PCIe 2.0 vs 3.0, and their requirements for utilization

Tig2575

Distinguished
Jan 31, 2012
28
0
18,540
Hey all, I'm not sure if I've posted this thread in the exact right category, since the topic (from what I've been able to read) seems to cross multiple disciplines.

I've read that the Radeon 7900 series is the first graphics card compatible with PCIe 3.0, and I know that there are mobo's out already that include PCIe 3.0 slots, but I've also heard people say that "you can't utilize PCIe 3.0 without an Ivy Bridge processor"

Is that true? Does the utilization of a specific version of the PCIe bus depend on both the CPU and GPU being compatible with that particular PCIe version? If so, can someone explain the reasoning behind that? My understanding of computer architecture is probably considered limited compared to many of the experts on this forum, but I figured that if the PCIe 3.0 bus is feeding into the southbridge, it wouldn't matter what CPU you have, because that information would then be carried to the CPU from the southbridge via the internal bus, not via the PCIe 3.0 bus.

All the best,
Tig
 
Well currently, the controllers are built on to the board. However even the highest end radeon 7970 can't fully utilize (saturate) the older pcie 2.0 slot. Just pick up a z68 board with pcie 3.0 and wait a few years until we actually get cards that can fully use the pcie 3.0 slot.
 

Tig2575

Distinguished
Jan 31, 2012
28
0
18,540


I do understand the practical side of PCIe 3.0; I was just trying to ask more about the workings under the hood. What is the purpose of the controller chips, and why, if they're built onto the board, are they dependent on the CPU?
 

Tig2575

Distinguished
Jan 31, 2012
28
0
18,540



Not sure what you mean - "Just pick up a z68 board with pcie 3.0 and wait a few years until we actually get cards that can fully use the pcie 3.0 slot. " is a practical issue. I'm trying to understand the functionality of the PCIe 3.0 bus and its compatibility requirements, not asking for advice on a product purchase.