Anatomy of NVIDIA's NV45
While ATI's X600 XT, a PCI Express 16x board built around ATI's RV380 GPU, was used for the main subsystem benchmarks in this article, it was NVIDIA's NV45 that powered the PCI Express boards used for the 3D comparison coming up. Simply a matter of logistics, with the handy fact that NV45 and the 6800-series boards it powers are CPU limited in a number of tests, the NV45 provided the perfect foil for the NV40, the NV45's AGP counterpart.With both 6800 Ultra and 6800 GT to hand on both PCI Express and AGP, a simple 3D performance comparison between an AGP-equipped FX-53 system and the Alderwood system running the 3.4GHz Extreme Edition was easy to do.
First of all though, a quick look at an NV45 with its clothes off.
NV45 is nothing more than NV40 with an off-die AGP-to-PCI Express bridge chip, translating the AGP interface on the NV40 to an external electrical PCI Express interface on the other side of the bridge. There's a little more to it than that, NVIDIA's High Speed Interconnect (HSI) bridge offering up higher than AGP8X performance when bridged to PCI Express, but the inner workings of the HSI will have to wait for a separate article.
Before we see the NV45-based 6800 Ultra nude, a simple comparison shot of the NV45 in bed with an identical NV40.
Removing its heatsink and fan assembly is simple. Undo the screws on the back holding the fan shroud and the memory heatsink on, before removing them to get access to the GPU heatsink. Whereas the NV40 Ultra reference sample, and all retail Ultra boards up to just that use that cooler, has an aluminium GPU heatsink, it was a surprise to see the NV45 Ultra come clad in copper.
Removal of the main heatsink is a matter of undoing four screws, letting you see the NV45 die and the HSI bridge close by.
You can just about make out the NV45 die inscription, through the liberal application of thermal compound. Similar nude photographs are to be had if you strip the 6800 GT PCI Express board bare.