On the feasibility of PPC for Minimig/Fpgaarcade etc.

[Iggy]

I'm sure that was once said about 68K or any other CPU softcore at one time.

What would be the point? Why not? For those decrying it as a sane business proposition, that's one thing. But some involved with such things like Minimig are doing it more to learn how and/or have fun than anything else.

There's a slight difference between emulating a 50Mhz processor and a processor like the one I have in my Powermac (which at 1.8Ghz runs 36 times faster).

No current FPGA (or any that's likely to be introduced soon) operates fast enough to emulate processors running at that speed.

[fishy_fiz]

I just dont see the point to it (at least as far as something like minimig is concerned). Firstly speed of the cloned ppc wouldnt differ greatly to that of a 68k cpu using fpga, and secondly, as most people who have/had one will tell you ppc without rtg is a huge waste of money. Even with RTG I constantly questioned my bppc purcahse. There's maybe a dozen pieces of software that are worth the effort, and those exist for 68k anyway (with the exception of warpsnes,mess, shogo, Heretic2, and Wipeout2097(although most of these are open source anyway)), so given the same speed the ppc side is redundant. The only exceptions to this rule are MOS and OS4, which would both be waaay to slow (even things like Sam and Efika are too slow for things that purport to be modern oses) on an fpga based ppc core.
So, technically yes it can be done, I just dont see a point when it comes to amiga stuff.

[billt]

(I recall the only available m68k has an incompatible instruction "MOVE sr,")

The "only available m68k"? There's a few of them on opencores alone.
http://opencores.org/project,tg68
http://opencores.org/websvn,listing,k68
http://opencores.org/project,ao68000 (which I'd like to see happen in minimig)
http://experiment-s.de/en/atari-ste-in-a-chip/

Besides, they're open-source. Fix it.

[joemango]

There's a slight difference between emulating a 50Mhz processor and a processor like the one I have in my Powermac (which at 1.8Ghz runs 36 times faster).

No current FPGA (or any that's likely to be introduced soon) operates fast enough to emulate processors running at that speed.

Hear hear.  Any PPC emulator implemented in an FPGA is probably going to run slower than the cheapest current PPC part you can find out there.  Better to put a daughterboard on the replay with a real ppc that doesnt suck up as much power or system resources on the FPGA which is there to emulate chips you CANT get super cheap (or at all).

Yeah, it's probably a good idea to start a PPC core in vhdl, but it wont be really needed for a good while to come.

I say make a pci-e interface daughterboard for replay so you can plug it into an amigaone board and use it for all the classic stuff.

[billt]

I say make a pci-e interface daughterboard for replay so you can plug it into an amigaone board and use it for all the classic stuff.

Does Replay have PCI-Express capability? There are some FPGAs capable of such a connection, but I don't know if the one chosen for this board is one of those or not, or if any connection area was laid out on the board with that kind of signalling in mind. I'd have suggested much the same thing but via PCI32 if there's enough expansion pins available.

[freqmax]

billt, Minimig uses a physical m68k chip. With a softcore you can correct anything at will.

Minimig has some constraints regarding volts, physcal package etc.. so it's slightly picky about what chip can be used asfair.

[billt]

billt, Minimig uses a physical m68k chip. With a softcore you can correct anything at will.

Minimig has some constraints regarding volts, physcal package etc.. so it's slightly picky about what chip can be used asfair.

Ah, sorry. I have a DE1 board and forget the original board had a hard CPU chip. I think of Minimig as all-internal to FPGA SoC design, not as a particular PCB. I'll try to remember that part.

[freqmax]

@Iggy, The point is to be compatible with the classic accelerators. Few them ever came near any 1000 MHz ranges