can psu of dell t7400 support a nvidia gtx 690 card ?

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Jo Rotterdam

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I recently installed a GTX 690 in a Dell T7400 . The PSU is a standard Dell 1000 watt unit. I connected the loose 6-pin from the psu to the 690 using a 6-pin to 2 x 8 pin wire. The 690 required 2 - 8 pin connectors.
I find that running the Island demo using both GPUs of the 690 results in a crash. The screen goes black and I can restart the T7400. Using only one of the GPUs the same demo runs at about 100 fps.
I have programmed a scientific problem which runs almost completely on a single GPU. If I run this code I find that at during the most intense part of the computations, the computation speed drops dramatically . After this part it runs normal until it again comes around to the compute intense part.
I have a feeling that this is all due to lack of power available to the GPU. Some benchmarks have set the power consumption for the 690 at aroun 500 watt. I wonder if the PSU which according to the data on the box can produce 18 amps on each cable is really up to it. Maybe I should get me a more modern PSU
Any other ideas ?
Jo
 
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cst1992

cst1992

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That's a very general answer.
The 690 is a 300W card; it requires 25A of current for itself. If two rails with 18A are there for the graphics card, then the total current of 32-35A is enough to power the 690.
 
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Brantyn Gerik

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the 690 is indeed a 300 watt card, but requires more current due to using two gpu on one board. nvidia recommends 42 amps for a single 770. yes this is overkill, but considering the 690 is essentially 2 770's on one board (the 770 is just a rebranded 680) the power draw is higher than that of a single card, and higher for different reasons than just raw power needed by each chip. Another thing with these low quality power supplies is that it may actually have up to 4 12v rails, but each one is severely under-powered for these types of high end gpu's. You also have to realize that this psu is not a quality one, and thus should NOT be expected to perform to specifications at all times (usually they list peak power usage rather than continuous). this psu does not even have all of its' important specs on the site, which is highly indicative of how low quality it truly is.
 
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cst1992

cst1992

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I don't trust ebay to list specs properly -- ever.
42A is generally recommended for a 250w card such as the 780Ti. The 770 is a 195W card and will require a 37A current on the +12V rail.
I don't get what you're saying about the 4 rails. Sure, they should not be used to their full extent, but if the power connectors are not internally connected to a single rail, then it's fine running a graphics card such as the 690.

Another thing is that the labeled wattage is what is overstated; not the current ratings(eg a 30A power supply is actually 360W even if the manufacturer states it as 450W in which case he's either testing at low temperature or listing peak power or both).

And you're right about the PSU not to be expected to run at full load at all times, it's a cheap PSU.(however it's said that its output from all 5 rails is around 79A which is not bad for a 1000W PSU).
 
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Jo Rotterdam

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Thanks guys for your input. From the figures on the power consumption for the 690 it does begin to look as if the PSU might need to be replaced with a modern version which carries a bit more punch on a rail. I'll start looking. Bi for now !
 
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Brantyn Gerik

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cst1992

this power supply may have up to 4 12v rails, but each 12v rail may only output 18 amps depending on how low quality it is. This is an optimistic guess as to the strength of the 12v rails in this psu. They are not connected back to a single rail, so you need to find a way to get them all to run to the 690 (requires some really funky connectors sometimes). If you can only get 2 rails to go to the 690, then you are going to be underpowering the card as it is the highest power consuming card aside from the 7990. It Will use over 300 watts, which is a lot more than what 2 low quality 12v rails at 18amps will be able to sustain. if you can find a way to get at least 3 rails to power the gpu, then you would be fine, but if you cannot do this, you WILL have to replace the power supply or go buy some connectors


If you look how op has initially connected it ,he used a 6 pin to 2x8pin, meaning he was trying to run the gpu off 1 12v rail. if he can use 2 rails he MIGHT be ok, but the safest option would be to see if he can get adapters to allow him to use at least 3 of the 12v rails. It is possible, but it can just be a big confusing process and it often makes a mess of your wiring
 
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Jo Rotterdam

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I took some time to think about the way out of this and finally got in touch with a local hardware store. I am not sure about all the colour coding of the rail wires so I got help on this. They pointed out that there was a second rail available among the spagetti. I hooked it up and sure enough, it worked. The island demo (waves around an island) ran with both GPUs going at 98% ! So , power problem solved without buying a new PSU !
Second problem concerning the performance drop during heavy computations may be something I did myself i.e. my code was compiled for a TITAN with a higher compute capability than the 690 (3.5 against 3.0). I will recompile and see if that had anything to do with it.
For the present, thanks for all your suggestions, and regards,
Jo
 
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