control the timing. There are a few unused lines available on the chip. Or construct a new board with special IDE connector and hardwired line to the FPGA as the DEx Boards do.

Also its possible to simulate a harddrive via hardfile on SD-Card. Unfortunately I dont have any luck in compiling the PIC C-sources. If I would, even adf write support could work just now.

[boing4000]

wolfchild wrote:
So, this means that one cannot add memory mapped peripherals directly to the 68k?  You know, the kind that piggy backed to the socketed CPU on the old Amigas...

Of course, I'm considering issues as 3.3V and actually connecting to the MiniMig's 68k as 'solved' for the scope of this question.

Regards,
Edwin

As in my understanding out of Denis's posts and the comments in the source code it is not possible that way as in a real Amiga. The external bus of the Spartan fpga is splitted into RAM and CPU part. The CPU is working nearly the same as in a real Amiga (7/14MHz) but as mentioned it is not in sync and the _hold line is combined with _reset line on the PCB. The CPU is always operating (even if chipram is adressed or DMA is active) and inside the fpga all signals are buffered and resynced with the actually chipset.

The S-RAM is indeed operating at very high speed and one can not simply add some D-RAM. Adding comparable S-RAM chips would work, only an additional adressing line has to be used (there are sill some free fpga lines).

So we are in an fpga environment and need to think of "hardware inside a chip" to create functions and "pluggung" additional Amiga hardware to the "programmed system".
Outside the fpga it is really another world running :-)