Intel P35 Memory Performance: A Closer Look
by Wesley Fink on May 18, 2007 12:00 PM EST- Posted in
- CPUs
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.
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.
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TA152H - Friday, May 18, 2007 - link
I've looked over these numbers a few times, and tried to make some sense of it, and the remarks about the x6800 being slower on SuperPi, but faster on other things.There were a few clear patterns, which SuperPi managed to break, which leads me to a conclusion that this benchmark needs to be looked at closer.
For example, I noticed that DDR3 shows a greater advantage at the 1333 FSB setting, and starts leaving DDR2 behind. Except on SuperPi.
In every benchmark, 1333 FSB is faster. Except in SuperPi.
The x6800 is faster than other processors on benchmarks at the same settings, except on SuperPi.
Ummmm, anyone else think that there might be something amuck with SuperPi and it probably should be looked at more closely and possibly be removed as a benchmark until it is KNOWN to work correctly. It seems completely wrong. However, if it is reporting correctly, it would be very informative to know why it runs exactly opposite everything else. Is it using the processor in an unusual way? If so, what other applications do, so people know when to pay attention to it, and when not to.
I think the most interesting thing is how the DDR3 likes the 1333 FSB a lot more than DDR2 does. It's clearly the memory of the future.
noobzter - Friday, May 18, 2007 - link
Wes, could you elaborate on that? I've always wondered whether there's any difference between running C2Ds at higher multiplier and higher FSB (e.g. 13x267 vs 10x347)
Wesley Fink - Friday, May 18, 2007 - link
Several editors have noticed that the X6800 at the exact same speed and timing settings is a bit faster in gaming performance and a bit slower in Super Pi performance compared to other C2D processors. This is somewhat contradictory, but .We really don't know why this is the case, but we have seen it over a number of boards and in quite a few test configurations. While we don't know exactly what is different about the X6800 Extreme to make it perform this way, we do know the X6800 Extreme behaves a littel differently in benchmarks. We've asked Intel, but we have never received an answer that explained these minor differences to us.
IntelUser2000 - Friday, May 18, 2007 - link
I can explain that. When Core microarchitecture based CPUs first came out, Intel talked about being able to optimize the prefetchers for the target segment. Mobile chips would have less aggressive and power optimized prefetchers, Desktop chips would be performance optimized(relative to the mobile) and the Xeon variants would be fit for the server/workstation workloads. I would assume the "X" chips could be optimized for gaming, and that may explain the difference.
How much faster is it btw??
Wesley Fink - Saturday, May 19, 2007 - link
If you compare the 1333 gaming numbers from the ddr3 vs. ddr2 review to those in this review you will see the exact difference at the various settings. The ddr3 vs. ddr2 were run with an E6420 at 8x333, while this review used the X6800 at 8x333.Deusfaux - Friday, May 18, 2007 - link
I would guess it would have to do something with cherry picking those particular cores in the fab process and thus getting you the procs from the top of the heap that are just a wee bit better at everything and why they can also justify selling it for such a markup.yacoub - Friday, May 18, 2007 - link
I'd love to know how much performance can be gained on 650i-SLI board going from 10x266 to 8x333. I currently run 10x266 E4400 @ 2.67GHz. I wonder if I'd gain any performance running it at 8x333 and if it'd be worth the added stress to the motherboard to run at 1333MHz fsb. It's an MSi P6N-SLI Platinum.yacoub - Friday, May 18, 2007 - link
Also do I leave my PC6400 DDR2 RAM at 800MHz default or raise it a bit (they don't do 1066 very well), but I could lower them to 667MHz if for some reason it was more ideal to run a 1:2 multiplier from the 333MHz fsb than leaving them up at 800MHz.vailr - Friday, May 18, 2007 - link
Why don't you use the latest beta version Intel chipset drivers?[Instead of: System Platform Drivers Intel - 8.3.0.1013]
Version 8.4.0.1010 Beta:
http://www.station-drivers.com/telechargement/inte...">http://www.station-drivers.com/telechargement/inte...
Wesley Fink - Friday, May 18, 2007 - link
Intel tells us there are no performance imnprovements in the beta drivers. The beta drivers fix a few compatibility issues with Vista. We prefer to use release drivers unless there is a compelling performance or new release reason to use beta drivers. Gary is not testing with the new beta drivers either.