BCLK OC makes GPU OC unstable

jimbaw

jimbaw

jimbaw

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hi guys, i've got a fx8350 on a gigabyte 990fx ud5 currently at 4.5ghz on stock voltages and have been experimenting with overclocking with the bclk.
my last stable oc is with a bclk of 225 and multiplier on stock (20).

however, I when i try to lower my multi and raise my bclk to 250, i can get it stable but now my gpu oc is unstable and i can't go through a full benchmark on 3dmark11 and i get a lot of artifacts as well. my gpu goes all the way up to 75 (which i know is still within the limit) but with the other method, it stays well under 70.
anyways I know that the bclk affects pcie lanes so should i keep my current cpu oc or should i go for the other one and find a lower stable oc for my gpu?

just so you know, i've got zotac gtx 780 amp with a flashed bios and voltages don't go above 1.187 for 1250Mhz core and 6820Mhz mem.

sorry if it's a bit confusing
 
all you can do is lower the cpu oc till your gpu is stable

adding more cpu voltage might regain stability if your pushing the bclk more
 
Thing is the gpu oc is stable. Played 5 hours of skyrim and did a few runs on 3d mark last night and it was fine.

It's only if I try to add more bclk, even with a lower multi and clock. I'll just keep my oc for now and try to tinker with it once I go underwater. But can a higher bclk damage my pcie or sata devices?
 
Ok cheers I'll give it another go later. I'm just annoyed that I can't seem to go higher than 225 on the bclk when some people have 260 for their 24/7 oc.
 
it can be the limit of the board/bios or cpu

don't know much about amd systems but on intel its the same,you can only push so far

tested to see if its not the memory freq voltage that's limiting your bclk? as mem freq increases also,cpu northbridge voltage might help
 
You should have the option to lock the pcie frequency on that board?

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Yes I don't think it's the mem voltage because I've got it on 1.62 at the moment. I'm going to have a nap as I'm sleep deprived (teething baby) and can't think straight. I'll give it another go later. Cheers for your time though I appreciate
 
not sure if you can set/lock the pcie speed if its linked to the cpu bclk

on my old x58 board you could but newer intels are linked to the cpu,might be same for amd
 
I'll have a look if I can find such a feature as I've got a different bios (latest uefi beta. Think it's the FCb)
 
As far as i am aware, the PCIe speed is not locked when you change the fsb on an fx chip.

What happens when it goes unstable?

Do you get crashes and such or artifacts?

Could be CPU is becoming unstable it and due to heat from the clocked GPU as well as the CPU, as these fx chips are much easier to keep stable at cooler temps.
 
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