If it's a memory issue, it's almost always QPI/VTT (which is the supply voltage for the L3 and IMC) or VDIMM. QPI PLL and IOH are closely related because QPI is how the CPU communicates with the IOH; shouldn't have much to do with memory though and being closely related doesn't imply they need be the same or that they scale the same way...just that a high QPI clock can require adjusting both because of how the IOH is connected. Edit: It's worth mentioning that many PLL voltages don't need to be brute forced as too much voltage can introduce considerable noise.
Anyway, you can stress the IOH with anything that sends a lot of traffic between the CPU/memory and the rest of the system, as the only path from the CPU to SB or any of the PCI-E lanes is through the IOH.
GPU heavy benchmark tests that frequently change scenes/load new assets work well, as does stressing the southbridge. I'd recommend looping Unigine (Valley or Superpossition) or the Final Fantasy IV Stormblood (making sure the frame rate is uncapped in settings) benchmarks while simultaneously running random read benchmarks on some of your drives. If your NIC is attached to the IOH PCI-E lanes, you could run a network test at the same time.
...rightful liberty is unobstructed action according to our will within limits drawn around us by the equal rights of others. I do not add 'within the limits of the law,' because law is often but the tyrant's will, and always so when it violates the right of an individual. -- Thomas Jefferson
Last edited by Blameless; 04-01-2019 at 09:08 AM.