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PCIe Power

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January 22, 2007 2:42:34 AM

I'm building a PC and I ran into a problem that's obscure enough I can't narrow a google search down enough.

Basically I want to get this Mobo

Abit IN9

It has 3 PCIe slots (Two 16x and one 8x bandwidth)
Do I need to buy a PSU that has 4 PCIe power connectors? Or is it kinda like one of those 2 per connector things...?

(I plan to get either an GTX or GTS; however, I'd like to be able to SLI in the future and not kill the third PCI slot. Basically I'd like them all to be powered... :wink: )

Thanks!

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January 22, 2007 3:37:16 AM

Oh, well that's some good info to know, thanks! especially for the really quick answer.

So how (not that I would do this) would one go about getting an SLI setup with a physics card?

Here's my understanding of it, please correct:

One graphics card:
Graphic's card in blue slot (presumably that'd be the 8x bandwidth?)

SLI graphics card:
One card in the top black slot, one in the bottom black slot. (both at 16x bandwidth?)

So it'd be overkill to slap SLI and physics together. Not that you'd need it, but for examples sake. Also, you'd need...5 PCIe power connections assuming the physics card takes one, which I haven't seen from one psu.
January 22, 2007 4:06:11 AM

Quote:
Your PSU only needs as many PCI-e power connectors as your video cards will require. Thee 8800GTX for example needs 2 PCI-e connectors. Now keep in mind that you can't use all 3 PCI-e 16x slots. One if for a single card configuration. You use the other 2 when you want to run SLI leaving the 3rd one blank. So the Blue is single and the black are for SLI. DO not try to populate all 3.


>> Now keep in mind that you can't use all 3 PCI-e 16x slots

bullcrap. There's no reason to not populate all 3 with GPU's if you really want. Actually the middle one is'nt a full x16 slot, its a x8, but you could still put another gpu in it. ...And the 8800gtx has 2 sli connectors too for this very reason.
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January 22, 2007 4:06:57 AM

close, oh so close...

I re-read the PSU 101 (very nice by the way)
I did the calculator thing, and got 534 watts.

534/12 = 44

44 + ~2 = 46 amps. (I chose to add 2 not 4 because the I overestimated on the calculator, ie. GTX when I'm getting GTS)

46/16 = 2.9 so I'd need atleast 3 +12v rails at 16 amps?
46/18 = 2.5 again, I'd need 3 +12v rails at 18 amps, but less stress?
46/20 = 2.something yet again... so I'd need 3 rails again, but much less stress?

I tried hard to read the guide (twice), I just really really don't want to blow up, burn out, or underpower my computer.

Oh, and that specific mobo has two 16x and one 8x, so which do you think is the 8x?
Quote:
Why not? There's no reason to not populate all 3 if you really want. Actually the middle one is'nt a full x16 slot, its a x8, but you could still put another gpu in it. ...And the 8800gtx has 2 sli connectors too for this very reason.

so, if i had one graphics card it'd probably be in on of the black PCIe16...?
January 22, 2007 4:09:13 AM

Quote:
close, oh so close...

I re-read the PSU 101 (very nice by the way)
I did the calculator thing, and got 534 watts.

534/12 = 44

44 + ~2 = 46 amps. (I chose to add 2 not 4 because the I overestimated on the calculator, ie. GTX when I'm getting GTS)

46/16 = 2.9 so I'd need atleast 3 +12v rails at 16 amps?
46/18 = 2.5 again, I'd need 3 +12v rails at 18 amps, but less stress?
46/20 = 2.something yet again... so I'd need 3 rails again, but much less stress?

I tried hard to read the guide (twice), I just really really don't want to blow up, burn out, or underpower my computer.

Oh, and that specific mobo has two 16x and one 8x, so which do you think is the 8x?


On my striker extreme, the two 16s are blue, the 8 is a different color ( white I think.. I dont wanna open my box). The 8 slot is in between the two 16 slots. Hey you could always read the manual....

