Dude, IGN is a bunch of idiots. It doesn't take much knowledge or research to know the answer to this query here...
BUT... then again this is from the people that brought you 'Xenon - Equal to a 9GHz CPU'
The PlayStation 3's 512MB is split in half, with 256MB of GDDR3 RAM and the other 256MB in XDR. Yellow Dog can only see one of these two halves (which half, we're not sure).
BUT... then again this is from the people that brought you 'Xenon - Equal to a 9GHz CPU'