i7-5960X shuts off during boot when overclocking cache only when Linux + ACPI = ON

[helpme]

I have a weird issue with a PC using a i7-5960X and overclocking the cache.

Motherboard: Asus X99 Sabertooth TUF

Settings:
BCLK 125 Mhz
Mult: 37
Cache Mult: 28
Memory DDR4-3000

Vcore: 1.3v (manual)
Vcache: 1.2v (manual)
VSSCA: 1.05v (manual)
VCCin: 1.92v

Other peripherals:
Intel 750
Some cheap nvidia card

Power supply: Corsair AX760

Cooler: Corsair H110i

Temps: < 70C under stress test

Everything works find under windows 10 (Intel XTU stress test) and Linux (Ubuntu 14.04LTS, stress NG).

For my specific application (FPGA builds with Xilinx's Vivado) overclocking the cache actually does provide noticeable benefits. For example, going from 3Ghz to 3.5 Ghz cache results in a 10% reduction in build time. For a build that takes 1-2 hours, this is a large benefit.

However, I have an issue with Linux. When I try to overclock the cache to 4Ghz or 4.5 Ghz (Vcache 1.2 to 1.3V), I have no issues booting into windows and running XTU. However, in Linux, the system starts to boot and then shuts itself off.

If I disable ACPI via a grub boot option everything is fine... However, this results in USB not working (which is not a big deal since this machine is accessed remotely), but hyperthreading also does not work.

Any ideas why this might occur only under linux? It seems like an OS function since it only occurs when ACPI is ON. I've looked at the log files, but was not able to identify anything obvious.

 

[Burpo]

Have you tried standard bclk of 100? Maybe something like this..
BCLK 100 Mhz
Mult: 45
Cache Mult: 36
Memory DDR4-3000

 

[helpme]

I've experimented with a BCLK of 100 as well, but for some reason the system doesn't always boot when you try to use the memory at DDR4-3000. It's reliable with a BCLK of 125 at that memory speed.

I have tried to use a BCLK of 100 with DDR4-2133 to try experiment that way:

Mult 46
Cache 40-45
Memory DDR4-2133

The system still behaves the same way (windows/Linux with ACPI off is OK, but Linux with ACPI ON auto shuts off when running the cache between 40-45x).

Maybe I should just run with ACPI off and give up hyper threading?

 

[Burpo]

I think you may need to increase dram voltage a bit. Try VCCSA at 1.2v.

 

[zir_blazer]

Is possible that the reason why it doesn't works is because Linux may be putting more stress on the Cache that W10 does. Is the same thing as when your overclock is gaming stable but not stress test stable. Try with a lower overclock.
You may also want to confirm that there isn't a bug or something like that with Linux, ACPI and the Cache Frequency - try going for lower than default Cache Frequency and check if it works, in case that anything over 3 GHz gives you issues.

 

[.vodka]

My 2500k can do 10 passes of linpack at 6GB/8GB RAM, 4.5GHz 1.25v and feel completely stable on windows, yet if I try to boot Linux (Mint 64b)... it outright crashes. Linux requires 1.3-1.32v for getting to the desktop...

Having had that experience, I'd say you're missing a touch of voltage somewhere and linux is triggering instability... or do as zir_blazer says, back down your overclock a bit and see what happens.