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2x6 pin PCIE to 1x8 pin PCIE

Noughtboy

Noughtboy

Noughtboy

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Joined
18 Apr 2006
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Essex
I did post this originally under the PSU forum but there don't seem to be many takers nor is it as active as here. So, let me paste that message and see if you folk can help:

Hello all,

I currently have a Bequiet PurePower 530w model similar to this one http://www.bequiet.com/en/powersupply/43 except instead of 2x6+2 pin it is 2x6 pin. The specs are otherwise similar.

I was hoping to upgrade my AMD Radeon 5850 (2x 6 pin) to a Rx480 8GB AIB board (probably Sapphire Nitro+) but this requires an 8 pin plug.

I have seen 2x4 pin molex adaptors but don't think this is the way to go. The way I see it is I can only do this if I find an adaptor as in the heading (2x6 pin to 1 x 8 pin) but do they even exist? I think it is 2 male 6 pin to connect to the PSU and 1 male 8 pin to connect to the GPU. Perhaps the reverse. Will have to check.

On the very good assumption I do not wish to change the PSU, what are your suggestions? I may have to consider the GTX 1060 which isn't my first choice but certainly better then no upgrade.

530W is more than sufficient. My specs are i5 2500k, 1x5400 Samsung SATA 2 TB, 2x4GB DDR3, Radeon 5850 (currently), 3x92mm fans and 2x80mm fans with an SSD to be added and a couple of USB peripherals (dongle, KB and mouse)

Thanks

NB
 
Deleted[/QUOTE said:
I don't think that will cut it. The 6 pin supplies 75w and the 8 pin 150w. It would allow me to connect the GPU to PSU but only supply 75w +75w instead of the 150w +75w this GPU seems to require otherwise I should just get a reference RX480 or GTX 1060 both of which I am loath to do.

Isn't there a way to convert 2 PCIE 6 pin to 1 PCIE 8 pin?
Click to expand...
 
Last edited by a moderator:
RJC said:
I have replied to your thread in Power supplies which I have closed, as you have this one open.

Overclockers do this cable:
https://www.overclockers.co.uk/akasa-pci-e-to-pci-e-2.0-adapter-ak-cb052-cb-034-ak.html
Click to expand...

You have made the exact same suggestion as Flaw1ess , and as I said in reply to him:

"I don't think that will cut it. The 6 pin supplies 75w and the 8 pin 150w. It would allow me to connect the GPU to PSU but only supply 75w +75w instead of the 150w +75w this GPU seems to require otherwise I should just get a reference RX480 or GTX 1060 both of which I am loath to do.

Isn't there a way to convert 2 PCIE 6 pin to 1 PCIE 8 pin?"
 
Noughtboy said:
You have made the exact same suggestion as Flaw1ess , and as I said in reply to him:

"I don't think that will cut it. The 6 pin supplies 75w and the 8 pin 150w. It would allow me to connect the GPU to PSU but only supply 75w +75w instead of the 150w +75w this GPU seems to require otherwise I should just get a reference RX480 or GTX 1060 both of which I am loath to do.
Click to expand...

An 8 pin doesn't "supply" 150w... A GPU can pull 150w via an 8 pin connector, if it needs that much. A non reference RX480 may use slightly more than than the 75w 6-pin connector, but it is unlikely to be the full 150w.

Given that your PSU should supply enough wattage, and the cables are likely to cope with slightly more wattage, then I can't see a problem with that suggested cable (certainly a better option that a 2x Molex to 8 pin)
 
Armageus said:
An 8 pin doesn't "supply" 150w... A GPU can pull 150w via an 8 pin connector, if it needs that much. A non reference RX480 may use slightly more than than the 75w 6-pin connector, but it is unlikely to be the full 150w.

Given that your PSU should supply enough wattage, and the cables are likely to cope with slightly more wattage, then I can't see a problem with that suggested cable (certainly a better option that a 2x Molex to 8 pin)
Click to expand...

Look, I would be very happy with a £3 solution if that is all it takes. I am just a little hesitant that it is so easy.

Not looking to disparage your comment up above, but I thought AIB manufacturers installed 8 pins precisely because the 6 pin couldn't provide enough power.

My PSU is rated as 22A on each rail for a total of 44A and total combined power draw of 420W as per the Bequiet website

12V rails (multi-rail operation)2
12V single rail operation-
Overclocking key-
+3.3V (A)24
+5V (A)24
+12V1 (A)22
+12V2 (A)22
+12V3 (A)-
+12V4 (A)-
+12V5 (A)-
+12V6 (A)-
-12V (A)0.3
+5Vsb (A)2.5
Max. combined power 12V (W)420
Max. combined power 3.3V + 5V (W)130
Hold-up time (ms @ 100%)-

So, by assumption using your logic, divided by half I am getting 22A and 210 watts on each 6 pin which will then pass through the 8 pin. I am many years out of school but I don't think that is correct. I would love to be wrong, but I am sure that P=RI(2) or P=IV comes into play here or AIB would have no need to put in 8 pin PCIE connectors.
 
Noughtboy said:
Look, I would be very happy with a £3 solution if that is all it takes. I am just a little hesitant that it is so easy.

Not looking to disparage your comment up above, but I thought AIB manufacturers installed 8 pins precisely because the 6 pin couldn't provide enough power.

