By developing a partnership with IBM, Nintendo was able to get their hands on Gekko - .18-micron, copper interconnects, all running at 405MHz. Derived from IBM's PowerPC architecture, Gekko features 256KB of L2 cache that is 2-way set associative. The L1 is split between 32KB of instruction cache and 32KB of data cache, both 8-way set associative. With its 64-bit external bus running at half the processor frequency (or 202.5MHz for those who don't feel like dividing 405MHz by two) Gekko is able to push 1.6GB/s of bandwidth. It is important to remember that this number applies only to data transfers from Gekko to the video processor (Flipper) and back, so worries about graphics bottlenecks are not yet warranted.
If you are a veteran of PC gaming, you have likely heard that a PC's host CPU is responsible for processing artificial intelligence, physics and database traversal while the graphics accelerator handles the brute rendering. The GameCube is very similar, so you may think of it as a PC hybrid. Because the primary function of the GameCube is, of course gaming, most of the action doesn't take place on the host processor, but on the video accelerator.
Graphics giant ATI has seen significant success with their RADEON GPU, as well as the M-series of mobile accelerators (not as much success as BMW has had with their M-series, though). With their recent acquisition of ArtX, ATI also gained the opportunity to make a contribution to Nintendo's GameCube.
Code-named Flipper, ATI's chip serves as a north and south bridge with integrated graphics. The processor is composed of 51 million transistors and measures a scant 110 square millimeters - more transistors than the Pentium 4 and half the size. To combat bandwidth issues, Flipper includes 1MB of embedded texture cache, 1MB of RGB frame buffer and a 1MB Z-buffer cache that is estimated to deliver a total of 22GB/s of bandwidth.
If the data needed by the processor is not resident in the embedded cache, Flipper has access to another 24MB of 1T-SRAM with a sustainable latency estimated at around 10ns or lower. This external memory bank provides up to 3.2GB/s of bandwidth. Those who have read our Pentium 4 Review or the specifications of Sony's Playstation2 know that dual RDRAM channels provide the same theoretical bandwidth. The difference is Nintendo's 1T-SRAM isn't subject to the same latency penalties suffered by Rambus' technology, making data access quicker on the GameCube. Additionally, block transfers are much smaller, making them more efficient.
While ATI wouldn't give us any details regarding the polygon output of the GameCube, we have heard that the number will end up between 6 and 12 million achievable textured polygons. We say achievable because the outrageous numbers listed by Sony for the Playstation 2 are peak, and may never be reached after texturing and lighting have been applied to the application. The hardware capabilities of the GameCube are also pretty impressive - features include hardware lighting (eight sources), sub-pixel anti-aliasing, bump/environment mapping, real-time texture compression and even hardware motion compensation.
Flipper will also provide the GameCube's audio, and that part will be clocked at 101.25MHz. Although the 16-bit DSP is capable of processing 64 simultaneous voices, we aren't expecting any overwhelming audio features for the Gamecube's launch. According to ATI, the Cube will initially only support 2-channel audio, meaning those expensive home theater systems will be blaring a mere stereo signal. There will be 16MB of 100MHz DRAM onboard that may be accessed by the audio processor and other subsystems. This memory bank has been dubbed the A-Memory and has been described by ATI as "bridging memory."