2 - The G92 Graphics Core Explained
Alright, before we start off a little 101 on the silicon that is empowering this graphics card.
The GeForce 9800 GTX is based on the same microprocessor as the GeForce 9800 GX2 and for that matter the same as GeForce 8800 GTS 512MB. They're all products developed with a chip called G92 (codename).
The G92 silicon is based on NVIDIA's newer 0.65nm silicon. it is a respin chip based on last years architecture from the GeForce 8800 series. See while this GPU architecture is 95% the same as the good old G80 (GTS/GTX/Ultra) core there are some very distinct differences
The first being the fabrication process. It was moved from 90nm towards 65nm, meaning a smaller die-size, likely resulting in lower core voltages, better energy efficiency and perhaps better clock speeds. Important to know is that the G92 is based on the same chip as the 8800 GTS 512MB has, which means that the GPU on the 9800 GTX also has 128 shader processors.
How many transistors do the NVIDIA GeForce 9800 GTX GPUs have you ask ? 754 million transistors.
Interesting, if you take a peek at the clock speeds you'd might even think that one G92 GPU could beat a GTX. Well shader processors are not the only part of the equation, because at the end of the pipeline there are these things called ROPs, and that's where the old GTS (20 ROPs), and this G92 (16 ROPs) become a little castrated compared to the GTX (24 ROPs).
Next to that, the G92 is utilizing memory differently compared to the older 8800 GTX. The 8800 GTX is addressing the memory bus faster (384-bit) as opposed to the G92 with 256-bit, and that's less memory bandwidth to play around with.
In reality the performance differential between the two cards is small though, as our benchmarks will show. Though higher resolutions with high AA levels would give the older 8800 GTX with more memory and a faster memory bus the advantage.
A question that I hear a lot, why is the 9800 GTX 512MB a series 9 product, and the 8800 GTS 512MB based on the same G92 graphics core, a series 8 product? My answer: I have no idea other then the fact that a Series 9 product sounds better (marketing wise). The G92 based 8800 GTS should probably have been called 9800 GTS or GS as people in the stores right now are really confused.
So in summary, the new features of G92 opposed to the G80: Smaller 65nm fabrication process, silicon optimizations (compression algorithms), usage of 256-bit memory, and compared to the older GTS models a higher shader processor count at 128 sub-cores. The core frequency runs at 675 MHz, the shader processors at 1675 MHz and the memory at 2200 MHz effectively (70.4 Gbps memory bandwith); mind you that these are reference speeds.
Also the new Series 9 cards are Hybrid Power ready, meaning on future Hybrid mainboards this card can deactivate itself (saving power). One more advantage for the 9800 GTX is that you can go three-way SLI with it. And that might be a sweet-spot if the prices come down a little. More on that later though.
