Question C5 Memory Error - Boots But Doesn't Post for ASUS Motherboard

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Dec 28, 2019
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Recently just completed a Ryzen 3 build.

Everythings working, motherboard, GPU, fans spin, case lights work, power supply works, even the RAM lights up.

Only problem is, the computer won't post with the beep and allow me into BIOS.

I have an ASUS Zenith II Extreme (TRX40) motherboard with the following memory:

4 x 8GB G.Skill Trident Z Neo (F4-3600C18Q-32GTZN)
4 x 8GB G.Skill Trident Z Neo (F4-3600C18Q-32GTZN)
64GB TOTAL installed in 8 slots

and the error it comes up with is C5.

I've tried pressing the Clear CMOS computer on the rear IO with computer completely powered off and unplugged from mains power, but the computer still won't post.

Repeatedly pressing F2 and Delete key isn't working to get straight into BIOS either.

Two questions about this.
  1. Does anyone know what the C5 error actually is (I couldn't work it out in the manual)?
  2. Is the only alternative to pull each and every RAM stick out 1 by 1 to test each individually?
Interestingly, the website no longers lists 3600 memory (the speed of my memory) as compatible despite it being listed earlier and still being in the manual when I last checked.

I specifically remember this, so not sure why it's disappeared from the website.

I could see this being 3 causes.

Either I didn't install one or more sticks properly, one stick (which I unforunately dropped on a tiled floor) got damaged or 3600 memory is no longer compatible with the board.

Anyone else encountered this memory related error on a TR40 motherboard?
 
During the build, I had 3 instances where there was ESD zap. One instance on a case fan header at the back of the case, one where my hair made contact with the Front IO ports and one where I touched an exposed part of the GPU. None of this went to the motherboard, so I don't think its that.

Given this though, i'm afraid to use the power button on the motherboard in fear that i'll short it with ESD while on.

Given that I don't seem to be grounding myself properly 100% of the time, can harm be done to the PSU and/or other components if I shut down the PC while troubleshooting by turning the power supply off?

I suspect the answers probably yes, but i'm just trying to avoid touching the board as much as possible while in operation and I attempt to troubleshoot this memory issue.
 
what led's illuminate on your motherboard during boot up ?
Are both power connectors connected to the motherboard from the psu (8 pin and 24 pin) (2 different slots) ?
 
I checked the onboard LED next to the 24 pin ATX power connector. It comes up with an orange-like color closest to yellow which appears to indicate DRAM/Memory (manual says Yellow = DRAM, Red = CPU, White = VGA, Yellow/Green = Boot) is the issue which would be consistent with the large LED display on top the rear IO that says C5 followed by Memory Test.

Seems the problem components been isolated now, just need to work out specifically what's wrong with the memory causing the post to fail.

Will first try to remove/replace all memory (some may not be clicked into the slots properly).

If that doesn't work, then i'll test each module one-by-one as I unfortunately did drop one of the memory modules quite firmly on a tile floor (fell off the table).
 
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Ok so first thing you need to do is check your ram is in the QVL list of tested ram.
You may need to check what version your board bios is, you can get that by contacting asus support on their chat thing, give them the ppid number and they can tell you what version of bios the board was shipped with.
It might be possible that your ram was added to the qvl list after a certain bios update

next try 1 ram stick in 1 slot and reset cmos as you move it around the slots.

also make sure both power connectors are in, including the 8 pin cpu power plug
 
RAMs not on the QVL list, but i've used non-QVL memory before without issue.

I have removed all of the RAM sticks from the slots and noticed some clips were slightly misaligned. Wondering if it's just a case not all 8 sticks were clipped in properly.

In any case, I wanted to ask before doing tests of each stick 1-by-1.

Can I turn on the computer just for a brief period with nothing but the heatsink on top of the CPU with no CPU fan attached just for about 30 seconds or so to test ram? Or could this damage the CPU with no fan?

Reason I ask, is that it would be ideal if I can diagnose RAM issues without having to attach the fan as it'll be a real hassle at the moment having a nh-u14s-tr4-sp3 which is very large and covers up all the memory slots meaning i'd have to remove and disconnect the fan each and every time to test all 8 slots.

I'll do it though if necessary as a precaution.

Just don't want to risk damaging the expensive 3960x CPU I have in my build.

EDIT: I won't even take the risk, i'll connect at least the one exhaust fan just to be safe.

Then, the other four modules on the right will be easier to test with no fan.
 
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It wont post without any ram installed.
To save a lot of hassle, you could just try 1 stick in the default 1 stick slot.
Just because you have used non qvl mem in the past before doesn't mean it will work like that on any future boards.
I have just had that very same issue on a Prime Z930-A with non qvl ram.
The problem you have is trying to figure out if the cpu has an issue with its memory processor, or if the board has an issue with the ram slots or if the ram is not compatible with the board.
The easiest and quickest way to check this, is to buy a cheap slow 4GB stick from Amazon that is on the qvl list, clear cmos, insert it into the default 1 stick slot and with nothing else connected other than CPU and cooler, psu and ram (Eg no gpu, no drives etc) as barebones as possible start it up and see if it posts into BIOS. Red CPU LED followed by Yellow DRAm and then it should stop on a white VGA light. Then connect up the monitor to your onboard vga if the processor supports video.. If not then you need to connect up your GPU and hook the monitor in.

Dont do that until you get a white vga light
After that you should boot into BIOS and away you go
If it does then update your BIOS then try your expensive sticks in there, remembering to clear cmos first.
If you check the latest bios update info it will probably show a lot of dram compatibility patches.

Unfortunately for me, i managed to get my BIOS updated but still doesnt recognise the corsair ram i inserted, so have ordered some qvl ram

My bet.... its incompatible ram
 
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Boot successful after installing all 8 sticks again.

Able to get into BIOS, recognises the 64gb of RAM and CPU temps only around the high 30s.

Only problem now is I can't seem to set the boot priority so I can install Windows from USB drive.

Boot priorities option seems to be greyed out in BIOS.

Also can't seem to find XMP in the settings and ASUS's previous guide for updating BIOS leads to a dead link so there's some issues with documentation there also as the manuals not totally clear on how to update it without Windows being installed. But these are issues separate from this main thread topic which is resolved.
 
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