Sign in with
Sign up | Sign in
Your question

Best Gfx Card on 20amps Sli capable?

Last response: in Graphics & Displays
Share
June 6, 2009 9:15:38 AM

I'm upgrading my new system which is three way capable.
But my new 1010W PSU is only 20amp on each rail to the SLI :( 

What is the best GFX cards that will run in SLI Machine of only 20 amps per rail?
9600GT DDR3 Models?

a b Î Nvidia
June 6, 2009 12:31:49 PM

Is this for the rig in your 'more information'?
What resoloution are you/will you be using?
What PSU is it? 1010Watts could run just about any combination that is worthwhile!
June 6, 2009 5:20:01 PM

A 1010 watt PSU? Is that a typo or a new type of PSU I'm not aware of? >.>

Any 1000+ watt PSU will be able to handle pretty much everything you throw at it. You say you have 'only' 20 amps on each rail, and think you can only run 9600 GTs on that. I am happy to announce that you are very wrong about this =)

Depending on what model your PSU is, you could probably run 3 gtx 285s without a hassle.
Related resources
June 6, 2009 10:12:35 PM

Quote:
A 1010 watt PSU? Is that a typo or a new type of PSU I'm not aware of? >.>

Any 1000+ watt PSU will be able to handle pretty much everything you throw at it. You say you have 'only' 20 amps on each rail, and think you can only run 9600 GTs on that. I am happy to announce that you are very wrong about this =)

Depending on what model your PSU is, you could probably run 3 gtx 285s without a hassle.


Brand OCZ 1010W 4way SLi Capable 20A on each 12V Rail

I bought a 9800GT which required 26A on a 12v Rail.
Mine won't do that.

P.s. I also Have a OC Quad Core on board, so lower volts and lower heat may help :) 
June 6, 2009 10:15:33 PM

Never hooked up the 9800GT in fear of hurting the card of my System.
Read manual 1st.
Only realised that it wasn't capable then, assumed 1010W whould be plenty..
Took back for full refund, while I figure out what is best for it..
June 6, 2009 10:29:14 PM

Huh...that really *is* a 1010 watt power supply! Also, I like the emote in the middle of the url =P


Anyway, it's good that you read the manual first and didn't put the card in. That shows you're smart enough to check on things and not just plug things in and expect them to work.

However, when it comes to power requirements on video cards....they are way off. The 26 amps figure that you saw is a more accurate power draw for your entire system, not just your video card. Check out this review that Tom's did on GPU power consumption. The 9800 GT is the exact same as the 8800 GT, so you can look at that card to get your numbers. You'll see that the 88/9800 GT consumes a mere 9.3 amps at maximum load - a far cry from the 26 amps that the box calls for. A gtx 280 consumes about the same amount of power as a gtx 285 (Source: Here), and it looks like a pair of gtx 280s consumes 26.8 amps total. That workload would be a snap for your 1010w power supply.

Now, let's talk about your PSU (or rather, your former PSU >.>). You actually don't have four 12v rails....you have 1. It's just split into four wires coming out of the PSU. Each of those 4 wires is really just a subset of your 12v rail, the total combined power of these wires is your 12v rail strength. Underneath the individual wire ratings, it says 66A for max current. That means 66 amps * 12 volts = 792 watts, so 66A or 792 watts is the maximum load for the 12v rail of that PSU. If you're still confused about this, I recommending reading this long but well-written post that can explain it better than I can.

So, to sum things up: That PSU had a 12v rating of 66a / 792w. A 9800 GT uses about 9.3a / 111w. That PSU is way overqualified to run a 9800 GT, and could in fact run three gtx 285s in SLI, if you decided to. Of course, you have to take into consideration that other components use power (fans, drives, CPU) and then you want to leave a little room for safety, but a 1010w power supply would handle just about anything you threw at it, except for the most extreme of extreme systems.
June 6, 2009 10:44:50 PM

It should be fine with almost anything. While i normally do not trust newegg reviews, people have put quadfire 3870s on it.
June 7, 2009 2:44:49 AM

three gtx 285s?
Aren't they like 30A each = therefore 90A total

How is 20A x 4 = 66A?
(66A Total According to Specs? WTF?)

