Haddock: you really think that the more agressive memory controller of the Athlon 64 can compensate for only having one memory channel. I find that hard to believe.
Registered DIMMs have a higher latency than non-registered DIMMs.
Additionally, there is a latency decrease of 20% resulting from the higher clock frequency (Opteron uses DDR333, whereas A64 will use DDR400).
The higher clock frequency also yields an increase in peak bandwidth, so the comparison is: 128bit x 333 versus 64bit x 400. I.e. Opteron only has a 66% higher maximum theoretical bandwidth, not 100% higher.
Combine this with a more aggressive memory controller and, yes, I believe A64 will be very competitive with Opteron in most non-synthetic (but still memory intensive) applications and benchmarks.
-fyo
Market Data 
Markets 
AI
