The relationship between CPU Multiplier & Memory Speed on AM2 processor
Bluetooth 26 May 2006

Background

If you are those people who love to fiddle with the multipliers and maximise the bandwidth of your DDR2 modules. There is something that we would like to share with you regarding the CPU multiplier and actual memory speed of your RAM modules.

In the K8 DDR world, we always run the memory in sync. That is 1:1, so your CPU at 300MHz, your RAM is actually at 300MHz (or DDR600). Some of the ram modules might not be able to take such high speed, you will lower it to CAS 3, 2T etc to make it run in sync.

In the DDR2 world, you can run the RAM in ASync mode to your CPU CLK. For example, our 4000+ runs at 10x200 (2GHz). In our tests, we ran the ram modules at CAS 5, 5-5-10, 1T cmd at DDR2-800 setting. Of course, we can also run it at DDR2-533 at CAS 3. We noticed that the actual difference in scores like 3Dmark won't differ by a lot. In fact, running at CAS 5, DDR2-800 gives some slight advantage.

Since we can run DDR2-800 and can score a good memory bandwidth score of 7300, it would be nice if we can push even further.

How abt DDR2-1066 ? We ran 1 pair of Corsair DDR2-1066 modules model TWIN2X2048-8500C5. Below is the Sisoft Sandra 2007 memory benchmark running the AM2 4000+ memory at DDR2-1066, CPU clk is running at 266 (x10) for 2.66GHz. So we are running CPU and memory in SYNC.

Now the important thing, did you notice from CPU-Z that it is 532MHz, that translates to DDR2-1066. The bandwidth we get is 10205MB/s.

Our next target was to test for DDR2-1200. As the CPU seems to be stressed out at 10x300. We have to resort to 9x300MHz. Something happened... read next page to find out.

Discuss in Forum

Next >>>

(C) Copyright 1998-2009 OCWorkbench.com