PCB Design and Specifications
The GeForce 8800 GT will be mostly manufactured for Nvidia at contracted facilities and delivered to the company’s partners in ready-made form. So, besides the standard versions of the card, you can only see pre-overclocked versions and/or versions with a unique cooling system, but most often it will be a standard version with a different sticker on the cooler. We don’t dismiss the possibility of such graphics cards coming out with an original PCB design, though. Major graphics card makers are quite capable of developing an eight-layer PCB with a 256-bit memory bus.
The new GPU from Nvidia has a 256-bit external memory interface and doesn’t require an additional NVIO chip, so its PCB design is simpler than that of the GeForce 8800 GTS, with 8 layers instead of 12.
Both PCBs have the same length of 22.8 centimeters but the components are placed quite differently on the GeForce 8800 GT just because the memory chips are installed in a semicircle around the GPU like on Nvidia’s GeForce 7 series cards. Being optimal for a 256-bit memory bus, this solution is employed by both Nvidia and ATI Technologies.
The power section resides at the back of the PCB, as usual. It is about as complex as on the GeForce 8800 GTS, but some elements are not installed, which indicates a low power draw of the GPU even when it is pre-overclocked by the manufacturer. This PCB may also be used for more advanced G92-based graphics cards where the eighth unit of texture and shader processors is unlocked. The power circuit is governed by a four-phase digital PWM controller Primarion PX3544, which is alike to the PX3540 chip employed on GeForce 8800 GTX/GTS. Four out of the controller’s three phases are used here: the elements of the fourth phase are not installed on the card. A simple PWM controller Intersil ISL6549CBZ is responsible for power supply of the memory chips. A piezoelectric speaker is located in the top right corner of the PCB – it informs the user with a warning signal about problems, for example when the additional power is not attached to the card. The card has a single power connector, a 6-pin rather than an 8-pin PCI Express 2.0 one, which is yet another indication of a relatively low level of power consumption of the GeForce 8800 GT.
The card carries eight GDDR3 chips (Qimonda HYB18H512321BF-10) in FBGA-136 packaging. These chips have a capacity of 512Mb (16Mbx32), a VDD and VDDQ voltage of 2.0V, and a rated frequency of 1000 (2000) MHz. The eight chips provide a total of 512 megabytes of graphics memory accessed across a 256-bit bus. Although the standard memory frequency of the GeForce 8800 GT is 900 (1800) MHz, it is pre-overclocked on this card to 1000 (2000) MHz, which provides the same memory bandwidth of 64GB/s as on the GeForce 8800 GTS.
As opposed to the G80, the G92 uses the traditional open type of packaging with a metallic protective frame but without a heat-spreading cap. There is a place left around the chip for a protective frame like on the GeForce 8800 GTX and GTX, though.
The die is relatively small. It is comparable to the G70 and much larger than the G71 although incorporates 2.5 and 2.7 times as many transistors as these previous-generation cores. Such a compact core is manufactured using the thinner 65nm tech process. The marking says that this is a third revision chip manufactured at the 40th week of 2007, which is early October. The main domain frequency is increased from the standard 600MHz to 680MHz and the shader domain is clocked at 1700MHz, which is 200MHz higher than the standard value and should ensure a good performance gain in games.
The left part of the PCB is interesting, too. You can see that the GeForce 8800 GT allows for the installation of a HDMI connector instead of the top DVI port. There is also an empty seat for a rather large chip here. We don’t know the purpose of it. Perhaps this is a place for the converter that supports the DisplayPort interface or Nvidia may be planning to endow the GeForce 8800 GT with the audio-over-HDMI feature to catch up with ATI’s products.
In the most widespread version the GeForce 8800 GT has two DVI-I connectors with support for dual-link mode and a universal 7-pin video output that supports Composite, S-Video and YPbPr output. The card can also be used in SLI configurations and has a MIO interface connector for that. Configurations with more than two cards, available with GeForce 8800 GTX and Ultra, are not supported because the card has only one such connector.