CPU upgrade -> RAM issues

castiman · June 24, 2020

Hello,

I just upgraded from an AMD Athlon II X3 455 to a FX-6300. The mobo is an Asus M5A78L-M LX with 2 Kingston (2x4GB) DDR3 1333mhz. The RAMs (together) work fine with Athlon instead with the FX, after different tries, I've noticed that work (only one) without issues only if I leave the first slot (DIMM_A1) empty.

I've already tried to test the same stick worked on DIMM_B1 on DIMM_A1 but nothing, the system pass the POST but crash when start to load any system (I've also tried to load directly from USB Memtest86).

I thought I might have "broken" the slot (although when I changed the CPU I didn't touch the RAMs) and so I tried the Athlon again and everything worked as before. (I've always reset the BIOS with the jumper on the mobo after every swap.)

The FX-6300 has been purchased used, but since it only works with one slot I doubt it could be the problem, maybe I have to make some settings in the BIOS or is it a limitation of the motherboard? (although it is present in the list of supported CPU)

I can't find anything online about this issue and I have never ran into it, I've tried to contact the Asus tech support, but I'm waiting an answer. Any ideas?

Thanks in advance!

Windows7ge · June 25, 2020

1333MHz is a very safe speed to be using on FX and if it works with one stick I'd have to lean towards a hardware problem not a compatibility problem. Since everything works with the old CPU but not the new one it sounds like the new FX CPU has some internal problem with it with that memory channel. Perhaps the channel is "dead". Ether way you'd need a new CPU.

castiman · June 25, 2020

19 hours ago, Windows7ge said:

1333MHz is a very safe speed to be using on FX and if it works with one stick I'd have to lean towards a hardware problem not a compatibility problem. Since everything works with the old CPU but not the new one it sounds like the new FX CPU has some internal problem with it with that memory channel. Perhaps the channel is "dead". Ether way you'd need a new CPU.

Thank you for your diagnosis!

I firstly thought about an issue on CPU but working with only one stick I've reconsidered.

Unfortunately I don't have another motherboard to try the CPU, I will try to ask for a refund but I think it will be difficult to get it (Asus support answered me in the same way, i.e. they think more about a CPU problem).
If I can also get a partial refund, I'm thinking of buying 8gb RAM at 1600MHz, is that a good idea?

(I'm starting to think I made a mistake with this upgrade ).

Windows7ge · June 25, 2020

18 minutes ago, castiman said:

Thank you for your diagnosis!

I firstly thought about an issue on CPU but working with only one stick I've reconsidered.

Unfortunately I don't have another motherboard to try the CPU, I will try to ask for a refund but I think it will be difficult to get it (Asus support answered me in the same way, i.e. they think more about a CPU problem).
If I can also get a partial refund, I'm thinking of buying 8gb RAM at 1600MHz, is that a good idea?

(I'm starting to think I made a mistake with this upgrade ).

The thing is if everything works with the old CPU but a memory channel stops working when a new one is installed then the CPU itself is the most likely culprit. Motherboard could be the culprit but it's less likely, and a ram compatibility/error issue is the least likely here.

RAM is one of those things where more only equals more performance up to a point. If you have a use for 16GB you can buy 16GB. 1600MHz is still a safe speed. Things start getting iffy around 1866MHz+.