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Visionary Tools



Registered: 06/23/07
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Last seen: 1 year, 7 months
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PCI-E v2 power connectors
#22061953 - 08/08/15 09:19 AM (8 years, 5 months ago) |
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I went through a lot of hassle trying to find an eight pin connector. Found a shop ten miles away that had two in stock and got a 6pin to 8pin PCI-E to PCI-E v2 connector for £5 (plus about £2 for fuel getting there and back)
I looked into it. It has the same number of yellow wires that the six pin has, but two extra ground pins. Apparently PCI-E six pin is rated up to 75 watts, and PCI-E eight pin 150 watts, even though it's the same number of 12v cables.
In the past, when I had a geforce 7800 which was the last power hungry card I had, it used 2xPCI-E connectors. I do remember when I swapped it that where the power plug was soldered on to the PCB the solder was discoloured.
So, it's one of those things I have to ask about: Why does this exist? What advantages does it have over the existing six pin connector, what's wrong with using two connectors (which, by the way, two connectors merge into one socket on my power supply, so each of those sockets are rated up to 150W)
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Shroomism
Space Travellin



Registered: 02/13/00
Posts: 66,015
Loc: 9th Dimension
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Because 8pins allow for more power. Some cards require 1x 6pin. Some have 1x 6-pin, 1-8pin. Some of the most power hungry cards require 2x 8-pins. You can use 6pin adapters to make an 8-pin.. but the better long term solution would be getting a PSU that already has the requisite power connections, most modern PSUs have both 6 and 8-pin connectors. Many will have a 6-pin with an extra 2pins on the side that you can use it as either an 8 or a 6.
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Visionary Tools



Registered: 06/23/07
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Re: PCI-E v2 power connectors [Re: Shroomism]
#22062556 - 08/08/15 12:38 PM (8 years, 5 months ago) |
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Eh, I have an 8 year old seasonic m12, they don't make it anymore and it has 2 PCI-E sockets for a combined current draw of 25A. IT'd be feasible to power even the most power hungry using multiple PCI-E 6 pin connectors.
I really don't see the advantage to it. Same with SATA power connectors, even those flat SSD's could have room for molex, and I'm not sure if any SATA device uses the 3.3v rail.
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koraks
Registered: 06/02/03
Posts: 26,672
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Maybe it's to discourage people from running newer, more power hungry cards from older psu's that may or may not yield enough power. I'm really not sure, so just speculating.
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Visionary Tools



Registered: 06/23/07
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Re: PCI-E v2 power connectors [Re: koraks]
#22062983 - 08/08/15 02:45 PM (8 years, 5 months ago) |
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that's what I don't get. WE've had 1Kw+ power supplies for over 10 years now, mine's 750W, which personally I consider overkill but one of these days I may be grateful for it.
I'm saying physically it's dumb. If PCI-E demanded 4 12v rails and 4 return channels that'd be sensible. Then you could have 3.125A per channel, a step up of an amp compared to 75W for PCI-E.
I really can't find a clear reason for it and I find it utterly baffling.
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koraks
Registered: 06/02/03
Posts: 26,672
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Well I agree it's odd and especially that the 8 pin connector only adds ground wires.
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Shroomism
Space Travellin



