Dell Optiplex 7040 crashing while GPU on load

[harmudharh]

Hi. I have a Dell Optiplex 7040 upgraded using a GTX 960. The power supply was not enough for the card so I bought a new 630W power supply. Everything else is the same.

The PC runs quite fine normally but when I run graphics intensive apps like games or even 3DMark for a while, it suddenly force shuts down and one second later all fans go on max for a few seconds before going off. If I turn on the PC after this happens, all the fans again go on max for a few seconds and then everything turns back on normally. I cannot figure out the issue at all.

I am however quite sure that temps are not the problem. I keep monitoring temps to see when the system crashes. The hottest it gets is 65 degrees on CPU and 70 degrees on GPU, which are quite decent. I have even seen a shutdown when the GPU was only 56 degrees.

What can be the issue? Please help.
Here are the system specs.
Intel i7 6700 @ 3.4GHz
16 GB DDR4 RAM
EVGA GTX 960 2GB SSC
Raidmax 630W power supply

I am using an adapter for the power supply because the dell motherboard uses an 8 pin connector instead of normal 24 pin. This is the one:
https://www.amazon.ca/Optiplex-Power-Supply-Motherboard-Adapter/dp/B0759G52X6/ref=sr_1_1?s=electronics&ie=UTF8&qid=1513104747&sr=1-1&keywords=24+pin+dell+to+8+pin+adapter

 

[william p]

Check the rating of the 5V rail on the new PSU vs. the old. Some Dells continued to use that when the aftermarket went away from it. EVGA PSUs are pretty good about this. The GTX960 and the 75W GTX1050Ti are at the same level on the GPU Hierarchy chart. Maybe a new GPU instead of a PSU swap?

 

[william p]

I went to Johnnyguru forum and the thinking is Raidmax just badge engineers random PSUs. There's actually no way to knowing what PSU you actually have.
They say even the same part# can be from various suppliers. My guess is the PSU is the problem.

 

[harmudharh]

Thanks for replying. I think you might be right. There seems to be something wrong with power delivery.
Also I noticed there might be something with the 24 to 8 pin adapter. It only uses pin 8-11 and 16-18 from the 24 pin connector, which are +12V1 DC, +12V1 DC, +5VSB, PWR_OK, PS_ON#, COM, COM, COM. It uses none of the other +5VDC or +3.3VDC. Would that be enough to power everything?

 

[william p]

The 24 pin connector goes all the way back to Socket 478 Pentium 4 BTX computers, the 20 pin it's based on goes back to before socket 7. Voltage regulators don't care what Voltage is coming in. They regulate it. It's what they do. Dell decided to stop the antiquated nonsense of ATX compliant PSUs. Your choices are an adapter, or a Dell PSU that fits your computer.

 

[harmudharh]

I checked all the voltage rails. The Dell PSU used only 2 12V pins and one 5V stand by, no other 5V or 3.3V ones. The adapter also takes only those pins from the PSU. The GPU and CPU also use only 12V rails so the whole system is being powered by a single 12V rail in the PSU. I estimated the total wattage to be around 275W, and the wattage that the PSU is capable of supplying is 576W on the 12V rail alone. Why would the system still crash?

 

[harmudharh]

Another thing now, I tried bitcoin gold mining on the GPU. It runs perfectly normal even at 100% load. No crashes whatsoever. I could even overclock the GPU, gaining additional 87MHz clock. The system is stable.
This kinda throws away the reason to look into PSU as an issue.