SATA > 6-pin adapter. Where to plug in?

[RadiatingLight]

So I'm trying to upgrade my old prebuilt PC (i7 2600, GTX 650) with my old GTX 770. the PSU is 450W continuous, so it shouldn't be a problem, but it only has 2 6-pin connectors, and no molex. stupid, right?

 

my GTX 770 needs a 8-pin and a 6-pin, and I purchased a SATA > Molex adapter to use with my Molex > 6-pin adapter, so it can fit.

I know this will deliver nowhere near the 75W a 6-pin is designed to deliver, and I know it's not ideal. please don't try to dissuade me from doing this.

 

I want to know if the adapted 6-pin should go into the 8-pin adapter. so (genuine 6-pin + fake 6-pin) to make 8-pin + (genuine 6-pin) OR (genuine 6-pin + genuine 6-pin) to make 8-pin + (fake 6-pin)

this probably doesn't make sense, so feel free to ask me to clarify.

[Electronics Wizardy]

Just get a 6pin to 8 pin adapter.

 

http://www.ebay.com/itm/JacobsParts-PCI-Express-Power-Splitter-Cable-6-pin-to-2x-6-2-pin-6-pin-8-pin-18/262928134914?_trksid=p2045573.c100505.m3226&_trkparms=aid%3D555014%26algo%3DPL.DEFAULT%26ao%3D1%26asc%3D41375%26meid%3D61ff8a53a1d64898ac1bde6ab0112431%26pid%3D100505%26rk%3D1%26rkt%3D1%26

[RadiatingLight]

1 minute ago, Electronics Wizardy said:

Just get a 6pin to 8 pin adapter.

 

http://www.ebay.com/itm/JacobsParts-PCI-Express-Power-Splitter-Cable-6-pin-to-2x-6-2-pin-6-pin-8-pin-18/262928134914?_trksid=p2045573.c100505.m3226&_trkparms=aid%3D555014%26algo%3DPL.DEFAULT%26ao%3D1%26asc%3D41375%26meid%3D61ff8a53a1d64898ac1bde6ab0112431%26pid%3D100505%26rk%3D1%26rkt%3D1%26

HAHAHA

That's literally the dumbest adapter I've ever seen.

 

Is there any way this would ever actually be useful?

[mariushm]

The sata connector has a theoretical max current of 1.5 A per contact, and there's 3 contacts for each voltage in the sata connector. So again, if the contact is perfect, you have 12v x 3 contacts x 1.5 A =  12 x 4.5w = 54 watts.

 

The cables going to the sata connector are AWG18 or AWG16 which can carry a lot of current, but the maximum recommended current is 16A for AWG18 and 22A for AWG16.  So basically the cable won't be an issue, it can carry over 200 watts without any problems.

 

Both pci-e 6 pin connector and pci-e 8 pin connector use only 3 pairs of 12v wires to transfer current.  The metal contacts are rated for 5-6A of current each, so since you have 3 pairs of wires that carry 12v, both pci-e 6 pin and pci-e 8 pin can safely push  3 pairs x 6a max per pair x 12v =  ~220 watts into a video card.

The PCI-e standard limits the pci-e 6 pin to 75w in the sense that for a video card to be able to say it's pci-e compatible, it must not take more than 75w through a pci-e 6pin connector, and not more than 150w from a pci-e 8 pin connector. The extra 2 wires don't carry more power, they're there just to make it possible for the video card to detect the different connector and take more power.

The idea was to have power supplies that used thinner cables for pci-e 6 pin and fewer connectors (so they could be cheaper) and use thicker cables and use those two extra wires for other things, but those "other things" would have made power supplies more expensive so they gave up on the idea and made everything much simpler.

 

So anyways, you have a SATA to molex adapter. 

Like I said, the sata end can take in 4.5A at 12v = ~ 55w.  The molex end can handle up to 5A , or about 60w .. So far so good.

The molex to pci-e 6 pin connector will move the 60w it receives from the 12v wire in the molex connector to the three pairs of wires... you'll still have only 60 watts.

