ScienceMark 2.0, Pifast
Regarding benchmarks that exhibit memory-intensive behaviour, which is a large portion of HEXUS' testing suite, ScienceMark 2.0 usually provides us with reasonable analysis on bandwidth and latency. The Model 3400+ adheres to the ClawHammer approach of using a single 64-bit memory controller that runs at full core speed. A DRAM controller, compliant at up to DDR400 speeds, interfaces with the on-board memory to provide the necessary data when requested. You'll notice that DDR400, which is 200MHz in common parlance, is 11x slower than the onboard controller's speed. That's the multiplier factor, as far as memory is concerned.
That's precisely why the Model 3400+ doesn't appear to do too well in this test. Adding a second 64-bit memory controller adds in considerable expense and pin complexity. The FX-51 is a prime example of both. It's of little coincidence that both the ClawHammer and the Barton XP3200+ (due to a double-pumped FSB) are tied in this benchmark. Note at how efficient a single-channel design seems to be. By rights, the Canterwood setup should be hitting 6GB/s.
Memory latency is exactly where the on-die design will excel in. Removing the controller's functions from the Northbridge reduces latency, and quite a bit of latency. ScienceMark 2.0 reckons that's the A64's is around 40ns better than the Canterwood's. Intel make noises at how much performance PAT adds to its DC chipset. PAT shaves off a few ns here and there. AMD's on-die controller takes a whole chunk off. That's one of the prime reasons why the Athlon 64 is, arguably, a better CPU than the Barton.
Consider the stone-cold fact that both the Model 3400+ and Barton XP3200+ run at 2.2GHz. The 3400+ takes nearly 6 seconds from the Barton's time. That's the benefit of clever, efficient design in a memory-dependant situation. And also consider that the 3400+ is running at a full 1GHz slower than the 3.2GHz Pentium 4. AMD's True Performance Initiative seems to be more than just marketing hyperbole now. We'd expect a time in the late 55s for a well-tuned S754 board.