Here's what i'm already running (powerwise)
All with a Q9550 chip too (95W there i believe)
and on my 790i SLI Ultra Mobo which suggested a 1000W minimum PSU.
5 x 120mm Fans
2 x 80mm fans on case
2 x 120mm fans on cpu heatsink.
Slot Fan Cooler x 1
SATA II HDD
SATA DVD Burner
3x Case LED Lights (RED)

GeForce 9800 GTX SLI (512 MB) 21.4A is more than 20A
So it won't work!!!



June 7, 2009 2:47:08 AM

GeForce 9600 GT SLI (1024 MB) is only 10.4amps
Thats in SLI, guess that is my best?
June 7, 2009 3:24:44 AM

coozie7 said:
Is this for the rig in your 'more information'?
What resoloution are you/will you be using?
What PSU is it? 1010Watts could run just about any combination that is worthwhile!


Yep thats the rig.
June 7, 2009 3:53:37 AM

sirrell said:
three gtx 285s?
Aren't they like 30A each = therefore 90A total


No they're not, read the first link I posted. One gtx 285 uses 17.0 amps. Two in SLI uses 26.8 amps (though they were probably CPU bound and not running at full load)

sirrell said:

How is 20A x 4 = 66A?
(66A Total According to Specs? WTF?)


Each wire from your 12v rail is rated at 20A, but the combined load on all of those wires cannot exceed 66A. All of those wires are hooked up to the same power source - your 12v rail.

sirrell said:
Here's what i'm already running (powerwise)
All with a Q9550 chip too (95W there i believe)
and on my 790i SLI Ultra Mobo which suggested a 1000W minimum PSU.
5 x 120mm Fans
2 x 80mm fans on case
2 x 120mm fans on cpu heatsink.
Slot Fan Cooler x 1
SATA II HDD
SATA DVD Burner
3x Case LED Lights (RED)

Yes, the 9550 is 95w. 95w / 12v = 7.92 amps, so about 8 amps of your 12v rail are going to be used by your CPU. You have a lot of fans and whatnot hooked up, and those could use as much as 7 amps, so that's 15 amps used from your 12v rail. You still have 51A leftover, which is more than enough for a couple strong GPUs.

sirrell said:
GeForce 9800 GTX SLI (512 MB) 21.4A is more than 20A
So it won't work!!!


21.4A for both cards combined - each card is using 10.7A. 75 watts (or 6.25A) comes from the motherboard, leaving each PCI-E connector to supply about 5.5A. Well within the ratings of the individual wires and the 12v rail as a whole.

With so many peripherals hooked up, three gtx 285s is probably iffy, but you could easily do two.
June 7, 2009 4:25:57 AM

Ohh, when you explain it all like that it makes sence to me!!

Thanks Man!!

Now If only I could Afford 1 x GTX 285 LMAO
June 7, 2009 4:32:40 AM

So really I have One 12v rail of 66A
That has been split into 4 outputs.
So 26 amps for a 9800GT wouldn't have damaged things?

Unless I ran 3 x 26 amps = 78amps

Right??

June 7, 2009 4:37:50 AM

sirrell said:
So really I have One 12v rail of 66A
That has been split into 4 outputs.
So 26 amps for a 9800GT wouldn't have damaged things?

Unless I ran 3 x 26 amps = 78amps

Right??


Yes that's correct. You have one 12v rail of 66A that's split into 4 outputs.

Read this review again: http://www.tomshardware.com/reviews/geforce-radeon-powe...

A 9800 GT (aka 8800 GT) only uses 9.3 amps. Ignore the numbers nvidia puts on the box, they're hogwash!


Edit: Ok, maybe don't ignore them outright, but definitely double-check them.
June 7, 2009 4:43:23 AM

How would it be affected if I removed one of the wires/connectors?
Making it split only 3 ways?
Would that give me more amps due to less wire resistance?

