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Help me get my i5 750 to a stable 4Ghz

Discussion in 'Overclocking & Cooling' started by tywyn, 21 Mar 2010.

  1. tywyn


    Joined: 12 Jan 2009

    Posts: 122

    I've managed to get a stable 3.8Ghz on my i5 750/P7P55D Pro/G Skill Ripjaw combo but I'm unable to get a stable 4GhZ overclock. I ran Prime on the 3.8GHZ O/C for 5 hours yesterday and 3 hours today without any error. The memory is running at 1.65v @ 7-7-7-24.

    I have set Line Load Calibration in the BIOS to enabled (which is the same as VDroop) but Prime 95 is failing after a few mins on 200 BCLK x 20. I've had the Vcore as high as 1.4v and the IMC (equivalent to the VTT) up to 1.35, but still no joy. I'm using a Thermalright Mux 120 for cooling, but only an OCZ Xstream 600w PSU.

    Last edited: 21 Mar 2010
  2. OpenToSuggestions


    Joined: 5 Aug 2006

    Posts: 11,113

    Location: Derbyshire

    For a start I would say the PSU is fine. OCZ are a decent brand and 600W is as lot of power for a rig with 1 gpu.

    You sure the ram is rated to do 7-7-7-24? I got some G.Skill Ripjaw ram from OCUK yesterday and it is rated 8-8-8-24. Only the expensive stuff does 7-7-7-24.

    What temps do you get from Intel Burn Test? As this program creates temps like no other.
  3. tywyn


    Joined: 12 Jan 2009

    Posts: 122

    Thanks for the reply.

    Yes the RAM is rated at 7-7-7-24 @ 1.65v as I bought it back in September when it was £65, but only last week bothered to get a premium cooler and O/C due to BFBC2 :)

    I'll try the Intel Burn test again, as when i tried it on Friday I got a BSOD, but that was with different settings.

    Edit: Should I run the standard or max test in Intel Burn test?
    Last edited: 21 Mar 2010
  4. Chapa


    Joined: 26 Feb 2010

    Posts: 34

    Im having the same problem with my rig.

    i5 750
    Gigabyte P55 US3L
    OCZ platinum 1600mhz

    I have my rig stable at 3.8 ghz vcore 1.1875.

    But when i go up to 200 fsb x 20 for a 4.0 Ghz. using 1.25 vcore is not stable.

    What temps are safe?
    Using 1.25 vcore unstable my temps are 66 degrees at full load.

    Need some advice.

  5. OpenToSuggestions


    Joined: 5 Aug 2006

    Posts: 11,113

    Location: Derbyshire

    **** you I just paid £95 for some G.Skill Ripjaw 8-8-8-24 on sat:p
    Shows that pc pricing depends on our £ strength more than anything else!
    Intel Burn Test basically nails the cpu harder than any other test, even though in any real world usage the cpu would not get that hot.

    I have not updated my sig yet, but I have the Gigabyte P55A-ED3R board and an i5 750. I need to buy a cooler asap though as the stock cooler is a bit poo.
    Last edited: 21 Mar 2010
  6. tywyn


    Joined: 12 Jan 2009

    Posts: 122

    Yes the price of memory has shot up unfortunately, as I was thinking of getting another 4GB, but at those prices I'll be waiting some time :) I just checked my account and it was £74 I paid (£65 + Vat 15%)

    The high clock with a stable burn test I've been consistently able to achieve so far is 3973Mhz.

    198 x 20
    Vcore 1.4V
    IMC 1.275V
    Dram 1.65V

    Think I'll try 21x with a lower BCLK.

    I'm not an experienced O/C, so I wondered after a few weeks after the chip has been running at 3.9Ghz would I be perhaps able to attain 4Ghz after a 'wearing in period' for the chip?

  7. PaulyD


    Joined: 24 Mar 2008

    Posts: 4,636

    Location: High Wycombe

    No wearing in period..

    Would try 190x21 first, a lot of chips dont like the even multi's and run cooler (at less volts) on the 21x multi
  8. rumble291


    Joined: 4 Mar 2010

    Posts: 139

    Trying upping the voltage on the ram if you are overclocking that aswell. Mines DDR3 running at 6-6-6-20 at 1.78v with an overclock from 667Mhz to 750Mhz stable.

    Keeping upping the volts until it runs nice with no errors. If you add too much voltage to the RAM you will hit issues aswell! Like I found out a week ago lol. 1 notch determines stability with my setup.
  9. vocch


    Joined: 1 Aug 2005

    Posts: 723

    Location: Not far from you!

    Your system is AMD so your tips do not apply to an intel system as 1.65v on the memory is MAX any higher will fry cpu.
  10. Hotwired


    Joined: 17 Aug 2009

    Posts: 8,980

    Here's my settings:

    CPU: 750 @ 200x20
    RAM: 4GB 1600MHz 7-7-7-24 2T (yes it's that awesome £74 GSkill from last year)

    CPU Voltage: 1.35625V
    CPU PLL: 1.80V
    RAM Voltage: 1.60325V
    IMC: 1.20575V

    I'm normally lurking on 3.4GHz but I had a go with IBT on 4.0 just to have a check.

    The difference between Prime95 and IBT is pretty extreme, at 4.0GHz I'm getting 68-69 on IBT but on Prime95 it's 56-58.

    10 degrees difference :eek:

    Cooling is my H50 + extra fans on "loud".

    1.2anything on the 750 was a no go in a 5 pass "High" IBT same with 1.3.

    1.35625 worked fine for a 20 pass, CPU-Z manages to find a few more microvolts in there and reads CPU voltage as between 1.36 to 1.375 so take that as whatever you will. BIOS setting is 1.35625.
    Last edited: 29 Mar 2010
  11. tywyn


    Joined: 12 Jan 2009

    Posts: 122

    I've tried various settings and multipliers, but it fails to get consistent passes in the burn test on anything over 3.8Ghz. The settings have been as high as

    CPU Voltage: 1.4V
    IMC: 1.35V
    RAM Voltage: 1.65V
    CPU PLL: 1.90V

    but it still fails the burn test. I've been trying since Friday, so will give up on it now.

    My settings for a stable 3.8Ghz are

    190 x 20

    CPU Voltage: 1.35V
    IMC: 1.25V
    RAM Voltage: 1.65V
    CPU PLL: 1.80V

    It doesn't got over 58c in BFBC2
    Last edited: 23 Mar 2010