If you use a pci-e 6 pin to pci-e 8 pin, you'll still have only 60w to give to video card but you'll just tell the video card that it's ok to try and take more than 75w.

 

Basically you shouldn't  use sata to anything to power a card with a 8 pin connector unless you know for sure the video card will take less than around 60w trough the 8 pin pci-e connector. It should be fine with pci-e 6pin connectors but nothing else.

 

There are 2 x molex to PCI-e 6pin/8pin...  you have 2 molex connectors, each with max 5a per connector, so you have 12v x 2 connectors x 5A = 120 watts and that's more than pci-e 6 pin and almost as much as pci-e 8pin.  Few video cards will constantly take current from pci-e 8pin as close to 150w so you would be fine.

 

You could use  TWO  x  sata-molex adapters , so that you'd have 2 x 4.5a x 12v = ~ 110 watts. , then connect an adapter that converts 2 molex to pci-e to those 2 molex connectors you just created, and you'll have about 110 watts of safe power to give a video card. For short bursts it may do 150w but it wouldn't be safe.

 

My advice would actually be to search ebay or some stores for broken / faulty power supplies  and CUT the wires with the pci-e 6 pin or 8pin connectors  and simply splice the wires to your power supply (on the sata wires or whatever). Worst case, you can cut a sata connector, and connect the wires to 12v and ground of the sata connector - this way you're not limited by the contacts inside the sata connector, your only limitation would be the thickness of the wires going to the sata connector.

[RadiatingLight]

1 hour ago, mariushm said:

The sata connector has a theoretical max current of 1.5 A per contact, and there's 3 contacts for each voltage in the sata connector. So again, if the contact is perfect, you have 12v x 3 contacts x 1.5 A =  12 x 4.5w = 54 watts.

 

The cables going to the sata connector are AWG18 or AWG16 which can carry a lot of current, but the maximum recommended current is 16A for AWG18 and 22A for AWG16.  So basically the cable won't be an issue, it can carry over 200 watts without any problems.

 

Both pci-e 6 pin connector and pci-e 8 pin connector use only 3 pairs of 12v wires to transfer current.  The metal contacts are rated for 5-6A of current each, so since you have 3 pairs of wires that carry 12v, both pci-e 6 pin and pci-e 8 pin can safely push  3 pairs x 6a max per pair x 12v =  ~220 watts into a video card.

The PCI-e standard limits the pci-e 6 pin to 75w in the sense that for a video card to be able to say it's pci-e compatible, it must not take more than 75w through a pci-e 6pin connector, and not more than 150w from a pci-e 8 pin connector. The extra 2 wires don't carry more power, they're there just to make it possible for the video card to detect the different connector and take more power.

The idea was to have power supplies that used thinner cables for pci-e 6 pin and fewer connectors (so they could be cheaper) and use thicker cables and use those two extra wires for other things, but those "other things" would have made power supplies more expensive so they gave up on the idea and made everything much simpler.

 

So anyways, you have a SATA to molex adapter. 

Like I said, the sata end can take in 4.5A at 12v = ~ 55w.  The molex end can handle up to 5A , or about 60w .. So far so good.

The molex to pci-e 6 pin connector will move the 60w it receives from the 12v wire in the molex connector to the three pairs of wires... you'll still have only 60 watts.

If you use a pci-e 6 pin to pci-e 8 pin, you'll still have only 60w to give to video card but you'll just tell the video card that it's ok to try and take more than 75w.

 

Basically you shouldn't  use sata to anything to power a card with a 8 pin connector unless you know for sure the video card will take less than around 60w trough the 8 pin pci-e connector. It should be fine with pci-e 6pin connectors but nothing else.

 

There are 2 x molex to PCI-e 6pin/8pin...  you have 2 molex connectors, each with max 5a per connector, so you have 12v x 2 connectors x 5A = 120 watts and that's more than pci-e 6 pin and almost as much as pci-e 8pin.  Few video cards will constantly take current from pci-e 8pin as close to 150w so you would be fine.

 

You could use  TWO  x  sata-molex adapters , so that you'd have 2 x 4.5a x 12v = ~ 110 watts. , then connect an adapter that converts 2 molex to pci-e to those 2 molex connectors you just created, and you'll have about 110 watts of safe power to give a video card. For short bursts it may do 150w but it wouldn't be safe.

