PS3 XDR bandwidth?

[flec04]

Perhaps you misunderstood Shifty's comment. He just pointed out a limitation - and incidentally the same kind of limitation Cell and all other processors share, ie the performance discrepancy between processors and the memory chips they're attached to...

I understood Shiftys critique & thanked him because it was far more constructive than simply fobbing off white papers as PR!

 

[LunchBox]

Makes you wonder why neither ATI nor Nvidia chose XDR instead of GDDR4 for their next generation products...

GPU's are much better in dealing with latency than CPUs...i.e... They are much more efficient in hiding latency.

 

[ShootMyMonkey]

ok let me see if I have this right, current-gen XDR can scale upto ~102 GB/sec bandwidth correct? PS3 has 1/4th of that.

XDR2 memory scales upto 200 GB/sec or starts there, but either way, it can hit or will be able to hit 200 GB/sec. that's the least I'd expect for PS4's main memory. It's about 8 times more more bandwidth, about the same increase from PS2's main bandwidth (3.2 GB/sec) to PS3's.

AFAIK, XDR1 will only scale up to 6.4 GHz effective (which is double the rate of PS3's XDR). XDR2 doesn't really have an officially stated upper limit from what I can see, but it will apparently start at 8.0 GHz effective.

102.4 GB/sec on XDR is possible with 6.4 GHz * 128bit bus controller. XDR2 at 8.0 GHz would get you 128 GB/sec. Whether or not XDR2 scales up to 12.8 GHz effective transfer rate is yet to be seen -- it's only stated that it will scale up beyond 8.0 GHz with further process improvements. And the more difficult part of scaling up to that kind of transfer rate is to be able to wiggle voltages on the motherboard wiretraces. XDR uses a low-voltage swing (0.2 V) to handle this, but I'm slightly doubtful that such a thing will scale up to a 6.4 GHz clock signal (12.8 transfer rate).