I have the same problems:
4 * 4GB Corsair CML16GX3M4A1600C9 runs ok with 1333MHz but fails with XMP 1600 Mhz or manual 1600.
The DIMM modules worked on BIOS 0028 with XMP 1600Mhz. BIOS 0037 even once failed to boot (POST code 20) until I removed and re-inserted the DIMM modules in a different order. This seems to trigger a re-init of the memory timing algorithm.
How many DIMM modules do you have? Does 1 or 2 modules work @ 1600? (didn't try this myself, got tired of troubleshooting)
Did you check if your CPU reaches turbo clock rate when doing a stress test with 8 threads? Mine stops at 3.8 Ghz (I have a i7-2600K).
Some threads on this forum claim that increasing the voltage of the Processor System Agent to 1.2V helps to get the memory stable (especially when a lot of DIMM modules are used). On my system it seems to have no effect.
Which hardware revision does your board has (the AA #). G30742-403 has additional resistors for improved DIMM voltage control by the MRC.
By the way which CPU does your system has (with core 2th gen the memory controller is build-in)?
I had the same experience with 20 error code, and succeeded to boot
just after removing my DIMMs and installing at the blue slots, instead of the black.
My DIMMs are G.Skill 1333Mhz 7CL.
The only thing I can't understand, is how removing the BIOS battery,
resting with a jumper and turning off my PSU, won't reset these
DIMMs at the original place they were installed originally.
It shows again "Error 20" and the 6th led is blinking in green.
What a shame!
I have 2 DIMMs (same corsair stuff what you have) and another OCZ 2 DIMM set. Doesnt matter what configuration I tried - only 1333MHz seems to work normally.
I have been playing around with i7 2600 non-K, so all overclocking done is via Turbo Boost which gives me 4 additional bins to go per core. This works correctly with 036 and 037.
Turbo Boost behavior is normal both ways: default and +4 bins per each core. Stress test with 8 threads activates Turbo Boost as it should same applies to 2 threads etc.
My board is ***401 revision.
Prime95 is still a decent stability test, but there are better ones out there. If you want to test all of your RAM download and run LinX. This program also beats the hell out of the CPU so it's closer to OCCT stress than Prime95 stress.
Unfortunately, though I thought my board is clean from this horrible error 20,
last night I've put my Pc into sleep (As I'm doing every night and during the day.
When trying to wake it up, there was not video or keyboard signals, and AGAIN(!!!)
error No. 20 is shown on the board and the 6th led from the left is blinking.
I really don't know what to do. This board was replaced twice. I haven't changed
nothing yesterday night. Something with this board is terribly wrong. I'll contact Intel support again. Though it cost me a lot of money to ship it to Europe every time, they may think I'm causing this by my self as they are not aware of the so many people that suffering from this 0035 BIOS issue.
I'm very close to give up, but I've paid $220 for this board! Why Intel can't find a solution for this issue for almost 5 months now?! I haven't enjoyed my new Pc because this board. I lost a lot time, work and money.
"Vbaderks" has mention rev. 403 added additional resistors for DIMM Voltage reference: http://communities.intel.com/message/163666#163666
Mine is 402 (original was 401) but they both having the same issues.
Does anyone suffer this "20 Error message" with 403 rev.?
Btw, my DIMM modules are 1333Mhz, so I'm not sure the cause is 1600Mhz DIMM as some said here.
I am having the POST Code 20 come up on mine sometimes, but most of the time is is the POST code 59 for Resetting the USB Bus. I have already contacted Intel about it and they are going to RMA this board. It is the second one, and yes it is the 403 version. I keep having issues with this board and the watchdog resetting during POST and now this. I can not get it to go to Recovery Mode BIOS or do a Emergency Flash (Pulling the Jumper). Funny think is that with the watchdog going off during boot is that I don't even have this thing OC'd. It is all stock. Going to try a third board and see what happens. May have to find a new board from another Manufacture.
DZ68BC Version 403 BIOS 0037
Intel i5-3570K (Non-OC'd)
Corsair Vengeance 16GB RAM Kit
Corsair HX750 PSU
WD Caviar 320 GB HDD
I also have a second replacment from Intel, and after a monthy and a half, my board went to 20 Error Code and won't boot. Also 6the th led from the lest is blinking continueslly. I've upgraded my board to 0035 BIOS upon receiving it, and it went into 20 Error Code emidiately. Somehow I could recover it and make it to boot, but after a month and a half, 20 Error Code came back without any warning and I can't recover any more. I havn't changed any BIOS settings or any hardware. Now I have to RMA for the thierd time, but it seems it won't help as well. The only BIOS has worked until now is 0028 ver., so you may want to ask Intel to have a board with this ver. and not upgrading it in any case. This is WIERD to buy a $220 value board without having any option to upgrade a BIOS.
Sorry I was mistaken, I did have a Ver 402 board. They told me that they were going to give em a 403 the last time but they didn't. As for upgrading the BIOS, unfortunately I have to upgrade it since I am running a 3rd Gen CPU. The board is on the way to Intel as I type this on an over night trip, so hopefully I will have the new one by the beginning of next week to see if the problems still exist. If so, I may just switch to a 2nd Gen CPU get a different MB.
I talked to an Intel Desktop support tech Saturday, and they assured me that all the problems that most people are having with this board are with it clearing the OC settings. So I guess they haven't even paid attention to this forum on their own site, with tons of people have more issues with it than just getting their OC settings cleared. I , myself have RMA'd this board twice for the same reason, both times it would not show any video on the screen and would beep twice saying it didn't detect a video device even though my monitor was plugged in. This last time I was able to re-flash the BIOS and it worked for about 2 weeks and now I am getting the POST codes 20 and 59 showing up and it won't complete POST, and I can not flash the BIOS at all now.. This may be the last time I buy an Intel board.
Well I guess as Namrur has said, the only option is to use this board with a Gen 2 CPU and keep it at BIOS 028 or earlier. It still baffles me though that Intel has let this get so out of hand and they don't even have the guts to give us some valid information or assurance that they are fixing it. They just act as if it isn't going on. With the 15 years that I have been in this field, Intel has always been on top, but now it looks like their pedestal is falling apart, and they are on the fast track to the bottom. As for the RMAs, I agree with you, and for what it costs to send this things back in every time, we could be using that money to buy ASUS boards. This is the last time I RMA it. If it fails this time, it is going in the damn trash.