Ran across this on eBay, pretty sure it'd run any arcade game at full speed. 
Not even close.
1) 600MHz Alpha processors are good, but MAME is still MHz bound. You're looking at Pentium3 1GHz performance levels at absolute best, depending on the game. To put it into perspective, Alpha processors give roughly the same performance as POWER processors (both are 64bit RISC CPUs with tonnes of cache), which are the big brother of PowerPC CPUs found in Apple Macs. How well does a 600MHz Mac perform in MAME?
2) MAME does not benefit from parallelisation. The only MAME port that I know if that is multithreaded is AdvanceMAME, and even it only sees 1-2% boosts via things like screen rendering and sound calc offloads rather than actual emulation speedups.
Sorry to burst the bubble there. Cray computers are VERY task specific. That machine you linked to would even run Microsoft Word slower than your desktop PC would, simply because it's designed for a very different task.