Registered: 02/13/00
Posts: 66,015
Loc: 9th Dimension
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Quote:
Visionary Tools said: that's what I don't get. WE've had 1Kw+ power supplies for over 10 years now, mine's 750W, which personally I consider overkill but one of these days I may be grateful for it.
I'm saying physically it's dumb. If PCI-E demanded 4 12v rails and 4 return channels that'd be sensible. Then you could have 3.125A per channel, a step up of an amp compared to 75W for PCI-E.
I really can't find a clear reason for it and I find it utterly baffling.
Back in the GTX 480/580 days, when the 8-pin PCI-E connectors really started coming into play with super power hungry and powerful GPUs.. People were putting multiple 480s/580s/590s in like tri-quad SLI and it was pulling so much power under load that it was literally melting the 24-pin on the motherboard, because the cards were trying to pull so much power under heavy loads. Then mobo manufacturers started adding a supplementary 6-pin PCI-E power connector to their mobos to provide more consistent voltage across the PCI-E lanes under load, especially with multiple high end GPUs. The motherboards at that time (X58 v1) were not equipped to start handling multiples of such power hungry GPUs. In addition, cheap PSUs very soon met their maker and often took other components with them. The more modern Nvidia cards are much more power efficient but also powerful, but the highest end cards still want 8pins.
As for the differences: 6-pins provide: 2x 12V 2x Ground 1x Connector detection (connect to ground to tell card that connector is present) 1x Optional 12 V
8-pins provide: 3x 12V wires 3x Ground wires 2x connector detection wires
The 8-pin has an extra ground and an extra 12v in most cases and is designed to supply up to 150W of power, the 6-pin only 75W.
I'm not sure exactly what you are arguing about. It depends completely on the PSU and whether it's single rail vs multi-rail, and how many amps it can carry to the 12v rail. Almost all modern PSUs have 6+2 pin PCI-E power connectors, because virtually every high end card these days has an 8-pin, usually a 6-pin AND an 8-pin. Some really powerful cards have 2x 8-pins. If a card is capable of pulling 350-400watts under max load.. a couple 6pins will not cut it.
It's not dumb. I'm quite sure the PSU engineers had very good reasoning behind it. 1. for safety 2. for more stable voltage delivery and 3. for higher powered GPUs which were becoming increasingly more common.
1kw PSU literally means nothing in my experience. I remember once a guy was trying to hook up a 590 to a 1kw PSU, he couldn't get it to power on and we couldn't figure it out. Finally we looked at the specs of the PSU, and it was a Dell 1,000w PSU from like 2002, it had a bunch of 6-pin connectors so he could use adapters. But after looking at the specs of the PSU.. I saw that it had multiple 12v rails and only a COMBINED amperage of only 20a on the 12v rail.. not even close to sufficient for a single 590, despite it being a 1000w PSU. So it depends entirely on the PSU.
PSUs have become much more refined in the last 10 years. It depends entirely on the manufacturer of course.. but there are more higher quality modern PSUs than there used to be IMO.. more safety features, more stable voltage delivery overall becoming more common, 12v rails capable of putting out 60+ amps, etc.
Quote:
Visionary Tools said: Eh, I have an 8 year old seasonic m12, they don't make it anymore and it has 2 PCI-E sockets for a combined current draw of 25A. IT'd be feasible to power even the most power hungry using multiple PCI-E 6 pin connectors.
I really don't see the advantage to it. Same with SATA power connectors, even those flat SSD's could have room for molex, and I'm not sure if any SATA device uses the 3.3v rail.
I can think of many GPUs that PSU would not be capable of powering. Also remember to use a 6pin to 8pin adapter.. it requires TWO 6-pin PCI-E connectors to make ONE 8-pin. If you only have 2 6-pin PCI-E power connectors, you are SOL for a lot of cards.
The advantage to having the 8-pin is that if you have a card that requires it.. then you need it.
You can get by in some cases with using 2x 6-pin to 8-pin adapters.. IF your PSU has enough amperage on the +12v, AND has enough 6-pin PCI-E connectors... but that's no long term solution.. I used to work for a GPU manufacturer.. and I always told those people to just buy a new PSU, adapters are not ideal.
The reason for SATA power connections is multiple. Molex does not fit on 2.5" drives. It also allows for easier insertion of the connection. Not a big deal for desktops, but a huge deal for servers and notebooks. Some drives do use 3.3v. SATA is just a better connection. Trying to plug in those molex connectors was always a giant pain in the ass. Molex was supposed to die off. But it's persisted because a lot of fans and other peripherals still use them.
But yeah, I'm sure GPU manufacturers did part of it by design, to dissuade the multitude of idiots that would buy a $1000 power monster video card, or multiples of them.. and call us up and ask if they could use their $20 No name PSU from 2000 to power it. I can't tell you how many people fried components because they were using inferior PSUs for the hardware they were trying to power.
I will never understand why someone would buy the highest grade, most expensive video cards on the planet... and then want to get the cheapest no-name bargain bin PSU they can find to power it. These people exist. And then stuff like this happens

That's like upgrading your car, dropping a 700HP supercharged LS7 into your car, and putting in a stock fuel pump from a pinto and a transmission and drivetrain from a Yugo. Something is probably gonna break, or not work right.
Not saying this has anything to do with you. Just some of the thought process behind the 8pin probably. Many power hungry cards demand more power than 6pins can safely provide under max load.
Seasonic makes some of the best PSUs in the industry, but if yours is 8 years old and only has 2x 6-pin PCIe connectors, it might be time to start thinking about upgrading. I never recommend using PCI-E power adapters, your PSU should at default be capable of supporting everything in your system. My PSU is a ~3 year old 1200w Coolermaster Platinum, has 12 (TWELVE) 6+2 pin PCI-E connectors. Extreme overkill for my setup... but your PSU only pulls as much power as your system needs, so it's not like any goes to waste, and with the higher efficiency PSUs you get much better power efficiency.
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Visionary Tools



