"Mike" <mikee@mikee.ath.cx> wrote in message
news:qxzxf.161$M95.105@fe04.lga...
> What's the difference between a p550 and a p550Q?

The "Q" means Quad core, so in either of the processor slots you can put 4
processor cores (on the same die).
So you can put 8 cores into a 4RU box, which is a pretty impressive density.
The cores run at 1.5GHz so are
clocked a fair bit slower than the fastest dual core CPUs (1.9GHz for the
Power5+).
Not sure why IBM have this on the "Entry Level Systems" page though. It's
certainly not an entry level device.