Strange Asus Z170-A memory config

[petemanuk]

Hi,
I’ve got an Asus Z170-A motherboard that supports 1 or 2 or 4 DDR4 memory Channel configs.
It has memory slots DIMM_A1,DIMM_A2, DIMM_B1, & DIMM_B2.

The manual says you can have:

Singe channel using DIMM_A2
Double channel using DIMM_A2 & DIMM_B2
Quad Channel using slots DIMM_A1,DIMM_A2, DIMM_B1, & DIMM_B2.

The only combination I can get the board to boot with is single stick in DIMM_B2 or two sticks in DIMM_B2 & DIMM_B1 ?? According the to manual this configuration shouldn't be possible.

I’m using four matched DDR4 ram stick which I know defiantly work but just to check have use another matched set just in case also used a couple of different known good cpu’s with same results

Any help would be much appreciated.

[SMDFlea]

Re: Strange Asus Z170-A memory config

Any help would be much appreciated.

Do you have the latest bios installed, you can check the release notes for each version and see what changes have been made, like improving RAM compatibility

[petemanuk]

Re: Strange Asus Z170-A memory config

Thanks for info.

Yes tried that still the same

[piernov]

Re: Strange Asus Z170-A memory config

Hi,
The only combination I can get the board to boot with is single stick in DIMM_B2 or two sticks in DIMM_B2 & DIMM_B1 ?? According the to manual this configuration shouldn't be possible.

All combinations are possible, but not necessary optimal. Recommendation is generally to populate first the furthest slot of the closest channel to the CPU, since in theory this allows getting the best timing and signal integrity, but that doesn't really matter.
Boards are laid out CPU | A1 | A2 | B1 | B2, so furthest slot (2) of closest channel (A) is indeed A2.
But populating only B1 will also work fine.
Of course to get dual-channel to work you need at least one stick in each channel, if you put 2 sticks in the same channel and none in the other you don't get dual-channel.

An entire channel being dead is most often caused by damaged pins in the CPU socket.

[FZG]

Re: Strange Asus Z170-A memory config

I once owned that Motherboard and it also had strange behaviour related to memory. I originally used it with an i5-6600K and 4x8GB RAM, everything was fine. Then I upgraded to an i7-7700K and suddenly only half the RAM was detected. Changed the RAM, even suspected the new CPU and had it replaced under warranty... nothing changed. It was some incompatibility between the board and the (officially supported) CPU. So my question is, what CPU are you using and what RAM?

[DynaxSC]

Re: Strange Asus Z170-A memory config

See next.

[DynaxSC]

Re: Strange Asus Z170-A memory config

You might have a bad contact from the memories to the processor due to:
a) bent pins in the cpu socket
b) dirty pins of the cpu socket (eg invisible thermal paste residues, ar fat from the fingers)
c) dirty contacts on in the dimm sockets
d) oxidated contacts of the dimms
e) missing coupling resistors on some of the dimm (usually 15 ohms)

First check booting with only one dimm inserted into all the sockets one by the another. Normally board should boot in all the 4 dimm sockets and one dimm w/o a problem, bios may have complain, but this is not important.
If at least one slots is not working, then this lot has a contact problem (somewhere between memory and CPU), and will prevent booting completely, if this slot is used.

For CPU socket examine it visually for bent pins, and straighten them if you feel able to do this - I use for it 10x magnifier glass and a very small watchmaker flat screwdriver - this must be done really very carefully, as bending a pin to much will lead to breaking him (loosing elasticity), and then you will need to exchage the pin, or the whole socket. Also pay attention to not bend other pins, it's much easier to happen than you may imagine. The memory contatcs are always on the ca half side of the socket near the dimm sockets. Clean the socket contacts with a very soft brush and isoporopylic alcohol - move the brush very gently in diretion of the pins, never against/aside, don't use force, clean the rest of the alcohol with a compressor (keep min. 20 cm distance, max 8bar), or just by blowing with your mouth (in that case wait some 30 minutes so the alcohol can evaporate completely. You can reapeat this process 2-3 times. You can also accelarate evaporartion with a hairdryer.
Clean the dimm sockets same way as the cpu socket, here not so much care is necessary, also blow out the rest of the alcohol somehow. Residues of alcohol (in normally 99.9% clean) with not destroy anything, but they wiil prevent the board from booting.

The dimms check for mising coupling resistors with a magnifier glass.
Clean the contacts of the dimms with slight rubbing with a cloth and isopropylic alcohol, or with a contacts spray for electronics, but only via a cloth, use very low amout of the contact spray (put only a very thin film on the contacts). Pay attention not to rip off the coupling resistors, it's very easy to do this "successfully", and then only a hotair station can help to get them back on their place, provided you will find them

If you have done everythiong OK, then trying to moving the dimms during mobo opertions slightly to the side back and forth should not lead to mobo to hang, otherwise there is still not perferct contact.

[DynaxSC]

Re: Strange Asus Z170-A memory config

PS: CPU pads may also need to be cleaned.