January 2004
I recently built a new computer and was interested in how fast I could make it go. Here's what's inside:
- Abit IS7 motherboard
- Intel 2.6GHz Pentium IV with hyperthreading
- 1G RAM of Crucial (Kingston) PC3200 (DDR400) (2x512) in dual mode
- ATI Radeon 9600XT
After some fiddling around I determined that I could run the FSB at 240MHz but the memory wouldn't run at this speed. (Even with the memory voltage jacked up to the maximum rating of 2.7v.) The Abit IS7 contains a setting in the soft menu for the ratio between the CPU and memory clocks. In the bios it is labeled DRAM Ratio (CPU:DRAM). See the pic below. I set this to 5:4 so the CPU clock runs at 240MHz but the memory runs at 192MHz. I thought this was a bust because the memory didn't run as fast as its supposed to (200MHz by default).
So I put the ratio back to 1:1 and started clocking up the FSB again. At the 1:1 ratio it will run at a front side bus speed of 225MHz. (Actually it may run a little faster, but if set at 230MHz it will eventually crash in Sandra's burn-in wizard.)
So I was curious which config was better. I figured the 225MHz FSB would be better due to the faster memory bus. Let's see...
Config 1 - FSB=240MHz
In this config the FSB has been increased to 240MHz but the CPU:DRAM clock ratio is set to 5:4 which sets the memory clock at 192MHz.
Config 2 - FSB=225MHz
In this config the CPU:DRAM clock ratio is set to 1:1 so the CPU runs slower but the memory runs faster.
Observations And Conclusion
Here are the numbers from the benchmarks shown above.
| CPU Clock | Memory Clock | CPU Arithmetic Benchmark |
Multimedia Benchmark |
Memory Bandwidth Benchmark |
Cache & Memory Benchmark |
|
| Config 1 | 3.1GHz | 192MHz | 9792/3921/6865 | 23935/34367 | 5199/5174 | 7648/3056 |
| Config 2 | 2.9GHz | 225MHz | 9155/3681/6461 | 22452/32160 | 5125/5122 | 7200/3600 |
I thought config 2 would be better since the memory clock was running at 225MHz vs. the 192MHz of config 1, but the Sandra benchmarks show otherwise. Config 1 is clearly the winner with the CPU clocked up and the memory clocked down. This is probably helped by the fact that the motherboard is able to run the memory with a CAS of 2.5 in config 1 vs. a CAS of 3 in config 2. The only area that config 1 lags config 2 is in the Cache & Memory Benchmark when moving large amounts of data (1Mb+, see config 1 line chart).