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Re: PCI-E v2 power connectors [Re: Shroomism]
#22077966 - 08/11/15 07:05 PM (8 years, 5 months ago) |
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Quote:
Shroomism said: Also remember to use a 6pin to 8pin adapter.. it requires TWO 6-pin PCI-E connectors to make ONE 8-pin. If you only have 2 6-pin PCI-E power connectors, you are SOL for a lot of cards.
A y-split 6pin to 8pin? May be sensible but the PSU has two six pin sockets. Both of those can have two six pin outputs, for a total of 4 6pins, 300W in total. It's rated up to 750W, and has a 40mm secondary fan on it that'll spin up if it gets really hot. It's a bronze rated unit, in the future I may for go for a platinum rated one. I've noticed the new modular seasonic PSU's even have a socket for the motherboard 24 pin connector.
Now, what you say about overloading cheapy PSU's and taking out a system with it, thus using a new connector so people can't do that sounds plausible, but I've always had paranoia about substandard PSU's, which is why I always go for seasonic, or failing that FSP. I'm sure there's other good PSU manufacturers out there, like I'm sure there's other reputable motherboard manufacturers besides Asus, but I'm irrational when it comes to electronics.
I've never gone with SLI/Crossfire, pretty much every single review I've seen has shown that the next model up outperforms two previous ones in SLI. When I had a 7800GTX I tried some benchmarks. Highest power draw I saw was around about 300W (think I had an FX55 back then, or a core 2 duo).
Maybe in the future I'll go with some crazy dual titan (or 4x titan because I have more money than sense) system with a silly priced intel i7 which would necessitate a 1kw power supply, but until then it's not an issue.
As for newer connectors, generally they piss me off. I have a 60gb SSD which still works, or would do, if the plastic L key for the power connector didn't snap off, and whilst it has worked for years with a cracked plug, lately a system transplant into a new case, because the new graphics card is 28cm long and wouldn't fit in my old one, means that now one of the pins is cracked. That would have never happened with a molex connector unless I took a hammer and chisel to it, as it happens it snapped as I was trying to fold the cables back.
Same with Microusb. I'm told why it is the new standard connector for phones and not miniusb is that it's designed for the cables to snap before the socket does. Great theroy, but reality is not the case with my phone. Good thing I can swap the batteries out!
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Visionary Tools



Registered: 06/23/07
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you know, before the 7800, I remember I had some graphics card with just one molex power connector. It could have been during the AGP era, or just at the dawn of PCI-E It got me thinking.
Apart from a few places that need 5v or 3.3v, everying in the computer uses 12v. Now, the motherboard connector is fine, it's not changed much except for the addition of +4 to the 20 pin plug, before that was a dreadful AT connector that could be plugged in the wrong way, with [s]hilarious[/s] disasterous consequences.
I don't know what the maximum power draw is designed for the 12v on the molex power connectors, but I do wonder why there's a PCI connector in the first place. It must do something smart. I noticed when I plugged the new graphics card into the motherboard there was a red LED glowing near the PCI-E socket, when I plugged in the power cable it turned from red to white.
It's 3 in the morning and usually I'm asleep by now but it's one of those things that bugs the shit out of me because I'm trying to think what the logic behind it is. Like in Hifi, why there was a move from DIN to RCA connectors, except for a few high end amplifiers that use XLR connections.
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starfire_xes
I Am 'They'



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It is NOT odd that more power requires more ground wires. ALL the current in a circuit flows trhough the ground wires whereas a muti-voltage supply my a lot of current on one ire and little on the others.
The rule of thumb in design (Im an EE, design engineer right now in wireless) is that when you measure current you also measure it on the ground side, not the voltage side. You see this in the way chips are rated, they will state how much current is on the ground pin maximum.
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Visionary Tools



Registered: 06/23/07
Posts: 7,953
Last seen: 1 year, 7 months
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thanks Starfire, that explains it. I've always thought it's a case of pushing current out from positive to negative electrodes.
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