(note: its not modular, unplugging is not an option.)
The board is only 3way sli anyway, so i figure removing one won't hurt..
Its never going to be used in this PC.

I have to pull it all apart soon to fit my new heatsink, might do it then.
June 7, 2009 5:43:12 AM

Also If I OC the GFX card with something like Rivatuner, and then benchmarked
would it draw more amps than specified on that toms hardware review?
June 7, 2009 5:43:33 AM

sirrell said:
How would it be affected if I removed one of the wires/connectors?
Making it split only 3 ways?
Would that give me more amps due to less wire resistance?

(note: its not modular, unplugging is not an option.)
The board is only 3way sli anyway, so i figure removing one won't hurt..
Its never going to be used in this PC.

I have to pull it all apart soon to fit my new heatsink, might do it then.


No, it doesn't work like that. Each output of the 12v rail will simply pull as many amps as it needs to. The 12v1, 12v2, (and so on) ratings are just telling you what the safe limits of each output are. GPU and PSU makers know that each output has a limit, so graphics cards start to require multiple PCI-E connectors before come close to overloading a single output.

Edit: Yes, OCed components will have more power draw. It probably won't be by a huge margin, though.
June 7, 2009 5:50:24 AM

Okay so i'll get 3 x 9600GT (DDR3 Models) (best i can afford for now)
and later upgrade that to 2 x 285GTX when they are much older and i can afford them lol

Thanks heaps for all your help
efeat ur awesome!
June 7, 2009 6:04:07 AM

sirrell said:
Okay so i'll get 3 x 9600GT (DDR3 Models) (best i can afford for now)
and later upgrade that to 2 x 285GTX when they are much older and i can afford them lol

Thanks heaps for all your help
efeat ur awesome!


No problem. Though you might want to re-think buying 3x 9600 GTs. The more GPUs you add together, the worse scaling you get. A single gtx 285 would perform about the same as 3x 9600 GTs, and would leave you the option to easily add a 2nd one later.
June 7, 2009 9:02:15 AM

Yep just read this too
http://www.slizone.com/object/slizone_3waysli.html
States:
3-way NVIDIA SLI-Ready GPUs:
NVIDIA GeForce GTX 285
NVIDIA GeForce GTX 280
NVIDIA GeForce GTX 260
NVIDIA GeForce 9800 GTX
NVIDIA GeForce 8800 Ultra
NVIDIA GeForce 8800 GTX

So my selection has been limited even more to the darn expensive range.. lol
I thought all SLI cards were SLI-three way capable
apparently not :( 
June 7, 2009 9:12:38 AM

GeForce GTX 285 video cards require a minimum 550W or greater power supply with a minimum +12V rating of 40 Amps
OMG Damn I couldn't do two of these that's 80A

Right?
June 7, 2009 9:37:19 AM

BTW mine is the 75A not the 66A version.

Which makes me happier again, Might get 2 x 9600GT in SLI and run a third 9600GT with Nvidia PhysiX Drivers
:D 
June 7, 2009 5:51:44 PM

sirrell said:
GeForce GTX 285 video cards require a minimum 550W or greater power supply with a minimum +12V rating of 40 Amps
OMG Damn I couldn't do two of these that's 80A

Right?



No...that's not correct. Again, read this review: http://www.tomshardware.com/reviews/geforce-radeon-powe...

Video cards do NOT use as much power as they claim to need. A single GTX 280 (which has very similar power draw to a GTX 285) uses 17.0A. 80A for two cards would be 80a * 12v = 960 watts of power for the GPUs alone - that's an absurd number and would never work in a real system. Everyone would need 1300W PSUs if that were the case.
June 7, 2009 9:47:56 PM

What that ampage take while the card was under stress (benchmarked)??
or at idle?
June 7, 2009 10:10:49 PM

It was taken at full load.
June 8, 2009 7:11:05 AM

So why are there 1500W PSU's?
If your saying in real systems they aren't needed?
June 8, 2009 7:13:52 AM

I nearly bought a 1500W toughpower thermaltake ESA PSU

Still kinda wish I did.. lol
Grunt grunt more power! lol
!