Question Half of motherboard DIMM slots not working

Nov 13, 2020
Putting the following build together:
Asus rog strix b550-f wifi
16gb (2x8gb) 3600mhz cl16 RAM dual channel kit

Of the 4 DIMM slots, B1 and B2 are not working. No system post and DRAM QLED is lit.
After much trial and error, both of the sticks work standalone in either slot A1 or A2. Both stick work together in A1+A2 but run in single channel mode.
Neither of the RAM sticks work in any of B1 or B2 on their own, or any combination using any of B1 or B2 slots together with A1/A2.
BIOS is updated to 1212 version.

I have not yet tried CMOS reset or checked the CPU pins. (The CPU came pre-installed on a pre-flashed motherboard from a vendor).

Im thinking this is a motherboard issue, and I should RMA it. Any other thoughts?

Many thanks.


Memory placement for two sticks as follows, 2nd and 4th slot from cpu.

If you still cannot post with ram in slots described above, there may be a bent cpu pin by the person installing the processor.
Last edited:
Recommended slot for 1 DIMM in single channel mode is B2.
Dual channel mode with 2 DIMMs is B2 + A2 as per your manual page 1-5.

PLease list the P/N of your RAM kit to check they are a tested kit and listed on the MB QVL.?
What changes have you made in Bios since RAM installed ?
Go into your Bios and clear to default settings.

It would appear the MB is faulty from your description however eliminate the possibility of a faulty DIMM by testing with Memtest86 on each module in the slot that works.

If all DIMMs check out OK and error free then RMA the MB.


May 10, 2015
So many questions that simply won't find answers here.. i myself have the exact same problem like you, can't run dual channel since combo channels of the same color are dead, and people without real knowledge or disinterest can't give you usefull advice.

i recommend you the following steps to do, maybe it helps in finding the problem or helps to better understand w to do, that is, if you are able to do these without hurting yourself or your electronics.

- Test each RAM separately, pick 1 ram and test all four channels, see which one works and which don't, then pick your other memmory module and again test all 4 slots.

- Make a VISUAL Check for BENT/BROKEN PINS on your MEMORY SLOTS ! attempt repairs if found anything.

- Take out CMOS battery/Reset BIOS to defaults.

- Dissasembly your motherboard, and take off your cooler and carefully take out your CPU, check for broken/bent PINS. ( Is possible y have bent pins, which i doubt, specially if it worked for a long time and y haven't touched it, but y never know )

- Motherboard
might have been bent from your CPU Cooler because tightly screwed together, damaging circuits therefore not making contact properly, try screwing it back slowly, and boot w damaged ram slots, screw it slowly, stop and boot, check if it works, until u can't screw it no more, but BE VERY CAREFULL, i don't know what cooler y have, don't tighten it too much.

- Power OFF machine,
take a very thin screw driver or something that fits in the memmory slots, put some COTTON w a little alcohol on it, and try to CLEAN the inside of your pins.

in worst case, your chipset is broken/damaged, or something else on the board, if you still have warranty i HIGHLY recommend sending it back.
Nov 13, 2020
Thanks all for your notes.

The P/N of the RAM is
  • TDPGD416G3600HC16ADC01
I dont see this on the QVL on the asus motheboard support website.

I have tried each stick of RAM in every DIMM slot, B1 and B2 slot do not work under any combination. The DIMMs themselves work fine in A1, A2 slots. I am typing this from booted into windows on the machine in this configuration. CPU-Z reads 3600mhz memory speed 16gb appropriately.

The motherboard came pre-flashed to latest beta bios, I did not change any settings on it initially and the issue was there on purchase. I changed the BIOS post discovering that A1, A2 worked to enable the D.O.C.P. After this I tried the B1, B2 DIMM slots again but still no post.

The parts are all brand new and received from vendor yesterday - I can return or RMA them and it should all be covered. I will need to speak to the vendor first before attempting these steps above to ensure I dont void any warranty.

Thanks again