I wish I had time to play with these! But maybe someone else will.

Great Plains Electronics is a small supplier I learned of only recently. Hidden on their "clearance" page ( here ) are several chips from the Transputer family, including 25MHz CPUs and FPUs. (A few other interesting tidbits, too.)

I have no association with GPE but in the interest of anycpu forumites I thought I'd pass this along.

-- Jeff

Nice find!

IMST805-G25S Transputer, 25MHz, Floating Point, $15
IMST425-G25S Transputer, 25MHz $10.00
IMSC011-P20S Transputer Link Adapter $5.00
IMSC012-P20S Transputer Link Adapter $5.00
IMSC004-G20S Transputer Link Switch $10.00

Just to clarify, both the 805 and 425 are transputers, with CPU, 4k byte onchip RAM and four communication links and a 32 bit wide DRAM-compatible memory interface. The 805 also has an FPU but the 425 doesn't.

As the transputer has a handy pre-boot protocol, you need only a 5MHz clock input and a bypass capacitor. To talk to it, you need to speak transputer link protocol, which is pretty simple but not the usual serial. It runs at a fixed 10 Mbit/s rate, so to bit-bang it you need a deterministic machine.
http://www.transputer.net/tn/18/tn18.html

This is where one or other of the link adapters should be handy - I think the C012 interfaces transputer links to an 8 bit bus, whereas the C011 gives the transputer an 8 bit parallel port.

(Or, use an external boot ROM instead of trying to boot over the link.)

See also
http://www.transputer.net/fbooks/fbooks.asp
and
http://www.transputer.net/tn/tn.asp

I have a whole bunch of transputers, and one day perhaps might try to wake one up.