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4770K/Z87: Very bad performance at high memory clocks

post #1 of 5
Thread Starter 
Weird issue: Setting my RAM to run at 2600 MHz or higher, memory read, write and copy bandwidths will just plummet. At 2200 MHz I get around 34 GB/s, at 2600 MHz it will be down to to 26 GB/s and then rise to 28 GB/s at 2800 MHz. Can't go higher than that.

2400 MHz won't boot with CPU OC, without CPU OC the read bandwidth will be good, but write and copy will be crap already.

I tried using only one channel and only one DIMM, but that only yields half of the bad performance. Also tried with and without CPU OC. Verified primary and secondary timings to be correct. I also tried increasing DIMM, System Agent, Analog and Digital IO voltages, but no change. Even did a CMOS reset, loaded XMP and set auto everything.

Using an i7 4770K on an ASRock Z87 Pro4 with Team Xtreem LV 2600 MHz CL10.
Edited by Rezal - 10/15/13 at 10:04am
post #2 of 5
Huh, no change even with higher voltages might mean that your CPU's IMC might be weaker than most. There's really not much that can be done other than get another 4770k and hope the silicon lottery is nicer next time.
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post #3 of 5
Thread Starter 
Issue solved: My mobo set tRDRD, tRDRDDR and tWRWR too high at these dividers, which apparently completely screws your bandwidths. Reducing these timings manually improved the bandwidths by more than 50%. Too bad my mem controllers don't quite like 2600 MHz, but 2500 definitely works.

Might try 2600 MHz with lower CPU OC some other time,
post #4 of 5
Quote:
Originally Posted by Rezal View Post

Issue solved: My mobo set tRDRD, tRDRDDR and tWRWR too high at these dividers, which apparently completely screws your bandwidths. Reducing these timings manually improved the bandwidths by more than 50%. Too bad my mem controllers don't quite like 2600 MHz, but 2500 definitely works.

Might try 2600 MHz with lower CPU OC some other time,
Yeah, that'd do it too. Try tweaking around to see if you can pull that last 100mhz out of the ram.
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post #5 of 5
Thread Starter 
Will do that tomorrow. I actually got 2533 (2666 with BCLK 95) stable without raising System Agent or IO voltages.
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