Interesting. Note that the 800MHz 750FX has been reported to run quite stable at 933 with the VGA type cooler used in the A1G3-XE (voids warranty etc, and I don't even have one myself to test it on).
But it doesn't work at 1GHz (with that cooler), and it's producing a lot more heat than the estimated numbers IBM originally gave out for the 1GHz version.
I've been waiting for this GX for some time now (I read the same comment in a pdf on IBM last year as some others seems to have done). If "the reg" is right about 1MB L2 cache, we have a winner :-)
The 750FX is already better at multiprocessing than the previous versions, I think. But might still be room for improvements.