Core details - Pipelines, manufacturing, etc.

As we stated on the second page, GeForce 7800 GTX is built on a 0.11-micron manufacturing process at TSMC. This is the same process NVIDIA used for GeForce 6600 GT, and ATI uses today for their RADEON X700/X800/X800 XL cards.

As we’ve outlined in previous articles, TSMC’s 0.11-micron process is built for value, not high clock speeds (as 0.13-micron was). This means that performance-enhancing features that are found at 0.13-micron, such as low-k dielectric aren’t present at 0.11. In case you don’t know, low-k dielectric is a material used to insulate the copper circuits within the graphics core. This is important, because TSMC’s 0.13-micron process packs the circuits within the chip more tightly together. As clock speeds increase, these circuits can begin to interfere with one another in the same way crosstalk can occur on telephone lines. This form of electrical crosstalk can hamper performance and waste power.

7800 GTX die shot

And here is a 7800 GTX wafer

Low-k dielectric material is used to encapsulate the copper wires from each other, ensuring better performance (and thus, higher clock speeds) and lower power requirements. TSMC reserves low-k for their 0.09-micron and 0.13-micron processes, charging their customers such as NVIDIA more for this feature.

0.11-micron is essentially TSMC’s die shrink of 0.13-micron without low-k, and therefore without the price premium. For GeForce 6600 and RADEON X700, this allowed ATI and NVIDIA to incorporate more pipelines into these value parts affordably.

For GeForce 7800 GTX, NVIDIA is essentially doing the same, using the smaller process to more affordably incorporate more features into GeForce 7800 GTX. In this case, that means more pixel and vertex pipelines; with the chip encompassing a whopping 302 million transistors! In comparison, GeForce 6800 Ultra featured over 220 million, while an Athlon 64 FX CPU contains roughly 106 million.

500MHz or bust?

The only real downside to 0.11-micron is, as we mentioned, lower clock speeds. ATI ran into problems getting X700 XT to yield well with sufficient quantities, while the X800 XL is clocked at 400MHz with 16 pipelines.

Starship Troopers

Serious Sam 2

Another Serious Sam 2 shot

NVIDIA clocks the GeForce 7800 GTX at 430MHz on the graphics core, this is an improvement of only 30MHz over the stock GeForce 6800 Ultra (we mention the word “stock” because many of NVIDIA’s 6800 Ultra board partners chose to clock the core of their boards at 425MHz). The memory subsystem runs at 600MHz (1.2GHz effective), this is 50MHz higher than the GeForce 6800 Ultra providing up to 38.4GB/sec of peak memory bandwidth (versus 35.2GB/sec in GeForce 6800 Ultra).

At first, these figures may not seem that significant for a “next-generation” product, but when you factor in the efficiency improvements NVIDIA has incorporated into the shading and texture units, the card should come closer to hitting its theoretical specs. That’s the theory at least…