Intermediate no video signal that I fixed, but it had me confused (opinions very welcome)

[Frankie]

So I was fixing PC that didn't wanted to boot. Did the usual, hooked up the HDD to my pc via dock, checked with Crystaldisk and a lot of reallocated sectors showed up. You would think to get a new HDD, install win, done, right ? Nope.

 

I also wanted to be thorough and check PSU with tester just in case, it was on the higher side on the 5V rail, but nothing major. Hooked it back up to the MOBO and that's where it started. No video signal at all. Couldn't get it to work. So I went all out, MOBO out to check for shorts, reseat the CPU, nothing. Then I switched RAM stick from one DIMM slot to the other and it posted just fine once, then it didn't wanted to and then it worked again. So I did a little read up on it and a lot of problems like that could be BIOS related. So I flashed the BIOS to the newest version, posted multiple times just fine after that, so I tried to switch it back up to the original DIMM slot and so far it went through win install and a lot of restarts and ''cold starts''  just fine, like nothing ever happened.

 

It did confused me a little bit, so only thing that make sense to me is that for whatever reason BIOS started to have problems with recognizing the first DIMM slot and worked just enough with the second one to work so I could fix it up with flashing new, updated BIOS version, that fixed it. If anyone more experienced than me could chime in and either confirm my theory or post opinion I would very much appreciate that.  P.s. Memtest86 went just fine with no problems or errors.

 

TL:DR - PC had a intermediate problem with no video signal, switching RAM from first DIMM slot to second one worked enough to flash new BIOS and get it working. After that switching RAM to the original DIMM slot woked again, so probably more of a software problem than a HW one. Not exactly sure, asking for opinions.