Many of you may have read our article that discussed the architecture behind NVIDIA's new GeForce 7800 GTX video card, but there are undoubtedly people who will not have read that. If you want to learn about some of the improvements that NVIDIA have made to the already good NV40 architecture, you can check out 'Inside the GeForce 7800 GTX' here. Some may have been confused by everything that we discussed in the first article, so we'll briefly summarise that article by giving you a run down of the specifications.
GeForce 7800 GTX is the first video card in the GeForce 7 series, and it is based on a 0.11-micron TSMC manufacturing process. This is the same process that was used for GeForce 6600 series, and GeForce 6200 series initially. It was then followed by NV41, which is the chip behind GeForce 6800 Std and GeForce 6800 LE. Finally, NV42, the chip behind GeForce Go 6800 Ultra, was released towards the back end of last year. Note that the chips are getting more and more complex as time goes by on this process – it allows NVIDIA to get the process right before creating their next-generation high end part on that manufacturing process.
It has 24 internal pixel pipelines, 8 vertex shaders and a 256-bit memory interface. In much the same way as the GeForce 6600 series, the pixel output engines (ROPs) are completely orthogonal, and despite there being 24 pixel pipelines, there are only 16 pixel output engines. We feel that this is a smart move by NVIDIA, and it allows the 16 ROPs in G70 to have a higher efficiency than those in NV40 and NV45.
The core is clocked at a conservative 430MHz, while the memory is clocked at an equally conservative 1200MHz. At a first glance, you may feel that there isn't enough memory bandwidth there for all 24 pipelines. However, NVIDIA have improved the efficiency of each pipeline dramatically, meaning that more work is being done on each pixel in every clock cycle. In some situations, the GeForce 7800 GTX will be up to and over two times the speed of GeForce 6800 Ultra.
The GPU is a native PCI-Express graphics processor, and thus has support for SLI – the heatsink at the end of the card is cooling the voltage regulators, and not a HSI bridge chip. SLI support is improving over time, and this driver release sees the addition of another twenty profiles that are predefined by the driver. You can, of course, add your own SLI profiles in order to make games work that don't have an optimised SLI profile created for them just yet.
The back plate has dual DVI ports and a TV-Out connector – it's still not possible to connect multiple monitors in SLI mode, but with SLI disabled there is support for up to four monitors if you have a pair of GeForce 7800 GTX's. There is a single power connector at the other end of the card – most of the power comes from the PCI-Express x16 interconnect, but there is additional power required for the GPU to operate at its full clock speed.