Getting 8GB of OCZ PC6400 DDR2 to work with my XFX 750i SLI motherboar

Ok. I have an XFX 750i Motherboard model MB750IP29 and i bought 4 @GB sticks of OCZ PC2 6400 Part# OCZ2N800SR4GK and the timings listed on the heat spreader is 5-4-4 @ 2.1v. I can 2 sticks in slots 1&3 (dual channel mode) just fine. I have overvolted the DIMM slots through BIOS to 2.1 from the 1.8 factory default voltage. If I add a third stick to slot two the motherboard boots through BIOS and BSODs at the windows 7 startup screen. I can adjust memory timings manually through BIOS but have no clue on earth what each one means or does so I have left them all at auto. If I add all 4 sticks it just sticks on a black screen during initial boot and wont even begin to load windows. I have tried overvolting the DIMM slots to 2.3 because I read in another article in these forums that might solve a similar issue someone was having. I paid $200 for this RAM and would greatly appreciate the anyone that could help me to get it running. I'm somewhat new to the intricacies of memory timings and BIOS adjustments but i DO know that even with all 4 GB installed the motherboard is still only going to recognize 7GB. I'm ok with that....but as I've said...I would GREATLY appreciate any help!!!!!! thx :D
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More about getting pc6400 ddr2 work 750i motherboar
  1. correction....after running CPU-z the correct OCZ part # is OCZ2N800SR2G
  2. Using DDR2-800 modules that require 2.1V to achieve 5-4-4-15 timings will be very difficult to get stable when installing more than 2 modules. Try 6-6-6-18 timings to see if it will help. According to OCZ, you are not supposed to exceed 2.2V.

    It's a lot easier when using modules like the G.Skill PI Black http://www.newegg.com/Product/Product.aspx?Item=N82E16820231209 that only require 1.9V at 4-4-4-12 timings.
  3. icarusisaacs said:
    correction....after running CPU-z the correct OCZ part # is OCZ2N800SR2G

    The EPP profile is 4-4-4-15 1T. Did you select it in the BIOS? If that doesn't help, just increase the timings as I suggested and keep the voltage at 2.2V maximum.
  4. ok....which values get 4-4-4-15?...the 1t/2t is easy enough....i have several more values than 4 that i can adjust ranging from anywhere from 2 to 30.....let me look at the order they are in in BIOS anbd ill post....but thanks for the help so far....u dont know how frustrating this has been since ive never fooled with such things before....anywho, ill post the timings i have in one sec
  5. The first 5 all are in that order in the BIOS. Leave the rest of them at Auto.
  6. ok.... according to nvidia control panel my current timings ( and im pretty sure i can adjust all these in BIOS are as follows:
    tRAS: 18
    tRCD:6
    tRP:6
    tRC:24
    tWR:5
    tRRD:3
    tRWT:5
    tWTR:10
    tRDRD:3
    tWRWR:2
    i also have a couple more that may be adjustable in BIOS but are greyed out in nvidia CP..
    they are..
    tFAW:
    tWRRD:
    tREF:
    once again....thx....and i swear man...if u get this worked out with me i'll paypal u $50.....seriously
  7. It looks like they are running at 6-6-6-18 2T and they are not stable? You should use the $50 to get modules that are certified to run in your motherboard. Again using 4 modules sometimes is challenging (though I never ran into issues).
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