I got a bit curious if it's possible to implement PPC in FPGA..

The simplest PowerPC processor Power1 uses 2,04 million transistors for logic, and 4,86 million for memory. The key is the logic gates.

Given that MC68000 has 40 000 transistors. And MC68020 uses   190 000 transistors.

The Spartan-3E 1200 used has 19 512 logic cells of which the MC68000 implementation uses 20 %. Which translates into 3902 logic cells. Which should mean that 199 022 logic cells are required. So a Virtex-5 chip like XC6VLX240T should be able to handle the task.

Maximum logic cells:
Spartan-3 33 192 logic cells.
Spartan-6 147 443 logic cells.
Virtex-6 566 784 logic cells (XC6VHX565T).
Virtex-7 2000 000 logic cells (not released yet!).

So the XC6VLX240T will likely make it possible to implement a PPC accelerator
The catch is that the free version of the programming software ISE likely won't support it. Otoh one can combine multiple chips.

So the XC6VLX240T will likely make it possible to implement a PPC accelerator
The catch is that the free version of the programming software ISE likely won't support it. Otoh one can combine multiple chips.

The best price I can find for the XC6VLX240T is $1412.40.

Not really a good idea.

You can get a XC5VFX30T, which has a PPC 440 cpu built in for about $450.

It might be possible, though unlikely to be cost effective as long as new PPC designs are still being produced. For 68k, it's still not a given that it's even cost effective to compete with a 68060 this way (we'll see how the Natami plays out), but in that case time is on the side of FPGA's - that's not the case for PPC.

Disclaimer - I know next to nothing about FPGAs.

I don't see why you would need a huge FPGA to emulate a PowerPC. The instruction set shouldn't be harder to implement I'd think (after all, PowerPC is supposedly RISC). I think all those extra transistors are in the PowerPC because its a more modern, powerful chip than a 680x0. Those extra transistors are doing things like implementing multiple units and stuff. A modern Intel CPU shares the same core instruction set as a 386 but obviously use far more transistors.

Anyway, I do think a PowerPC in FPGA would be a bit silly unless there is some great need to run PowerPC code. Whether you implement 680x0 ISA or PowerPC ISA you are probably going to get about the same performance on a given FPGA. The only advantage I see to PowerPC is that modern variants of the ISA would include SIMD, which might help the FPGA state instructions to the CPU in a way that helps it process data more efficiently.

The thing about HDL-code is that once you have it, the supply is secured. Speed might suffer but you can run things. And as time progresses FPGA gets faster and cheaper while chips might be EOL'd. Though currently FPGA implementation would not be cost effective.

How is compatibility between classic PPC accelerators and currently manufacturered PPC chips?
(I recall the only available m68k has an incompatible instruction "MOVE sr,")

The thing about HDL-code is that once you have it, the supply is secured. Speed might suffer but you can run things. And as time progresses FPGA gets faster and cheaper while chips might be EOL'd. Though currently FPGA implementation would not be cost effective.

How is compatibility between classic PPC accelerators and currently manufacturered PPC chips?
(I recall the only available m68k has an incompatible instruction "MOVE sr,")

I think you confuse PPC and coldfire... Not to mention I have no idea what you are trying to achieve... A PPC on an FPGA would be painfully slow

Virtex-5 FXT
I've looked at the price some time ago and they were too expensive at that time. I don't think PPC cores are integrated in the Virtex-6 Xilinx FPGAs anymore.

greets,
Staf.

I'd never noticed that before. An FPGA with up to two 440 cores. Pretty slick.
It would require a LOT of work, but that could be used.

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.