I plugged an 8-pin EPS (CPU) cable into the GPU's PCI-E port. Is it damaged?

Question

The r9 290x I wanted to use needs 16 pins, my PSU which I thought had 1 PCI-E 6 + 2, 1 PCI-E 6 and 1 PCI-E 8-pin setups, actually had a second 8-pin EPS cable.

I don't currently have something to test the GPU with (the motherboard and all are fine; I just removed the GPU and put in an old GTX 770). So given this information, does anyone have any idea whether I can expect to have a fried GPU? No pop or smell appeared when I attempted it, which was nice!

Here is a picture of the pins.

Solution

Really this should not have been possible as the PCIe 8-pin connector was designed to have a completely different arrangement of pin shapes than the existing EPS12V connector. These are shown in the image below (notice the difference in bevelling on the corners):

^{(Image from here)}

It appears from the picture you posted that the cable that when you pushed it in, the corners of the square pins got scraped away allowing insertion - the moral is don't force connectors in (I'm not trying to be condescending, but it's worth keeping in mind).

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In this situation you have probably been saved by virtue of the card in question having both a PCIe 6-pin and a PCIe 8-pin connector. By having had both the 6-pin connector plugged in at the same time as the EPS12V connector, from the diagram above it is clear that basically all the 12V's and all the GND's are shorted together. While not a very good thing at all, it means that the PSU will not have been able to turn on, nor apply any voltage on the 12V lines.

Essentially this means your graphics card will never have seen any damaging voltages from having the polarity reversed on one of its connectors. So in theory the card should be absolutely fine.

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For reference, if the card has just an 8-pin connector, then if you powered it with an EPS12V, it would have been exposed to -12V which would have almost certainly have caused it to fry - and would probably also have taken the motherboard out along with it!

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As a side note, it would actually be possible to easily plug an 6+2-pin PCIe connector (these are the ones that can be separated or combined to be either 6 or 8 pin) into an EPS12V socket - in fact I did this once, but fortunately realised before turning it on. The true 8-Pin connectors (the ones which cannot be split off to go into a 6-pin connector) have a flat bar which joins across two of the pins to prevent doing this.

Comments

[Tom Carpenter]

I wasn't aware that it is possible to do that - by design the EPS12V cable has a different arrangement of notches to a PCIE 8Pin cable which should prevent insertion.

[chiloutus]

It seemed to fit, I'll admit it didn't fit as easily as the PIC-E 6+2 which just dropped it, but it fit. Hopefully it works when I get a chance to test

[Tom Carpenter]

I presume you powered it on. Did the PSU just shut down immediately or keep going? Also could you post a picture of the end of the EPS cable, I'm quite curious to see how it could have gone in the socket.

[chiloutus]

The PSU didn't seem to power on, no fans or anything like that spun up. Also I will upload a picture now

[Tom Carpenter]

It seems as you pushed the connector in, it stripped the corners of the square pins (not very good plastic!). If the PSU didn't power on, it means it was clever enough to detect that you had basically shorted 12V to GND and not turn on (the 12V on the EPS connector would short out with the GND on the PCIe 6-pin connector and vice versa). The card is probably fine as it will never have seen any voltage.

[chiloutus]

Pretty concise, okay I will see what I can do tomorrow about getting somewhere to test the card and update. Thanks!

[chiloutus]

Just an update to this for anyone who is in the same boat, card was fine! I got very lucky here.

[rayzinnz]

I just did your last sentence, plugged the PCIe into the EPS12V - fits nicely - turn on computer, big sparks and burning smell - plastic around the cable melted. It's odd there are no fuses in motherboard to prevent this. Anyway, motherboard, CPU, all components fine. They make 'em tough I guess.

[Tom Carpenter]

@rayzinnz If its a cheap power supply without proper protection, that can happen - the motherboard has some protection by virtue of the +2 bit of the 6+2 connector both being ground, so 12V is shorted to ground right at the connector rather than through the motherboard. It won't experience a damaging negative voltage, but without proper protection in the PSU you can easily melt the cables.

[lyrica]

@rayzinnz I have no idea why the 6+2 pin cables remove one of the squares on the +2 part, which would have prevented this from happening, short of ramming it into the socket. Instead, with 6+2 connectors, the +2 pins are both non-square, allowing them to be plugged into anywhere. Boggles my mind why they do this.

[apadana]

Could you also give your opinion about the similar case described here: electronics.stackexchange.com/questions/568192/…?