chr_p, fasinating find, that assymetric Opteron/A64 design! It does get over the problem we mentioned yesterday that you can not make a practical configuration with two A64s. In that case, the lone aHT connection from the A64 goes into one of the connections on the Opteron, and the Opteron handles all the I/O.
Technically feasible, but silly, IMHO. First, it would require the OS to support distributing threads based on the characteristics of the microprocessor. I'm not sure how many applications can be written this way. Next, applications tend to do most of their hard work in the background tasks (because the foreground task is interacting with the users). (Note: Some games are an exception to this rule.) For most things, the CPU-hungry background task is being delegated to the wrong CPU!
Your question: Why use regular DDR on the Opteron? Saves cost, improves performance over buffered DDR. I'm not sure you can actually populate a processor with 8GB of regular DDR right now, but this slide projects such a configuation. Usually you use buffered DRAM to get this size configuration.
I see this diagram as a bit of 'blue skying' - showing what is possible, not what is feasible.
I think I will send Peter an email - his address is on the first slide. Maybe he can shed some more light on it.
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