Hi r/techsupport

Hardware configuration:

PCPartPicker Part List

Troubleshooting:

I've been using this PC for the past five years without having any major issue. Usually the PC is either running or sleeping, so I very rarely turn it off completely. A couple of weeks ago I turned it off completely. After turning it on again, the PC didn't POST anymore. The only thing that happens is that the CPU fan is spinning for about 20 seconds after which it slows down and starts spinning again. There is no video output or any other sign of living except the spinning of the CPU fan.

I started troubleshooting by removing the GFX and all RAM DIMMs. I connected the display to the onboard HDMI outlet and started installed one RAM DIMM in slot 1. I powered up the PC and it was booting normally. I continued to test each DIMM in slot 1 and every time, the PC would boot normally. I continued to test all DIMMs separately in the remaining 3 slots and every time the PC would boot.

After the last test, I installed the remaining 3 DIMMs and the PC wouldn't boot anymore. I removed the DIMMs one by one in reverse order, each time testing if the PC would boot - but it wouldn't. I ended up with one DIMM in the last slot, which was working previously, but now it wouldn't boot anymore.

Actual issue:

Using only one DIMM, the PC wont boot unless I move the DIMM to a different slot. Removing and inserting the DIMM in the same slot will not fix the issue. Removing the DIMM and inserting a different DIMM in the same slot will fix the issue. It does not matter which slot is used, the behavior is always the same. The issue does not appear when restarting or putting the PC to sleep.

I did the same test with a different set of memory (https://pcpartpicker.com/product/hNtCmG/kingston-memory-kvr13n9k216) without any difference.

I tested all DIMMs with memtest86 without detecting any issues.

I found two posts with similar issues:

https://superuser.com/questions/422483/switching-ram-modules-fixes-boot-hiccups-why https://www.dell.com/community/Optiplex-Desktops/9020-tower-wont-boot-unless-i-add-remove-memory/td-p/7350520

Both solutions don't seem to apply to my problem.

I'm at a complete loss, any help is appreciated :)