AnandTech: Intel P35 Memory Performance: A Closer Look

In our recent DDR3 vs. DDR2 review we discovered a 16% to 18% improvement in memory bandwidth with the P35 chipset. This translated into a 2% to 5% increase in real world performance in some computer applications. This represents a significant improvement in performance. Our review attributed the increase to the P35 memory controller, as we found no real difference in the performance of DDR3 and DDR2 on the new P35 chipset. Both memory types were much faster on P35.

While it is true that P35 exhibits these levels of performance improvement, the reasons for this performance boost are more complicated than the memory controller alone. If you look back at the test configuration, the P965 tests were run at 2.66GHz with an X6800 driving the tests at 10 x 266, while tests on the P35 used the same 2.66Ghz, but with an E6420 running at 8 x 333 speed.

The reason for these configurations was the problems with ratios on P965 and P35 motherboards. We wanted a test bench that examined the same speeds on all three tested boards. However, there is no way to run the P965 at a 333 base FSB (1333) with memory at either DDR2-800 or DDR2-1066. The available ratios do not allow this setup. Similarly the P35 chipset motherboards will not allow the DDR3-1333 setting unless the CPU is set to the 1333 speed. Setting the P35 to 10x266 limits the top memory base setting to 1066 without overclocking. With limitations on both sides the choice was made to test all boards at 2.66GHz, with P965 at 10x266 and P35 at 8x333.

This is a fair setup for the tested chipsets, since P965/975x were designed for 1066 FSB chips and official DDR2-800 memory and P35 is designed for 1333 FSB processors and official DDR3-1066 or official DDR3-1333 memory. P35 also is backwards compatible with 1066 FSB processors and it can also support DDR2 memory if the board manufacturer chooses. The 16% to 18% bandwidth improvement between these tested and representative configurations remains accurate and translates to a 2% to 5% real world improvement in several real-world tests.

In the review we attributed the performance increase to the P35, rather than the DDR3 memory. Technically this is correct, but there are two components at play in the performance increase. First the P35 memory controller itself is improved to provide better memory performance at the same memory speed and timings, and second the chipset supports the 1333 FSB which also improves memory performance. Since many readers have asked which is the primary factor in the memory performance increases - architecture or bus speed increase - benchmarks were set up to try to separate the impact of the memory controller improvement and the bus speed increase on P35.