.. and no, the 8x slot isn't disabled if you populate the two 16x's (at least on my mobo).
January 22, 2007 4:10:54 AM

Quote:
Physics cards are PCI not PCI-e. Besides they are a waiste of money. All they really do is slow your system down in games that can use the card. Physics will be handles byt the video cards themselfs now. Starting with DX10 games and video cards. Also the SLI slots will be the ones running 8x not the single. Physics cards don't need aditional power. They get all the power they need from the motherboard.


why wont you 2k6 noobs stop with the retarded posts, the black ones are for the graphics cards, both running at 16x speeds and the only 8x slot is the blue one which supports the up and coming ati and nvidia physics cards that will most likely soon be released after DX10 is out so please dont say retarded stuff like "physics cards suck and only slow your system down" because that is only true with the current shit physics cards which acctually do nothing for your system what so ever but once real physics cards are released you will most likely see much higher and smoother frame rates since all of the current and future physics calculations will be offloaded from the CPU and GPU to the dedicated physics card and as a whole boosting your systems performance by quite a bit, this will also allow game designers to implement more reactive buildings and other objects to make the games much more realistic in the future so dont be such a noob and get your facts straight, and I own a eVGA 680i mobo so dont try and give me that shit and stop misleading others.
January 22, 2007 4:12:58 AM

No. A single graphics card goes in the top black slot. An SLI pair goes in the top and bottom black slots. Your spare card goes in the blue slot.

The spare card can be used for physics processing or for another display.
January 22, 2007 4:18:45 AM

Quote:
Physics cards are PCI not PCI-e. Besides they are a waiste of money. All they really do is slow your system down in games that can use the card. Physics will be handles byt the video cards themselfs now. Starting with DX10 games and video cards. Also the SLI slots will be the ones running 8x not the single. Physics cards don't need aditional power. They get all the power they need from the motherboard.


why wont you 2k6 noobs stop with the retarded posts, the black ones are for the graphics cards, both running at 16x speeds and the only 8x slot is the blue one which supports the up and coming ati and nvidia physics cards that will most likely soon be released after DX10 is out so please dont say retarded stuff like "physics cards suck and only slow your system down" because that is only true with the current **** physics cards which acctually do nothing for your system what so ever but once real physics cards are released you will most likely see much higher and smoother frame rates since all of the current and future physics calculations will be offloaded from the CPU and GPU to the dedicated physics card and as a whole boosting your systems performance by quite a bit, this will also allow game designers to implement more reactive buildings and other objects to make the games much more realistic in the future so dont be such a noob and get your facts straight, and I own a eVGA 680i mobo so dont try and give me that **** and stop misleading others.

I agree the physx card is a joke. Even an old geforce 3 has more computing power than the Physx card.
I read somewhere that nVidia are planning to include an option in their drivers to allow you to use a 3rd nvidia graphics card as a dedicated physics card. Like when you upgrade your GPU, you can still use your old card to do physics rather than have to toss it.
January 22, 2007 4:22:17 AM

Quote:
Check the specs of the motherboard. If the 2 black slots are enabled then it disables the blue. It won't let you run all 3. It's the limitation of the board. Every SLI board i see will disable one of the PCI-e slots when SLI is enabled.


d00d, don't make me warn you. 680i has all those extra PCIe pathways for a reason.
January 22, 2007 4:25:18 AM

Thanks guys, I think except for that 'how many rails' thing everything is good to go.
I downloaded the manual, and so far I haven't run across anything that says it shuts off the blue 8x slot when in sli mode. Nor does it warn about not using all 3. However, I am still worried about running all three.

Let's say in the future nvidia does either make or allow for old cards to be used for physics and benchmarks suggest they help and I've purchased another GTS to sli. So, I'd have all three slots taken, is 3 12Vrails enough or should 4 be used. Assuming the total watts is enough ~750 W.
January 22, 2007 4:38:28 AM

Quote:
Thanks guys, I think except for that 'how many rails' thing everything is good to go.
I downloaded the manual, and so far I haven't run across anything that says it shuts off the blue 8x slot when in sli mode. Nor does it warn about not using all 3. However, I am still worried about running all three.

