Asus motherboard iv extreme. Q CODE originally 6A and now 3B.

Hi everyone,

I am having trouble in diagnosing a computer that I am trying to fix for a friend. When I turn on the machine nothing displays on the monitor and I am presented with the q code 3b. The code 3b according to the asus manual means Post-Memory PCH initialization is started. I would really appreciate any help with solving this.

The Specs are as follows.

CPU: i7-2600K - CPU was never overclocked.
GPU:GTX 570, I have tested with a working gtx 770 and same result. I also tried without the GPU using integrated graphics and again same result.
RAM: DDR3 2133 Mhz G-SKILL 2 * 4GB.
PSU: Enermax revoution+ silver 1044W.

Initially when I first received the computer, The q-code was 6A "system agent DXE SMM initialization is starting". I contacted asus (the product is out of warranty) and they informed me that this revered to a core component of the machine to be faulty - The RAM, CPU or CPU Socket to be precise. I removed the PSU from the machine and performed the fan test using the paperclip method. The fan on the psu started to spin no problem. I then decided to rebuild the entire pc from scratch. I removed the cpu from the socket, checked the cpu for any scratches or marks. There was none and also checked the socked. Both the CPU and socket looked brand new. I applied new thermal paste and fitted the cooler back onto the motherboard. Next I flashed the BIOS to the latest version using the BIOS Flash feature found within the board and cleared the CMOS using the button as well as removing the CMOS battery, clearing and reinserting the battery. All the fans run and leds light up as expected.

I then placed in the two ram sticks into their relevant headers and booted up the machine to receive Q code 3b. 3b refers to Post-Memory PCH initialization is started. According to online forums this refers to the RAM or the GPU. Could both RAM sticks be faulty? Now I have tested another gpu on the machine that I know is working and I have also used integrated graphics and again it's the same result. Code 3b appears on all accounts. I have also tried alternating the 2 sticks of RAM around in the slots as well as one stick at a time and I am getting the same result. Just to be sure I removed both RAM sticks to see would the q code change and indeed it did. The code was 22. I reinserted the ram sticks and 3b returned.

I have also observed on the motherboard a number of small onboard LEDs that refer to the voltages on the machine. The CPU Led is green which to me highlights that the CPU is okay but this is not certain. The DRAM Led is yellow highlighting high voltage. I will be getting ram from another friend tonight and will try those sticks and will keep you updated.

If the RAM is not the issue, has anyone experienced this before and is there something I am missing that I should test? Unfortunately, I don't have access to another cpu or motherboard so if I want to test with these I will have to buy them and I don't want to put a lot of money into an old system. I still want to get to the bottom of it as it's eating me up.

Thanks for all your help.


UPDATE: I checked with my friends working RAM sticks that are compatible. Will be getting a PSU tester at the end of the week and will test the PSU fully.
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