HP Workstation Z800 fully shuts down when stopping CPUz stress test

[M_12301]

I bought a second hand HP Workstation Z800 which has 2 Xeon X5690 CPUs, and I installed Windows Server 2019 on it on a new HDD.

I detected an issue while testing out the workstation; when I run CPU-Z stress test, I can keep it running for minutes, but when I click the "Stop stress test" button, the workstation fully shuts down (No BSOD, no automatic restart, just shuts down).

I tried removing HDD I don't need, and also disabled RAID. I also updated the BIOS from 3.13 to 3.61, but nothing fixed the issue. I also removed the two Nvidia Tesla GPUs that were in there, and installed a ~45W AMD one, but didn't solve the issue.

The CPU temperatures don't go over 76C maximum during stress test.

I am starting to feel that it is a PSU issue, but why does it happen only when stopping the stress test and not during the stress test?

Also, can I use a normal ATX PSU from the market? Does it fit? Does it work out of the box? If not, is there a workaround to use a normal ATX PSU?

I don't want to buy the Z800 PSU because it costs hundreds of dollars for a "refurbished" which might have the same issue or even worse.

[DGroves]

the z8xx seres of workstations came with non ATX compatible power supplies  a 850 watt base and a 1250 watt upgraded unit which is the preferred unit and REQUIRED for dual cpu's or a single high wattage cpu

a used z800 1250 unit is around 150/200 dollars

the cpu coolers also came as base low power two heatpipes   or high power 3 or 4 heatpipes ones, you can use the z820/840 cpu coolers

some time back you could buy adapters off Alibaba/ebay to convert the non std HP power supply into a ATX one but thes are most likely bo longer available...............................i stand corrected here's a link

https://www.ebay.com/itm/186181760619?chn=ps&srsltid=AfmBOoqk7ETpASDYrVAScie_Jbc6CHAU0nsCjm8jxiaDxnJ...

personally i would upgrade to a z820/840 unit or a lenovo p520 (check prices on ebay)

last, i would try a linux live CD/DVD and run a stress test and if it does not have any shutdown issues  then suspect the cpuz app as the root cause

[M_12301]

I found this machine in a local second hand market, and they are not much available in my country, so buying a different model or selling mine is hard, and ebay shipping fees would be really high because of the weight.

My only choices are to either fix the current PSU by hand, or switch to an ATX PSU, and also move the motherboard to a normal EATX case if I can get it to fit.

But those choices are only if I conclude that the issue is related to the PSU.

[M_12301]

OK I have solved the issue.

I disabled the Intel Turbo feature from the BIOS and now stress testing doesn't cause any issues.

It seems this CPU (Intel Xeon X5690) is not fully supported by the Z800 as far as I have read in the manual (Not in the list), and I also noticed that during stress testing, the CPU power would become ~143W, which is 13W above the CPU TDP (130W). So the Turbo feature might have been poorly overvolting the CPU.

I also didn't see any benchmark loss after disabling Turbo.

I don't think the issue is PSU related, because I already disconnected many components which use high power (GPUs, HDD) but this didn't solve the issue earlier.

[DGroves]

the z800 does/did support the 5690 and the older 55xx series on the later rev 2 motherboards

(the orig board rev only supports 55xx series)

you need one of the later/latest HP "quickspecs" (which has several revisions) which will show the 5690

see attached pdf

HP High Performance Active Fan Heatsink

Z800 part# 463991-001 or 535588-001

[M_12301]

Well when enabling Turbo I do not get any benchmark benefits, the only thing I get is increased power consumption and heat (reaches above 70C compared to 60C) and instability.

The benchmark score is the same whether Turbo is enabled or disabled.