What speed ram for 4GHz i5 overclock

[shrex]

I just bought a i5 650 and a ASRock P55DE3. What speed ram should i get to be able to achieve at least 4Ghz.

 

[andy5174]

It depends on the BCLK set and the memory multiplier of IMC.

For example, if i5-650's IMC has choices of 6x, 8x and 10x and your BCLK is 200 then:

You would like to get,

8x200 = 1600MHz RAM
10x200 = 2000MHz RAM

p.s. Normally, you will find that 1600MHz RAM come with lower latency than 2000MHz and cheaper.

 

[shrex]

so 1333mhz is no good

 

[andy5174]

You could use 166/167MHz BCLK:

CPU
166x24 = 3984MHz
167x24 = 4008MHz

RAM
166x8 = 1328MHz
167x8 = 1336MHz

 

[shrex]

thanks, i went with a 2gb 1333mhz. I have set it to 166 bclk, seems to be the max i can get out of the cpu, tried adjusting the ram divider so i know2 its the Cpu that has topped out a 1.3725 volts, dont really ant to go higher.

My old core 2 e8400 went to 4GHz at 1.3625 volts so its a bit dissapointing that this i5 wont go any higher since it is 32nm.

 

[andy5174]

1) Are you aware that the BCLK is dependent on the QPI/Vtt voltage instead of Vcore?

2) Did you turn off the Turbo mode and HT? IMO, it would be worthwhile turning off HT if you can get at least 400MHz more without it.

 

[shrex]

I didnt know that, I tried upping the Vtt to 1.4v and the CPU PLL to 1.92v, but the max i could get is 4.15GHz, even tried upping the cpu voltage.

Turbo mode is off and switching off hyperthreading didnt improve my overclock

 

[wolfram23]

I have my i5 750 on an MSI P55GD65 mobo with a bclk of 200, the vcore is at 1.178V, PLL is at stock, and VTT I raised up the most, although I forget the value right now I think it was 1.6 or 1.7V (basically I think it was a 0.2V increase). I'm running at 3.6ghz (200x18). I haven't tried 4ghz yet since I don't have a reason to do it but from what I've read the VTT would have to be up around 1.8 or 1.9, PLL doesn't have to go up much (unless I misunderstand, but it's related more to QPI than CPU speed - so related to FSB) and then vcore might be around 1.2V.

Also, I wasn't aware the i5 650 could use hyperthreading, I thought that was only in i7s.

Anyway I hope I've helped a little.

 

[shrex]

My bclk is only at 173, havent been able to go higher, core i5 650 has a 24x multi but cpu-z shows 25x, so i dont really know what my clockspeed really is currently its showing a core speed of 4325MHz, multiplier 25x, QPI link is 4152MHz.


All Core i5 CPUs have Hyperthreading apart from the i5 750

 

[EXT64]

Sure Turbo is Off?

Also, do you have the newest CPU-Z?

 

[shrex]

yes turbo is off, if turbo is on it sometimes changes to 26x multiplier. I have set the multiplier to 24x but cpuz still show 25x. I put the blck back down to 166, 173 wasnt stable.

this is the latest version of cpu-z