Since some time my PC gives (3 beeps, pause, 3 beeps, reboot) repeatedly on boot. Nothing on the screen. Googling for this beep code gave me no meaningful results (it's certainly not a keyboard problem). After many (around 30) tries of booting, it sometimes gets through and then I can use my PC for days (without powering down) without a problem. But once a few days my screens are black, keyboard lights frozen. After restarting my PC, I'm again faced with the boot issue.

My first though was that it is a GPU problem, as I could boot when I removed my GPU and used my motherboard video. However, that seems to have been a fluke.

Today removing the GPU didn't help as well and I started investigating further. I removed all devices attached to my PC. I unplugged all SATA cables (I don't have an M.2 SSD), removed my GPU, used a different PSU and removed 2 of the 3RAM sticks, changing which one of the 3 I used. I did a CMOS reset and used a new CMOS battery. I still couldn't boot, with the same beep code.

I plugged everything in again and started the boot loop. After about 20 minutes the PC finally booted successfuly. After confirming the UEFI default settings, and a rather long boot, Windows started without problems.

So... that's the current situation. I can use my PC but I'm afraid of rebooting it or powering down for any reason.

I guess it must be something related to the motherboard or CPU as I ruled out virtually everything else.

I can just buy a new motherboard and CPU (and probably RAM, because this one is still DDR3), but it would be nice to know what happened.

Any ideas?

My hardware:

Summary Operating System Windows 10 Home 64-bit CPU Intel Core i7 4770 @ 3.40GHz 41 °C Haswell 22nm Technology RAM 24.0GB Dual-Channel DDR3 @ 790MHz (10-10-10-30) Motherboard ASRock H87M Pro4 (CPUSocket) 34 °C Graphics IPS235 (1920x1080@60Hz) D2343 (1920x1080@60Hz) DELL P2412H (1920x1080@60Hz) 2047MB NVIDIA GeForce GTX 660 (ASUStek Computer Inc) 34 °C Storage 232GB Samsung SSD 840 EVO 250GB (SATA (SSD)) 31 °C 931GB Seagate ST1000DM003-1ER162 (SATA ) 29 °C 931GB Samsung SSD 850 EVO 1TB (SATA (SSD)) 30 °C Optical Drives No optical disk drives detected Audio NVIDIA Virtual Audio Device (Wave Extensible) (WDM)
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1 Answer

From the text dispersed here and there, I'd guess the culprit is on the motherboard, seems to work as the MoBo warms up a bit... so a broken PCB-trace, possibly. One might need quite advanced tools to find (=locate) the actual problem.

One step further, and a possible problem removal step:

  • It isn't just the RAM modules: The RAM needs to have working communication via the databus and memory access/control lines (RW, CS, and all that), from RAM to CPU and vice versa.
  • Use a pencil eraser - lightly - to erase the oxide (air oxygen induced "contamination") on the RAM module contacts.
  • Get some "contact spray" from an electronics supplier (note: nothing else than that!) and spray it on the CPU-socket and RAM module connectors (on MoBo and modules)

... you might solve the problem by those two steps.

I have removed strange effects on old computers by very similar methods. Old oxidized connectors will not allow current to flow as freely as required for correct function.

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