Question Can't overclock both memory and CPU at once

Jun 26, 2020
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I'm a former Intel MB design engineer and have overclocked several other boards, so I feel like I’m not supposed to have to ask questions like this, but here’s what I’ve got.
-ASUS Rampage VI Extreme Encore
  • i9-10940x CPU (14 cores) two different CPUs
  • G.SKILL TridentZ RGB DDR4 4266 (F4-4266C17Q-32GTZR 17-18-18-36)
  • CORSAIR AXi Series AX1600i PS
  • Cooling: custom water loop

Both CPUs run stable at 5.0GHz but the temps peak at 90ᵒC running Cinebench 20, so 5GHz is no good for 24/7 use. To stay below 70ᵒC max, I'm running 101.3 * 47 = 4.76GHz all cores using adaptive mode with an offset of -.012V and AVX offsets at 3. I’ve also tested using static mode at this frequency. Both CPUs sit at 1.2V under heavy load using adaptive mode. Both CPUs can run Cinebench, Realbench, and XTU all day with these settings. At default CPU clock rates I can also run Cinebench all day at 3800MHz 15-15-15-36 without tweaking voltages.
The problem: When the CPU is overclocked as above, turning on XMP at 3800MHz 16-16-16-36 results in Cinebench throwing an error within a couple minutes. However, I can boot and run for 10-20 minutes at 3000MHz with the kit default 17-18-18-38. The latter indicates that the problem isn’t the clock speed or latencies. Tweaking VCCSA and VCCIO up or down doesn’t improve stability, nor does increasing the Core voltage.

I have re-flashed BIOS (latest 0603) and cleared CMOS with both CPUs with no effect.

Suggestions?
 

Ralston18

Titan
Moderator
What error is Cinebench throwing?

Power perhaps?

CORSAIR AXi Series AX1600i PS (PSU, 1600 watts- correct? Age, condition?)

I would think that 1600 watts would be more than enough. However, consider that the PSU may no longer be up to the task of supporting the desired overclocking. Failing in some manner or nearing design EOL.

What GPU is installed? How many drives?

Tally up the system's power requirements both manually and by using two or three online calculators.

Look for a consensus and use high end values if component wattages are provided as a range.

Compare the end wattage totals to the existing PSU. How much "extra" wattage is available?

Connect the PC to a Kill-a-Watt meter and monitor power usage as you tweak overclocking and run the system.
 

alexbirdie

Respectable
PSU seems OK, CPU seems OK, RAM seems OK -----> perhaps the motherboard does have any problems with providing the neccessary current, if CPU and Ram overclocked? VRMs and other components responsible for voltage and current supply on the mobo ?

Perhaps you can try another PSU? If OK then ----> old PSU buggy.

if NOK---> sorry to say, looks like a mobo-issue for me( although your motherboard is a very good highgrade one).

All neccessary additional power connectors connected on board ( there are 2 8-pin connectors and 1 6-pin)?
 
Last edited:
Jun 26, 2020
4
0
10
What error is Cinebench throwing?
Power perhaps?
First, thanks for your reply. :)

I don't recall the specific message, but it was a generic one about an error having occurred and stating the location where the things when wrong.
CORSAIR AXi Series AX1600i PS (PSU, 1600 watts- correct? Age, condition?)
I would think that 1600 watts would be more than enough. However, consider that the PSU may no longer be up to the task of supporting the desired overclocking. Failing in some manner or nearing design EOL.
What GPU is installed? How many drives?
The supply is about 6 weeks old, and is massive overkill for what I'm running so far. The Corsair iCue software allows me to track the supply voltage, power, current, etc., but not with much resolution. I can't 100% rule out brief supply transients, so I'll take another look at the voltages using an o-scope.

I just built the PC, so it also has only SSD drives.: two Samsung 970 EVO Plus 1T Drives in an iRST RAID 0 configuration, and a 360GB Intel Optane 905P. The graphics card is an MSI Vega 56 - not too terribly power hungry.
Tally up the system's power requirements both manually and by using two or three online calculators.
Look for a consensus and use high end values if component wattages are provided as a range.
Compare the end wattage totals to the existing PSU. How much "extra" wattage is available?
The supply is drawing 643W peak from the wall.

Thanks for the suggestions. With a new supply I handn't considered to look at the stability of the voltages.
 
Jun 26, 2020
4
0
10
PSU seems OK, CPU seems OK, RAM seems OK -----> perhaps the motherboard does have any problems with providing the neccessary current, if CPU and Ram overclocked? VRMs and other components responsible for voltage and current supply on the mobo ?

Perhaps you can try another PSU? If OK then ----> old PSU buggy.

if NOK---> sorry to say, looks like a mobo-issue for me( although your motherboard is a very good highgrade one).

All neccessary additional power connectors connected on board ( there are 2 8-pin connectors and 1 6-pin)?
I covered the PS in my previous post, but you pointed out another possibility I will address.
I've connected only the 24- and 8-pin headers, which is one manual option. Adding the 6-pin is a no-brainer I hadn't considered, however. Obviously something's not right, so this is a good idea. There is also a 4-pin Molex at the bottom of the board ASUS provides for dual GPU setups, but it certainly can't hurt to connect this header too.
 

alexbirdie

Respectable
I covered the PS in my previous post, but you pointed out another possibility I will address.
I've connected only the 24- and 8-pin headers, which is one manual option. Adding the 6-pin is a no-brainer I hadn't considered, however. Obviously something's not right, so this is a good idea. There is also a 4-pin Molex at the bottom of the board ASUS provides for dual GPU setups, but it certainly can't hurt to connect this header too.

Seems, that the Molex only provide more current to th PCIe-bus.

I am curious, if adding the 6-pin or even the second 8-pin-connection will solve the problem.
 
Jun 26, 2020
4
0
10
Seems, that the Molex only provide more current to th PCIe-bus.

I am curious, if adding the 6-pin or even the second 8-pin-connection will solve the problem.

I started with the 24-pin and 8-pin, then added the 6-pin - no difference. I should mention that my overclocking can result in the CPU drawing 500W and approaching , though the testing I'm performing now doesn't result in anywhere near that.

I've changed the CPU, and I'm currently testing with it. It appears to be better, but I haven't proved that the problem is completely solved.