Question Cannot boot PC if PCIE 6-Pin is plugged in (and now, also out)

[Blind_Faith]

I thought my PSU was at fault, but after buying a new PSU, the same fault is happening.

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Using my old PSU:
Radeon HD7850 without 6-pin PSU power = PC not beeping, turning on and off repeatedly, no monitor output. I don't think the Radeon HD7850 (2GB) can work when the 6-pin PSU is not plugged in?

The above card with 6-pin PSU power = worked once, then didn't work, did the above - PC not beeping, turning on and off repeatedly, no monitor output.

nVidia 7800GT with 6-pin = the PC shuts off almost straight away without booting, no monitor output.

nVidia 7800GT without 6-pin = Worked fine. Maybe it was a fluke because this combination does not work on a new PSU.

Cheap graphics card (HD5450) that has no 6-pin requirement = worked.

No graphics card in at all = works.

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Using a new PSU:
nVidia 7800GT with and without 6-pin = PC doesn't boot, or beep, it shuts off in less than 20 seconds.

The cheap HD5450 wasn't tested on the new PSU because I already knew the 7800GT didn't work with or without the 6-pin.

No graphics card in at all = works.

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Perhaps the newer PSU has better safety features and isn't letting the PC boot with the 7800GT plugged into the PCIE slot? On the old PSU, that combination did work - what didn't work was if I plugged the 6-pin into the 7800GT. This is why I replaced the PSU, but the same thing is still happening.

Since the 7800GT worked fine in the PCIE slot - but only on the old PSU - I thought that ruled out the PCIE slot on the motherboard being at fault. Now with a new PSU, the PC won't boot with either the Radeon HD7850 (+6-pin) or the old nVidia 7800GT (+6 pin or without it).

Just before I got the fault, I was hammering my system playing Mirrors Edge 2 and the new Hitman on it, both games pushed it to the max, especially Mirrors Edge 2 that played fine for a while, then after a week or whatever I could never get it to run smooth, whereas before that it did run smooth, so it seems that it suddenly not running as smooth was a sign that something was on it's way out.

All I can think this is now, is the PCIE slot on the motherboard, but for some reason with my old PSU it boots with the 7800GT in and no 6-pin, whereas on a new PSU that combination won't boot.

Is this at a point now where it can only be a faulty PCIE slot on the motherboard?

 

[rgd1101]

full system spec? include make and model of the psu

 

[Blind_Faith]

MOBO: Gigabyte GA-H61MA-D2V

CPU: i5-2400 @ 3.10GHz

RAM: 12GB (8GB, 4GB) DDR3
(8GB - Team Group Team-Elite-1333)
(4GB - Corsair Vengeance LP CML4GX3M1A1600C9)

PSU: Thermaltake Purepower RX 600W

GFX: XFX Radeon 7850 (2GB)

Thats the old PSU, using it right now. The new one I tried was:
be quiet! Pure Power 11 600W CM

On the above new PSU, the system wouldn't boot with the nVidia 7800GT without the 6-pin in, but it does boot with that card without the 6-pin on the Thermaltake PSU.

I'm just going to swap this Gigabyte motherboard out for something like a used Asus B75M Plus. The Gigabyte always was a dirt cheap component! It's not a surprise that it's finally going on me after about 7 years of almost 24/7 use.

When I first got the fault and it not booting, it was after a restart. What if I had just never rebooted my system lol, I have a feeling it would still be working even now, about 4 months later. Hard to not reboot for 4 months, although I am sure I have had periods where I have managed it.

The PSU I am using has been on almost continuously for 14 years!

 

[Blind_Faith]

I just replaced the motherboard and the system will still not boot (or that is, it's not outputting anything to the monitor) with either graphics card plugged into the PCIE slot:

- AMD Radeon 7850 2GB (my best/newer card, takes PCIE 6-pin)
- nVidia 7800-GT 512MB (old card, takes PCIE 6-pin)

Up to now I have tried:

- Swapping the PSU, because I thought it was the 6-pin PCIE cable at fault, this changed nothing and it wouldn't boot with either graphics card plugged in on the brand new PSU, so I returned it and got a full refund.

"Oh good" I thought, "It's the motherboard at fault, those are half the price of a PSU".

Nope...

- I went back to my old PSU (nothing wrong with it) and replaced the motherboard with a different brand, this changed nothing and the PC will not output anything to the monitor if a PCIE card is plugged in with a 6-pin plugged in from the PSU!

It's not the PSU and it's not the motherboard, so it must be the graphics card, right?

If only it was that simple...

I can plug in a cheap PCIE card that doesn't require a 6-pin plug at the back of it and that work fine on both PSU's and both motherboards. I took it back out because the GPU memory bandwidth is a joke (onboard graphics is double the speed of it).

I know my Radeon 7850 might have bit the dust... but not the 7800GT as well! I know for certain that 7800GT worked the last time I removed it - not now though.

I am on the verge of just replacing my entire system! What can it be?

I suppose the next thing to try is to get hold of the cheapest PCIE graphics card I can find that needs a 6-pin cable plugged in (that won't work without one) and see if it boots up with that in.

It's not my DVI cable, that's working right now and is plugged into the onboard graphics of the replacement motherboard.

I don't believe that 7800GT I have had for ages that's always worked fine, has just magically stopped working.

I am so annoyed lol

 

[rgd1101]

test with just the igpu? 1 stick of ram?

 

[Blind_Faith]

test with just the igpu? 1 stick of ram?

Yes I did that when I first tried to diagnose it. I have 2 sticks of RAM and tried every combination.

What I haven't tried is taking out my CPU (i5 2400) and trying my old G860, but I am probably just going to upgrade the whole system.

The next thing to try to salvage this system would be a replacement graphics card but if every card that gets plugged in is getting shorted or something like that is happening, it's pointless risking it.

When I have upgraded, I will probably take both the HD7850 and 7800GT graphics cards to a shop and see if they can test them both, just because it's bugging me what it could be. If both cards have died then it's likely either my PSU or motherboard is killing them.

What gets me is, my PC was running fine and it took a reboot to cause it. It's a 7+ year old system so it's not like I can't justify the upgrade