Very Strange Memory Problem!?

[RubinRemus]

Hi all, Just joined up

Apologies up front for a rather long first post!

Whilst not at all new to PC's (having worked on them for quite a number of years now) I am becoming baffled by this one:

Asus M4A78LT-M board.
AMD Phenom II x6 1090T BE CPU (3.2Ghz)
4x Elixir 2Gb DDR3 RAM - M2Y2G56CB8HC5N-CG (8Gb total)

Everything is stock standard.
CPU = stock 3.2Ghz
RAM = 1333 1.5v

Now here's the problem:

With 2x 2Gb sticks installed in A1 + B1 slots, everything is hunky dory.

With all 4 sticks installed, I don't even get a POST beep.
Absolutely nothing...black screen.

If I mess around with some settings, I can get it to run with all 4 sticks.
I tried adjusting the memory voltage up to 1.56, 1.59, etc.
I attempted to add a 9-9-9-24 timing, although the mobo's BIOS is fantastic for tweaking - dozens and dozens of settings, a lot of which (for memory) I cannot find the correct settings for. So just added the usual 9-9-9-24 timings and left the rest of the options on auto.
I have tried running the RAM at lower clock speeds - it runs fine.
I have tried higher (800) but it won't run.
So, it's usually left at 667.

Eventually, I have it running on all 4 sticks.
It will run all day.
I can run Phoronix benchmarking suite all day, through the various tests.
I can run Memtest+ perfectly well.
It will reboot fine, over and over.

However, if left off overnight, I can return to it in the morning and we're back to square one!
No POST. No nice Beep!

If it remove 2 sticks, going back to just A1 + B1 slots again, all is well.
The configs are still held in the BIOS from before.
I drop everything back to "auto"
Reboot.
Start applying changes again.
Add the other 2 sticks and eventually have it working again.
This can sometimes take quite a few attempts but it gets there in the end.

Untill it's left overnight, turned off, again.
(By turned off, I just mean simply powered down in the usual manner. PSU still plugged into mains supply, etc)
Bear in mind, it is *not* losing my BIOS tweaks. They are still present the following day.

I cannot seem to find much info on the RAM sticks - correct timings, etc.
A full set of timings/settings for these sticks would be wonderful.

If anyone can offer any insight into this, or any kind of advice, suggestions, all will be very gratefully received!!

Many thanks

 

[joxang]

If memtest is completely fine then it sounds like a motherboard issue (e.g. a dying memory slot).

Forget tweaking settings, set everything to bios defaults. Try changing the mobo battery first (unlikely to help but easy to do). Then try to pinpoint a damaged ram slot - will machine boot with three sticks inserted into different slots?

Booting whilst tapping escape skips the bios memory check, though if a memcheck comes up positive you should get long error beeps.

 

[RubinRemus]

Thanks for the suggestions

It will boot with 2 sticks in either A1 + B1 Or A2 + B2 combinations.

I *have* had it work with 3 sticks but that is just as intermittent as with 4 sticks.

Given that it will work fine with 2 sticks in either A1 + B1 *or* A2 + B2 does that mean that each slot would be proven to be OK?

It appears to be *completely* reliable in either of these configurations too.
i.e the left overnight thing isn't an issue with the 2 stick configuration.
(Although I could test this further)

Also, regarding POST codes, with the 4 sticks installed (when not working) it does not even attempt POST.
There are no error beeps, etc. Absolutely nothing - i.e. power up ---> lights on ---> fans spin up ---> HDD spins up ---> no VGA signal at all ---> no POST/error beeps.
But then, another time, it all works fine!?!?

BTW, it has *never* worked with all 4 sticks with everything on "auto" in the BIOS.

Some other thoughts, although it's completely possible they are "red herrings";
I have read of some mobo's running 2x matching sticks fine, but not liking 4x matching sticks at all. I cannot ascertain the exact reasons for this, or if there is any way of checking if this is specifically the case and using a different brand/type of RAM would cure it?
I do not think these Elixir sticks are on the QVL.

Again, all input gratefully received


EDIT:
Further testing in single steps -

• Slot A1 only - Works fine
• Slot B1 only - Works fine
• Slot A2 only - Doesn't seem to like it
• Slot B2 only - Works fine so far
• Slots A1 + B1 - Works fine.
• Slots A2 + B2 only - Works fine.
• Slots A1 + B1 & A2 + B2 - This is where the problem is!

Having said that, I'm not sure A2 or B2 are supposed to be used on their own, are they?
In single stick configuration, wouldn't A1 or B1 be used?