This May, I upgraded the motherboard, CPU, and RAM of my 7-year-old computer and my machine got stuck in a reboot loop. It always POSTed successfully (though sometimes it beeped twice) and loaded the motherboard’s splash screen, but rebooted right after the splash screen. The motherboard was a Gigabyte GA-F2A78M-D3H. The CPU was the AMD A6 6420K. The RAM was a single brand-new 8-GB PC3 12800 DDR3 “Desktop Memory Multi” from PNY.
I could enter the BIOS and change/view everything there. Whether I entered the BIOS or not, it looked like the system hung and restarted when trying to load the OS. After the Gigabyte splash screen disappeared, the monitor’s color changed from black to a sort of dark maroonish-purple color like it always had, indicating it was loading Ubuntu (the OS on my SATA hard drive). This was what it was supposed to do—except, y’know, not restart. This Ubuntu-ish color was displayed for 1 or 2 seconds. No text or anything else appeared.
This happened when I booted to the regular old SATA hard drive which was functioning in my previous configuration and which I had no reason to believe was faulty. It happened when I tried to boot to an Ubuntu live CD. It happened when I tried to boot to an Ubuntu USB stick.
The USB stick was the most “successful”: after the BIOS splash screen, some text along the lines of “Ubuntu 12.04” appeared for several seconds, along with a little keyboard and mouse icon. It looked like a boot disk should look. But then the system restarted after a minute or two.
This also happened when I unplugged the DVD drive from both the power supply and motherboard, when I unplugged both it and the HDD in order to boot to USB, when I unplugged the HDD to boot to DVD, when I unplugged all the other leads like the LED lights and USB lead. This happened when I inserted the RAM stick into slot #1 or #4.
When I unplugged both the DVD drive and the HDD from the mobo, it did not restart after the Gigabyte splash screen; rather, it told me no bootable drive was detected and would I like to enter the BIOS. Clearly, loading an OS was the fail point.
In the BIOS’s M.I.T. options, I saw that the right amount of RAM was detected, along with the right CPU of the right caliber. The CPU temperature was always around 37-40 degrees Celsius. I tried RAM slots #1 and #4 because when I initially inserted it into the slot that’s labeled 1 on the mobo itself, the M.I.T. status screen showed 8 GB of RAM in slot #4 (and nothing in the others). Then when it was in the slot labeled 4, the M.I.T. status screen showed 8 GB in slot #1 (and nothing in the others). So, I don’t know, maybe there was some mislabeling by Gigabyte, but I doubted the RAM was a problem. Both the CPU fan and the case fan that came with the case spun just fine.
Finally, I should mention that the reason I was upgrading my PC was that I assumed my old motherboard or CPU was dying, because even though it (usually) booted into Ubuntu just fine, the computer couldn’t handle even the slightest resource-heavy task. Just opening Firefox, for instance, caused an instant reboot.
I gleaned from the internet that a dying mobo was a good bet, though a failing PSU could also have been the culprit. I wasn’t completely sold on the dying mobo explanation because I saw nothing like this on it. My new configuration was of course only partly new: it had the same old 7-year-old PSU in the same old 7-year-old case. In my old system, to try to diagnose its problem, I ran a memory stress test from the BIOS—actually, two of them: one for a couple hours and one overnight. Both times, the PSU seemed to handle it, because it didn’t fail or restart or anything, so I assumed the PSU was working fine. The old computer could remain on for a few days, logged in to Ubuntu doing nothing, so I don’t know if that means the PSU was fine or if it was merely strong enough to handle idling but wasn’t strong enough to handle the more resource-heavy task of powering a new, improved mobo and new, improved CPU.
My new motherboard’s BIOS has no option for a RAM stress test—believe me, I looked everywhere four or five times. Kinda sucky. I would have liked to rule out defective new RAM before buying a new power supply, but I knew of no way to do that.
So I bought a new power supply and that solved every problem.
Actually, I bought a new case that came with a 500-watt PSU, because it was a great deal at Newegg and having a new case with USB 3.0 connections and other benefits sounded like a good idea, especially since this case/PSU combo was cheaper than most 500-watt power supplies by themselves. (No, it isn’t cheap or chintzy. It’s Rosewill, a good and reliable budget brand. My old case/PSU was also Rosewill, and it lasted over 7 and a half years.)
This makes me wonder if my old CPU and motherboard are actually perfectly healthy and could be revived into a low-powered budget computer. I have no need for that, nor anywhere to put it nor anything to do with it, but I won’t throw them away just yet.
A final note: the brass motherboard standoffs that come with any new motherboard are really necessary! Don’t forget them! When I put my new motherboard into my new case, I forgot about them, and the CPU and motherboard couldn’t even get any power. I was distraught and panicky, until I noticed that I hadn’t used these little cylindrical brass things that came in a small baggy and the motherboard wasn’t really screwed into the case in a way that seemed normal and correct to me. When I applied the brass standoffs correctly, everything worked great and I haven’t had a single hardware problem since. I don’t know how the case/PSU/mobo knows not to supply electricity to a mobo that is directly contacting the case, but it’s a good thing it does!