It\'s only the modules that have been halved from 512Mbit to 256Mbit (i.e. from 64MB modules to 32MB). Why they\'ve chosen this direction is still not clear (some people are speculating on doubling of bandwidth from 25 to 50 GB/s, see beyond3d.com forums), there has been no mention of overall XDR RAM reduction since they haven\'t even told anyone how much they were going to put in it to begin with.
If you\'ve heard them actually say they were planning on having 512MB XDR RAM in it, Knotter8, then I\'d like a link to the source because that\'s the first time I\'ve heard of it.