IntroductionPCI Express. Who cares?
I'm sure the well heeled, keen enthusiast does, especially if he or she is an AMD Athlon 64 fan and is looking to nForce4 and VIA's K8T890 core logic-based mainboards for their next hardware fix. However, I'm quite certain that the non-habitual upgrader and gaming addict isn't upgrading their CPU and entire platform, just to get their hands on PCI Express graphics boards. Rather I'd imagine that the vast majority of you are waiting for the new PCI Express mid-range performance champions to show up on AGP. Those boards that dethrone the 9800 Pro and 9800 XT, that don't quite catch up with Radeon X800 and GeForce 6800 in terms of performance, but that don't catch up with those boards in terms of price either.
So you're looking to PCI Express, spying the Radeon X700 and GeForce 6600 releases we've seen recently, and wishing that platform's new mid-range boards would come to AGP. Well your wish is now granted. Sort of.
Building bridgesYou see, the rush to create native PCI Express SKUs has left the two major graphics IHVs with no choice but to bridge those SKUs back to AGP using extra silicon and new board layouts. That approach is cheaper and less problematic, at least for the IHV, if not the consumer, than creating identical SKUs with AGP interfaces. So if they want to sell their new products on AGP, they need PEG-to-AGP interface bridges. And those bridges need to work.
For NVIDIA, that's not been a problem. Their bridge chip has been working, inverted essentially, since PCI Express was launched, the company supplying a range of GeForce FX 5900 and 5700 AGP products on PCI Express using the bridge. They've also employed it with GeForce 6800 on PCI Express, NV45 employing the bridge silicon on the GPU's package, rather than off-package and somewhere else on the board PCB, as with the 5900 hardware.
So in its simplest terms, turning the bridge around lets them bridge PCI Express to AGP. And with the latest GPUs, that's correct. NVIDIA's GeForce 6600 GT today makes its appearance on AGP for the first time, some 5 weeks after the PCI Express version, using the bridge off-package. You'll see that soon.
But what of ATI and X700? Are they bringing that product to AGP soon? The simple answer is no. ATI's RIALTO PEG-to-AGP bridge appears unworking and at least unreleased at the time of writing. Instead, ATI continue to order R360 from their foundry partners, producing Radeon 9800 products in ever increasing numbers until such time as RIALTO can become a reality.
So NVIDIA's 6600 GT is the first PCI Express native SKU, as it is, based on NVIDIA's NV43 GPU, to be bridged back to AGP and put into mass production.
The big questions are therefore very simple. Is it as fast as the PCI Express version, does it outclass ATI's competing competing AGP products, how much will it cost and when will you be able to get your hands on it at retail. I'll try and answer those in turn.
Firstly, a refresher on just what NV43 is.