GPU needs 2x8pin but i only have 1 8pin and 1 6pin

[yeehaw]

So i'am doing a school project where i'm putting together pc's to play some games, í have to use whatever components i can find around the storages and what not and i found a HD6970 that is the best that my school has and i really want to use it since theres nothing quite like it to find.

 

The problem is that the shitty psu's that are available only have 1 8pin and 1 6pin and the card needs 2x8pin and it wont boot with one psu, i plugged in another 8pin from a separate pc and it booted so it's definetly the 6pin thats causing issues, is there a way i could "fool" the gpu into thinking it has 2x8pin or is this a lost cause?

[jaslion]

You need 2x8pin the hd 6970 requires it to boot simple as that.

[SignatureSigner]

https://www.amazon.com/Cable-Matters-2-Pack-6-Pin-Adapter/dp/B01DV1Z32Y

never tried one of these but it could work :?

[NelizMastr]

7 minutes ago, yeehaw said:

So i'am doing a school project where i'm putting together pc's to play some games, í have to use whatever components i can find around the storages and what not and i found a HD6970 that is the best that my school has and i really want to use it since theres nothing quite like it to find.

 

The problem is that the shitty psu's that are available only have 1 8pin and 1 6pin and the card needs 2x8pin and it wont boot with one psu, i plugged in another 8pin from a separate pc and it booted so it's definetly the 6pin thats causing issues, is there a way i could "fool" the gpu into thinking it has 2x8pin or is this a lost cause?

If the rule is to use only parts that are available in storage, you'll have to also find another PSU that has 2 8-pins or 2 6+2 pins at least.

[Eigenvektor]

4 minutes ago, SignatureSigner said:

https://www.amazon.com/Cable-Matters-2-Pack-6-Pin-Adapter/dp/B01DV1Z32Y

never tried one of these but it could work :?

It should, but it also means you're potentially drawing more power from that 6-pin than it is rated for. A good power supply should be able to provide enough power, but you're still operating outside its specs. So ideally you'd get a better power supply that does have 2x 8-pin.

 

A 6-pin is rated for 75 watt, while an 8-pin is rated for 150w, so you'd be drawing up to double the rated power from the 6-pin, depending on how power hungry the GPU is.

[SignatureSigner]

 

2 minutes ago, NelizMastr said:

If the rule is to use only parts that are available in storage, you'll have to also find another PSU that has 2 8-pins or 2 6+2 pins at least.

Dual PSU? Could do what Austin Evens did in scrapyard wars.

[Eigenvektor]

3 minutes ago, SignatureSigner said:

Dual PSU? Could do what Austin Evens did in scrapyard wars.

I'm not an electrical engineer, but I think using two different power supplies for the same component could be trouble. If the voltage on their 12v rails is slightly different, you'll get a current flowing between them. Not sure how problematic this could be.

[SignatureSigner]

1 minute ago, Eigenvektor said:

I'm not an electrical engineer, but I think using two different power supplies for the same component could be trouble. If the voltage on their 12v rails is slightly different, you'll get a current flowing between them. Not sure how problematic this could be.

just an idea Austin evens did it

[NelizMastr]

2 minutes ago, SignatureSigner said:

just an idea Austin evens did it

Austin is not an electrical engineer though and it was only used briefly. So I wouldn't assume from a YouTuber they fully know what they're doing.

[SignatureSigner]

10 minutes ago, NelizMastr said:

Austin is not an electrical engineer though and it was only used briefly. So I wouldn't assume from a YouTuber they fully know what they're doing.

never said I did. If he just needs the system to work for a short time it might work in a pinch. If anything austin had NO idea what he was doing.

[mariushm]

You could just short the pins on the back of the connector with a bit of solder. 

The extra 2 pins are ground, same as all pins from one of the rows ... just use a multimeter to check continuity if it's not visible on the circuit board.

 

But at the end of the day, make sure the power supply can actually supply the current (the Amps) on the 12v outputs ... look on its label. 

That 6970 will consume up to around 200 watts ... so add another 100-150 watts for the CPU, motherboard, hard drives ... and you basically need a power supply with AT LEAST 350 watts ( 350w / 12v = 29A)  on the 12v rail(s). 

 

 

[kelvinhall05]

7 minutes ago, mariushm said:

You could just short the pins on the back of the connector with a bit of solder. 

The extra 2 pins are ground, same as all pins from one of the rows ... just use a multimeter to check continuity if it's not visible on the circuit board.

 

But at the end of the day, make sure the power supply can actually supply the current (the Amps) on the 12v outputs ... look on its label. 

That 6970 will consume up to around 200 watts ... so add another 100-150 watts for the CPU, motherboard, hard drives ... and you basically need a power supply with AT LEAST 350 watts ( 350w / 12v = 29A)  on the 12v rail(s). 

 

 

 

If that PSU does not have two 8-pin connectors I can 100% guarantee it does not have 8-pin current on the 6-pin connector. There would be no reason for the PSU manufacturer to limit that connector to a 6-pin if they have the power to run an 8-pin.

 

 

OP, upgrade the PSU, basically every suggestion in here that does not involve somehow giving it the power it needs is a fire hazard.

[mariushm]

10 minutes ago, kelvinhall05 said:

If that PSU does not have two 8-pin connectors I can 100% guarantee it does not have 8-pin current on the 6-pin connector. There would be no reason for the PSU manufacturer to limit that connector to a 6-pin if they have the power to run an 8-pin.

 

 

OP, upgrade the PSU, basically every suggestion in here that does not involve somehow giving it the power it needs is a fire hazard.

Probably 99.5% of the power supplies out there  DO NOT monitor the current on the cables and DO NOT have separate 12v outputs - basically all the 12v wires go to the power supply circuit board and get soldered in the same circuit, same thick trace on the circuit board. 

So the psu will have same amount of current on 8 pin as on 6 pin ... current will be equally split between the connectors. 

 

There were quite a few brand name power supplies that had a 8 pin and 6 pin connector as a way to artificially make their higher wattage models better. For example the 400w comes with only a 8 pin, the 420/450 comes with 8 + 6 and the 500-550 come with 2 x8 pin ... 

 

So your statement is not always true, that's why you have to check the label on the power supply and then you have to use your judgement and consider whether you trust the brand that they're not lying about the numbers, that they're not inflated. If the psu is from a brand name with decent reputation, it's a high probability the numbers are true. 

 

Also worth noting that the 6970 consumes only around 200-210 watts, so it doesn't really need 2 pci-e 8-pin connectors. It could have been made with 8+6 or even a single 8 pin (if you disable overclocking and tweak voltages to get card within maximum current of 8pin + slot power)

 

The card will take a bit of that 200-210 w from the pci-e slot, probably 30-50 watts, and the rest will be taken from extra pci-e connectors, or a bit over 150 watts.

 

The 8 pin connector is rated for 150 watts but the actual wires and pins in the connector are capable of more, around 100 watts per pin/wire is safe, it's just the pci-e standard organization that defined the limits at 75w and 150w.  - it's quite possible they could have tweaked the bios on the card to make the card behave and always draw less than 150 watts from the pci-e 8pin connector, and make the card with a single 8 pin connector... BUT ... it's a 6970 ... these were cards that advertised overclocking and all that... 

So they had to add a 2nd connector ... and most manufacturers will just add a 2nd 8 pin connector because  young gamers see 2 x 8 pin and think more power, more fps, better overclocking and card sells better ... and also the manufacturer only has to stock one part instead of two , and reduces confusion  ( " ugh, my power supply only has 8 pin connectors, it doesn't have 6 pin ones, can't buy this video card")