Some interesting photos of an R680 prototype have appeared on ChipHell. You may recall this card has two RV670s which we already find on Radeon HD 3800s.
Besides the absence of memory chips (it will be equipped with GDDR4 0.7 ns, or in other words a frequency of around 1400 MHz) we can see the presence of a PLX PEX8547 chip.
Described by its creator as a PCI-Express switch controlling 48 lanes shared between 3 ports, this should therefore allow GPUs to inter-communicate as well as with the Northbridge.
It’s slightly surprising that the
switch conforms to the PCI Express Base Specification, rev 1.1 while the RV670 supports the PCI-E 2.0 standard. Given this is a prototype, there should be nothing to worry about at this point. We will just have to see if AMD can wait for the release of an adequate switch (PEX8647?) in order that its card isn’t affected by any hardware limitation. Finally, while there is no mention of a PEX8647 on
PLX site, there is indeed such a
product!