My PSU is rated as 22A on each rail for a total of 44A and total combined power draw of 420W as per the Bequiet website

12V rails (multi-rail operation)2
12V single rail operation-
Overclocking key-
+3.3V (A)24
+5V (A)24
+12V1 (A)22
+12V2 (A)22
+12V3 (A)-
+12V4 (A)-
+12V5 (A)-
+12V6 (A)-
-12V (A)0.3
+5Vsb (A)2.5
Max. combined power 12V (W)420
Max. combined power 3.3V + 5V (W)130
Hold-up time (ms @ 100%)-

So, by assumption using your logic, divided by half I am getting 22A and 210 watts on each 6 pin which will then pass through the 8 pin. I am many years out of school but I don't think that is correct. I would love to be wrong, but I am sure that P=RI(2) or P=IV comes into play here or AIB would have no need to put in 8 pin PCIE connectors.
Click to expand...

It will be fine. Stop thinking to much into it.
 
The 8 pin is only two extra neutrals and many PSU Manufacturers just do what the cable does linked above, just piggy backs off the other neutrals in the terminal.
 
The peak watts on one rail would be 12V x 22A = 264W, the other rail would then be limited to 420 - 264 = 156W.

Voltage is normally a constant, Amps or current draw varies and therefore wattage varies depending on the demand of the device.
 
Ok. Thanks RJC and Nkata. That is interesting.

But I suppose it begs the question, assuming my PSU is "standard", i.e. not a massive 1200w gaming jobby with 45A on each line but a "normal" PSU, why would AIB manufacturers need to move to an 8 pin connector with two more neutrals?

If the 6 pin could do the job, surely more people have access to 6 or 6+2 pin that 8 pin. And therefore, what is the use of an 8 pin connector if it doesn't really provide more power?

Regards

NB
 
The cable suggested above should work, but if you are not happy with that idea you can get the 2x6pin to 1x 8pin PCIe cable that you originally were after.

2x6pinto8pin.jpg


OCUK don't sell them though. :(
 
That cable (2x6pin to 1x8pin) was supplied with my EVGA 1070, 2 of them actually. It seems a perfectly acceptable solution.

Though I did just buy that 6 pin to 8 pin cable as a solution in my other PC.
 
I'm running a gtx1070 with a 6pin to 8pin pcie cable no problem.oh and it's in a HP desktop with a 450w psu :D
 
Noughtboy said:
But I suppose it begs the question, assuming my PSU is "standard", i.e. not a massive 1200w gaming jobby with 45A on each line but a "normal" PSU, why would AIB manufacturers need to move to an 8 pin connector with two more neutrals?
Click to expand...

The 6 pin spec only required 2x 12v lines, rather than the 3x 12v of the 8 pin. The 6 pin physical connector and cabling (18 gauge wire), can in theory cope with around 190W - but this assumes that the cabling of the PSU actually meets that spec (i.e. cheaper unbranded PSUs frequently skimp and use cheaper narrower gauge cabling), and also assumes a set temperature.

Limiting the "spec" to 75W increases the margin of safety, e.g. with poor quality PSUs and the hot environment of a PSU. Equally the 8 pin connector can in theory carry 288W, but the "spec" limits this to 150W.


Noughtboy said:
If the 6 pin could do the job, surely more people have access to 6 or 6+2 pin that 8 pin. And therefore, what is the use of an 8 pin connector if it doesn't really provide more power?
Click to expand...

The 8 pin spec has been available since 2008 - so access to 8 pin connectors doesn't really come into it. 6+2 is the same as an 8 pin connector - it just allows the flexibility to plug into either 6 or 8 pin.


sources:
https://en.wikipedia.org/wiki/PCI_Express#Power
http://www.tomshardware.co.uk/power-supply-specifications-atx-reference,review-32338-12.html
 
bru said:
The cable suggested above should work, but if you are not happy with that idea you can get the 2x6pin to 1x 8pin PCIe cable that you originally were after.

2x6pinto8pin.jpg


OCUK don't sell them though. :(
Click to expand...

i can't find these anywhere. i even tried aliexpress. where do you get these? i need them as i plan on using 2 x 4 pin molex to 6 pin adapter and a 2 x sata power cabled to 6 pin adapter. then use the 2 x 6 pin adapters from them to make an 8 pin adapter.
 
Psycho Sonny said:
i can't find these anywhere. i even tried aliexpress. where do you get these? i need them as i plan on using 2 x 4 pin molex to 6 pin adapter and a 2 x sata power cabled to 6 pin adapter. then use the 2 x 6 pin adapters from them to make an 8 pin adapter.
Click to expand...

Doesn't sound sketchy in the slightest :D
 
Armageus said:
Doesn't sound sketchy in the slightest :D
Click to expand...

why should it be? I mean the power draw will be split evenly over 4 cables. psu is a old 650W with only 1 x 8 pin and a 6 pin coming off the same lead. i need 2 x 8 pins. it's a semi modular power supply and i've lost all the modular cables. i don't want to change the 6 pin to 8 pin as 2 x 8 pins off the same rail could be dangerous no?


do any modular cables plug and play and standardised? or would i need the specific ones for that psu?

it's this PSU

XFX 650W XXX Hybrid Modular Power Supply

I might just stick this in my new rig and then stick my new PSU 450W with 2 x 8 pins in the old rig. However as you can see it's like 7 years old. but it's had very little use. if a decent PSU dies the chances of it killing hardware are pretty slim right?
 
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