Performance

First of all, we decided to take a closer look at the performance of the built-in memory controller. Especially since we haven’t yet had a chance to play with the DDR SDRAM controller built into a CPU, even though some similar technology is used by SoC solutions developers.

First let’s check the numbers obtained in Cachemem benchmark, which we always use when there is a new memory controller tested:

This table sums up the data obtained for three different memory controllers: the one integrated into Athlon 64, the one from the nForce2 chipset and the one from i875P chips. All controllers were used with DDR400 SDRAM, nForce2 and i875P worked in dual-channel mode.

As we see, the single-channel Athlon 64 controller is much faster than the dual-channel controller of the nForce2 core logic, which cannot show its best because of the limited processor bus bandwidth. At the same time, Athlon 64 had hard time trying to compete with the bandwidth of i875P dual-channel controller. But as soon as it comes to latency, Athlon 64 becomes an indisputable leader having left all the rivals far behind. Thanks to this processor’s ability to work with the memory directly, the latency during work with the system memory turns out very low.

Almost the same conclusions can be drawn from the results of the memory test from ScienceMark 2.0:

If we compare cache-memory performance of Athlon 64
with that of Athlon XP, the results can be really interesting.

The diagrams above show the results obtained in an Athlon 64 system (top) and Athlon XP system (bottom). Both CPUs work at the same clock frequency: 1.6GHz. Besides the higher bandwidth and lower latency, the screenshots show that Athlon 64 boasts faster cache-memory. Some time ago there circulated rumors about AMD’s intention to implement a broader bus between the Athlon 64 processor core and the L2 cache-memory. Maybe higher cache-memory performance is exactly the outcome of this modification.

One more tool, which we will use to check the memory subsystem performance is SiSoft Sandra 2003 benchmark:

The results of Athlon 64 2800+ with DDR400 SDRAM
are simply impressive!

We haven’t yet seen a memory controller as efficient as this one! The practical DDR400 SDRAM bandwidth measured in Sandra2003 test equals 96% of the theoretical one. The integrated memory controller is evidently a very efficient solution.