Let's say in the future nvidia does either make or allow for old cards to be used for physics and benchmarks suggest they help and I've purchased another GTS to sli. So, I'd have all three slots taken, is 3 12Vrails enough or should 4 be used. Assuming the total watts is enough ~750 W.


I strongly think you're on the wrong track with worrying about rails etc. The number of rails in your psu has nothing to do with the number of slots you use. You could have a PSU with one big rail that all the 12v lines come off for a three gpu system and it would be fine.

The PCI-e specification is very clear about how much power a card can draw from a slot. This is why cards like 8800GTX's have 2 extra power connectors (so they don't exceed the specified power limit for one slot because they get it from the PSU directly).

Any card that doesn't have any additional power connector means it's design ensures it won't ever exceed the allowed power budget for one slot. The motherboard is designed to handle each slot being used and drawing its full power budget all at the same time.

As long as your PSU has enough wattage capacity for everything and enough connectors for all the auxilliary power connectors on all your gpus you'll be fine.
January 22, 2007 4:50:54 AM

Quote:
I downloaded the manual, and so far I haven't run across anything that says it shuts off the blue 8x slot when in sli mode. Nor does it warn about not using all 3. However, I am still worried about running all three.


motherboard manufacturers will most likely be releasing bios and driver updates once the physics drivers are out because I can promise you for a while graphics+physics cards will be a little buggy with games but it will all be sorted out in due time as to how the sorting of calcultations are done to make sure that all physics calculations are going to the physics card and all the graphics calculations are going to the graphics card but eventually it will become streamlined and you will see a deffinate performace and eye candy increase in games which is good for us :D  plus the fact that multi-threaded games will be coming out shortly so Im thinking with all of this extra power availible from processors multi core processors and graphics and physics cards, you will see a big jump in the gaming industry from what we see right now with single threaded games that are optimized for just one graphics card

O and here is something that you might like:

http://www.extreme.outervision.com/psucalculator.jsp
January 22, 2007 4:51:26 AM

Quote:
...As long as your PSU has enough wattage capacity for everything and enough connectors for all the auxilliary power connectors on all your gpus you'll be fine.


Ok, so I could actually get a single rail PSU, as long as that rail has a semi decent amp rating and a proper total Watt number.

thanks for the help!

Quote:

eventually it will become streamlined and you will see a definite performance and eye candy increase in games which is good for us

more foliage = good stuff
January 22, 2007 4:57:16 AM

Quote:
...As long as your PSU has enough wattage capacity for everything and enough connectors for all the auxilliary power connectors on all your gpus you'll be fine.


Ok, so I could actually get a single rail PSU, as long as that rail has a semi decent amp rating and a proper total Watt number.

thanks for the help!

uhh i dont believe thats true. if your PSU was 10,000 watts, but no power was going through the 12v rails, your GPU wouldnt be getting any juice.

if you had one huge 12v rail ~ 40A, that would work, but mutiple rails makes sure for more stability. plus most new PSUs all have mult rails now anyways
January 22, 2007 5:17:29 AM

Quote:

if you had one huge 12v rail ~ 40A, that would work, but mutiple rails makes sure for more stability. plus most new PSUs all have mult rails now anyways


Nope, occasionally the opposite is true though. Nearly all multiple-rail power supplies use a single rail with multiple current limitters (fake separate rails). So none of this "one rail fluctated under load but the other didn't" nonsense. A few have independant rails, but even those have little to no advantage.

The advantage of a single rail is that up to 100% of its power can be delivered to one device set. If you had a 20A graphics/system power requirement and a 10A CPU power requirement, your system could live with only 30A available on a single 12V rail, but it couldn't live with two 18A rails.
January 22, 2007 5:52:58 AM

Quote:


The advantage of a single rail is that up to 100% of its power can be delivered to one device set. If you had a 20A graphics/system power requirement and a 10A CPU power requirement, your system could live with only 30A available on a single 12V rail, but it couldn't live with two 18A rails.


ah i see. so its sort of like with the FAT and such file system. where the cluster size is say 16KB so a file thats 5 KB would take up the whole 16KB cluster.
!