This helps avoid interference in the RAMDAC that could be caused by the shader processors working at 1.35GHz, and improves the chip yield of the new GPU. This solution makes the wiring of the new PCB somewhat more sophisticated, though. The external NVIO chip may also serve some other purposes besides just outputting the image. By the way, the NVIO is a kind of return to the roots because graphics cards once used to employ external RAMDACs.
History likes to tell the same old story anew: the last time we saw a GPU package with a metal heat-spreader, it was the Nvidia NV35 chip. The company abandoned it with the release of the NV40, limiting itself to a protective frame around the die. The high power consumption and the non-uniform heat dissipation of the different parts of the new GPU made Nvidia return to the heat-spreader idea. As a result, the G80 looks not unlike the modern CPUs from Intel and AMD. This design ensures better heat transfer and minimizes the risk of damage to the fragile die. The cooler of the GeForce 8800 being rather heavy, there is a metal frame around the GPU, fastened right to the PCB with 8 small screws, to avoid putting too heavy a weight on the chip as well as to distribute the weight of the cooler uniformly on the PCB.
The CPU marking doesn’t tell its codename or official name. There is only the updated Nvidia logotype there. The marking shows the date of manufacture and the chip revision. Here, it is the 37th week of the current year, i.e. between the 11th and 17th of September. At that moment Nvidia already had fully functional revision A2 samples of the G80, i.e. the third revision of the chip. The number 507 is written in the top left corner with a blue marker. Perhaps it is a unique number of the chip or graphics card.
The clock rate of the GeForce 8800 GTX GPU is 575MHz, which is an achievement for a 0.09-micron die consisting of 681 million transistors. This is not a limit, though. The shader processors in the senior GeForce 8800 are working at 1350MHz. The G80 architecture resembles Intel’s NetBurst in this respect: the ALUs work at two times the main frequency there.
The circular placement of memory chips when some of them are installed at an angle of 45 degrees has been changed for a simpler placement: the 12 GDDR3 chips are positioned around the GPU in three straight rows, two vertical and one horizontal. Each chip is organized as 16Mx32. They are accessed across a 384-bit bus. The junior GeForce 8800 GTS carries only 10 chips on board, which narrows its memory bus to 320 bits.
These Samsung’s K4J52324QE-BJ1A chips are a RoHS version of the widespread K4J52324QC series. The manufacturer’s website doesn’t yet describe them, but they seem to be the same 2.0V chips capable of working at frequencies up to 900 (1800) MHz. This is indeed the frequency the chips are clocked at on the GeForce 8800 GTX card. The use of a 384-bit memory bus helped Nvidia achieve an impressive memory bandwidth of 86.4GB/s without installing the rare and expensive GDDR4.
There are two MIO connectors in the top left corner of the PCB. This may mean different things: 1) bi-directional data transfers, 2) increased bandwidth by using both the MIO interfaces integrated into the GPU at the same time, 3) an opportunity to use four GeForce 8800 GTX cards in a Quad SLI configuration. Although it’s hard to imagine such a monster in a home PC – 8 power connectors and a power consumption of over 500 watts – the latter thing seems plausible. This is also confirmed by the fact that the junior GeForce 8800 GTS has only one MIO connector and Nvidia wouldn’t have reduced the efficiency of a SLI tandem you can build out of two such cards just for the sake of paltry economy. Quad SLI is quite a different thing. It is a premium technology that is targeted at a narrow group of users who want to have the highest performance possible whatever its price may be. Looking for more speed, such users will buy the GeForce 8800 GTX rather than the cheaper GeForce 8800 GTS, for which the option of working in a Quad SLI subsystem is virtually unnecessary.
The configuration of the external connectors is standard: two DVI-I ports with support for dual-link and HDCP, and a universal 7-pin S-Video/YPbPr port. The card lacks VIVO functionality, but that’s not at all important today.