On Asus P5K-series there are two strap changes:
At 293FSB the board changes FSEL strap to 1333FSB to make more memory dividers available. This doesn´t have any effect to performance.
The performance level is also changed for following dividers:
1:2 Performance level changes from level 2 to level 1
Level 1 is the tightest possible, so expect some huge bandwidth
Dividers 3:5 & 1:2 are FSEL strapped to 800FSB.
At 500FSB the performance level of all dividers are set more loose.
1:1 Performance level changes from level 6 to level 10.Level 10 is the loosest one. Usually the chipset can handle level 5 just fine
5:6 Performance level changes from level 5 to level 8.
Setting level 4 should not be a problem.
4:5 Performance level changes from level 4 to level 7.
Setting level 4 - 3 should be fine.
Since the memory frequency would get a bit high at bigger dividers I don´t have actual values for them. But I recon the values would be following:
2:3 Level 3 -> Level 6
5:8 Level 4 -> Level 7
3:5 Level 2 -> Level 5
1:2 Level 1 -> Level 4