 

My advice would actually be to search ebay or some stores for broken / faulty power supplies  and CUT the wires with the pci-e 6 pin or 8pin connectors  and simply splice the wires to your power supply (on the sata wires or whatever). Worst case, you can cut a sata connector, and connect the wires to 12v and ground of the sata connector - this way you're not limited by the contacts inside the sata connector, your only limitation would be the thickness of the wires going to the sata connector.

Thanks so much for your in-depth explanation. you're a hero.

I put in the GPU, connecting the adapted 6-pin, along with a real 6-pin from my PSU into an 8-pin adapter, and then plugged that into my GPU. so basically, the 8-pin can deliver a theoretical max of 130W instead of the 150W it's supposed to, and the other 6-pin on my card delivers the full 75W. I tested this with furmark for about 15 minutes, and although temps got to 84c, it ran like a champ. so it didn't draw more than 130W through the 8-pin, which I sorta expected, since I won't be overclocking.

[mariushm]

GTX 770 is a maximum 180w card. In most games won't use more than 150-160w.

A part of that will be taken from pci-e slot, up to around 60-65w (12v x ~5A limited by pci-e standard)

How much depends on particular implementation you have, some use 20-30w, some may get close to 50-60w

 

The card could have used a single pci-e 8pin but when overclocking you could go over 150w, hence why the extra 6-pin connector.

 

tagging to get notification : @RadiatingLight ...

 

[RadiatingLight]

Just now, mariushm said:

GTX 770 is a maximum 180w card. In most games won't use more than 150-160w.

A part of that will be taken from pci-e slot, up to around 60-65w (12v x ~5A limited by pci-e standard)

How much depends on particular implementation you have, some use 20-30w, some may get close to 50-60w

 

The card could have used a single pci-e 8pin but when overclocking you could go over 150w, hence why the extra 6-pin connector.

 

tagging to get notification : @RadiatingLight ...

 

Thanks again for all your help.

[Electronics Wizardy]

1 hour ago, RadiatingLight said:

HAHAHA

That's literally the dumbest adapter I've ever seen.

 

Is there any way this would ever actually be useful?

well it would work just fine. Those connectors can handle much more current that there rated for. A 6pin is rated for about 15 amps max, so they can do much more than that normal 75 watt rated max, and easily power a 770

 

[RadiatingLight]

27 minutes ago, Electronics Wizardy said:

well it would work just fine. Those connectors can handle much more current that there rated for. A 6pin is rated for about 15 amps max, so they can do much more than that normal 75 watt rated max, and easily power a 770

 

well it's rated for 75W. could probably deliver more, but I highly a 6-pin can deliver 300W

[Electronics Wizardy]

3 minutes ago, RadiatingLight said:

well it's rated for 75W. could probably deliver more, but I highly a 6-pin can deliver 300W

at 15 amps(rating from molex, the company that made the connector) it can do 160w in a 6 pin config. Its also rated for 250v, so you can do much more power than the 75 w from the atx standard.

[mariushm]

Series is MiniFit Jr. from Molex and is rated for 9A per contact (or wire pair) .. Limitation is from terminals resistance and max. gauge of wire (series is designed for AWG 18 or AWG16 but accepts as thin as AWG24)

With AWG18 cables very safe currents would be around 8A.

 

Series page: http://www.molex.com/molex/products/family?key=minifit_jr&channel=products&chanName=family&pageTitle=Introduction

 

Terminals page/datasheets :http://www.molex.com/molex/products/datasheet.jsp?part=active/0039000038_CRIMP_TERMINALS.xml#documentsAnchor

 

re contact resistance .. terminals have ~0.01 ohm resistance .. V = I x R ... V= 9A x 0.01A = 0.09v drop on the contact , P=I²xR=81x0.01 = ~0.8 w of heat produced where connectors mate, at each contact.

another reason why they used 3 pairs of wires even for 75w , reduce voltage drop and currents and spread heat across wider surface and also have some redundancy.