Integrated Memory Interface: No Northbridge Meddling
The concept of the Opteron multi-processor systems includes local memory on each CPU, but other CPUs can access the memory of these CPUs via the XBAR switch and the HyperTransport bus. Initially, only the server version of the Hammer, the Opteron, will be equipped with two 72 bit wide DDR SDRAM channels. With a total of eight DIMM slots, this allows each processor to address 8 GB. Opteron's dual-channel interface offers a memory bandwidth of 5.4 GB/s per processor. With each CPU having its own memory, the memory bandwidth scales linearly with the number of CPUs.
Still, the integration of the memory controller can also be considered as limit of Opteron's flexibility. Starting from 2004, the DDR2 memory standard will be established in the market, and AMD will have to make modifications to the CPU. Ironically, as a result, Taiwanese chipset manufacturers have their own solution ready, which disables the CPU's internal memory controller and features a conventional memory controller integrated in the Northbridge. This would take us back to where we started.
Fab30 Yield: Max. 89 Opteron CPUs Per Wafer!
AMD only uses wafers with a diameter of 200 mm (Intel uses 300 mm wafers today), which results in a total silicon surface of 31416 mm². The quotient of wafer surface and the size of the CPU die gives you the theoretical yield without geometric waste. With the 200 mm diameter wafers, it's been shown in the production process that the average waste is 9%. This gives you a theoretical yield of 148 CPUs, as long as the yield rate is 100%.
In practice, it's been shown that up to almost 60% yield can be attained during the production process. The result is 89 CPUs per wafer. Information about exact numbers is strictly confidential, but our calculations are certain to come pretty close. In the first months of production however, we doubt that the yield will be any more than 30% - this is based on information from other chip manufacturers that use similar processes.
A wafer with Opteron CPUs: if everything runs optimally, than AMD can get approximately 89 Opterons from one disc. This is based on internal THG calculations as well as information from other sources.