i found this on the web..
One big issue in OCing is predicting the memory speed. The formula for memory speed is M-Speed = CPU-Speed / Divisor where the Divisor is CPU-Speed / 400 rounded up to the next higher integer. So, say using my rig: M2N32SLI, 4400 w/ Zalman 9500, 2GB Corsair 6400 C4 EPP, 2 x 74GB Raptor plus 2 x 250GB Samsung SATA Spinpoint, Samsung SH/S162 and Plextor 716 slot load, running at stock CPU-Multi = 11, CPU-Speed = 2200, Memory Clock Frequency (in BIOS) = DDR2800, Memory Speed = 2200/400 = 5.5 rounds up to 6. 2200/6 = 367 (733 DDR2). This displays the odd multiplier quirk. OK, all is understood.
But now, lets use the Memory Clock Frequency set to DDR2 667. The formula is actually Memory Divider = CPU-Speed / (BIOS Divider x 400), rounded up to the next integer. So BIOS Divider = Memory Clock Reference / Memory Speed and when using DDR2 800 for both equals 1/1 = 1 so makes no difference. But with Memory Clock Reference = DDR2 667 the BIOS Divider = 667/800 = 5/6 so now M-Speed = 2200 / (5/6 x 400) = 6.6 rounds up to 7. So Memory Speed = 2200 / 7 = 314 (628 DDR2).
Okay, Okay, I get that. But what happens when the memory being used is not DDR2 800, but say DDR2 667? What do you use for the denominator in the Memory Divider? Do you use 667 or do you use 800. Logic says you would use 667, but I don't know.
If that were the case, then if you still had the Memory Clock Reference set to DDR2 667, the BIOS Divider would be 667/667 = 1. OK. And if you reset it to 533, it would be 533/667 = 4/5. And with the setting at 400, it would be 400/667 = 3/4. But what about if you set it to DDR2 800, then it would be 800/667 = 4/3! Is this the case?
Qn1. What happens when you use DDR2 1000 or 1067 memory? Since DDR2 800 is the highest setting, you would end up with 800/1000 which means your higher speed memory is automatically divided.
Qn2. Or does the denominator always stay at 800, and if so, why? If this is the case, Why not just make the dividers what they are? 5/6, 2/3 and 1/2? Why create all the confusion?
i hope the experts out there can help verify whether the statements in bold are correct and help answer Qn1 and Qn2..
with regards to asus am2 mobos, are there only 4 settings for mem dividers (400, 533, 667, 800)?
Thanks a million!
One big issue in OCing is predicting the memory speed. The formula for memory speed is M-Speed = CPU-Speed / Divisor where the Divisor is CPU-Speed / 400 rounded up to the next higher integer. So, say using my rig: M2N32SLI, 4400 w/ Zalman 9500, 2GB Corsair 6400 C4 EPP, 2 x 74GB Raptor plus 2 x 250GB Samsung SATA Spinpoint, Samsung SH/S162 and Plextor 716 slot load, running at stock CPU-Multi = 11, CPU-Speed = 2200, Memory Clock Frequency (in BIOS) = DDR2800, Memory Speed = 2200/400 = 5.5 rounds up to 6. 2200/6 = 367 (733 DDR2). This displays the odd multiplier quirk. OK, all is understood.
But now, lets use the Memory Clock Frequency set to DDR2 667. The formula is actually Memory Divider = CPU-Speed / (BIOS Divider x 400), rounded up to the next integer. So BIOS Divider = Memory Clock Reference / Memory Speed and when using DDR2 800 for both equals 1/1 = 1 so makes no difference. But with Memory Clock Reference = DDR2 667 the BIOS Divider = 667/800 = 5/6 so now M-Speed = 2200 / (5/6 x 400) = 6.6 rounds up to 7. So Memory Speed = 2200 / 7 = 314 (628 DDR2).
Okay, Okay, I get that. But what happens when the memory being used is not DDR2 800, but say DDR2 667? What do you use for the denominator in the Memory Divider? Do you use 667 or do you use 800. Logic says you would use 667, but I don't know.
If that were the case, then if you still had the Memory Clock Reference set to DDR2 667, the BIOS Divider would be 667/667 = 1. OK. And if you reset it to 533, it would be 533/667 = 4/5. And with the setting at 400, it would be 400/667 = 3/4. But what about if you set it to DDR2 800, then it would be 800/667 = 4/3! Is this the case?
Qn1. What happens when you use DDR2 1000 or 1067 memory? Since DDR2 800 is the highest setting, you would end up with 800/1000 which means your higher speed memory is automatically divided.
Qn2. Or does the denominator always stay at 800, and if so, why? If this is the case, Why not just make the dividers what they are? 5/6, 2/3 and 1/2? Why create all the confusion?
i hope the experts out there can help verify whether the statements in bold are correct and help answer Qn1 and Qn2..
with regards to asus am2 mobos, are there only 4 settings for mem dividers (400, 533, 667, 800)?
Thanks a million!
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