Can I use a GTX 780 with only the 6-pin power connected?

[suszterpatt]

I got a GTX 780 as a present, and when I went to install it today, I realized that my PSU (Corsair VX450) only has a 6-pin PCI-e connector, while the card has both a 6-pin and 8-pin plug. I'll pick up a molex->8-pin converter in a few days, but in the meantime, can I use the card with only the 6-pin plug connected? Obviously I don't plan on straining the card in any way (no games or anything), if I can just browse and watch movies that's plenty enough.

 

[Grooveriding]

Both power connectors need to be connected. You also need a better PSU for that video card.

 

[Phynaz]

Sell it if you're not gaming on it.

 

[suszterpatt]

Both power connectors need to be connected. You also need a better PSU for that video card.

Will I? The card requires 250W, meaning ~21A on the 12V rail. The PSU provides 33A, and apart from the GPU, all I have in the machine is one SSD (usually under load, has OS/games on it), one HD (just storage), one DVD drive (rarely ever used), and 3 or so low power fans. Even if nVidia was conservative with the power requirement figures (which I doubt), it looks like I have plenty of headroom there.

 

[Magic Carpet]

Will I? The card requires 250W, meaning ~21A on the 12V rail. The PSU provides 33A, and apart from the GPU, all I have in the machine is one SSD (usually under load, has OS/games on it), one HD (just storage), one DVD drive (rarely ever used), and 3 or so low power fans. Even if nVidia was conservative with the power requirement figures (which I doubt), it looks like I have plenty of headroom there.

250w plus extra watts that is lost due to AC/DC conversion. You can certainly try using a molex cable. Personally, I had that PSU and it produced annoying coil whine at higher loads (maybe yours is different). Good luck.

 

[Subyman]

PSUs are rated at what they put out to the components, not what they draw from the wall so AC/DC conversion is taken into account with the rating.

I'm trying to understand what the OP is saying. Do you mean connect only ONE 6-pin? Or do you mean connect TWO 6-pin, but you don't have an 8-pin? If you have two 6-pin, it should be fine. The extra two pins provide two more grounds and let the GPU know the PSU can supply full power, but it should still be usable without them. You shouldn't hurt the GPU trying to boot with only two 6-pin connected. It won't POST if it won't work.

You'll only be providing it with 225W with 2x6pin though, so no heavy gaming. This is NOT a long term solution. You should get a new PSU that is compatible with the card.

 

[suszterpatt]

PSUs are rated at what they put out to the components, not what they draw from the wall so AC/DC conversion is taken into account with the rating.

I'm trying to understand what the OP is saying. Do you mean connect only ONE 6-pin? Or do you mean connect TWO 6-pin, but you don't have an 8-pin? If you have two 6-pin, it should be fine. The extra two pins provide two more grounds and let the GPU know the PSU can supply full power, but it should still be usable without them. You shouldn't hurt the GPU trying to boot with only two 6-pin connected. It won't POST if it won't work.

You'll only be providing it with 225W with 2x6pin though, so no heavy gaming. This is NOT a long term solution. You should get a new PSU that is compatible with the card.

I was suggesting using only 1 6-pin, leaving the 8-pin plug empty. Just as a temporary solution while I get an adapter. I understand now that that won't fly.

In any case, I found some fine print on the manufacturer's site saying that the card requires 42A on the 12V rail (vs my current 33), so I'm off shopping for a new PSU anyway. Thanks for the quick responses all.

 

[lavaheadache]

Running that card with that psu is asking for trouble.

 

[Sable]

And your CPU will be waaay limiting.

 

[escrow4]

This reminds me when I bought a new PSU for a 3930K/Titan build. Had an option for an 850w FSP Aurum or $10 more for 1000w. Both were overkill. I went for the 1000w and have been using it ever since.

For that card, plus seeing as you'd likely want to keep a PSU for a long while, plus accounting for capacitor ageing, I'd recommend something 650w/750w. And yes, heavy CPU bottleneck.

 

[BonzaiDuck]

And your CPU will be waaay limiting.

OP is probably on the right path: searching for a PSU of 600W or more.

I just installed my ASUS 780 GTX card (the glitzy one with the two fans). The card takes one six pin and one eight pin power plug. Some PSUs come with cables that are 6-to-8 convertible -- six pins in the regular plug, and two more dangling by a thread of plastic.

I was even wondering if my Seasonic 750W "X series" was "up to it," but I've been assured.

Truly, this is a powerful card, but I downloaded a new racing-simulation game, and with the card feeding my AVR/HDTV with cable-TV, the GPU usage goes to 100%, the memory usage is more like 50%. I keep wondering if I should've bought two of these monsters, but that's another $500, and the total addition of fans to the system would then be four.

 

[BrightCandle]

That Core 2 Duo is also demanding power from the 12V line to the tune of 130W. 130W + 250W = 380W and your motherboard requires 40W, each RAM stick is 10W and your HDD can pull 10W and ..... it just doesn't fit.

The card can't be run with a 6 pin connector only, it will refuse to start on post without sufficient power connected. If you try and do it with a molex convertor chances are your PSU will just stop working the moment the CPU and GPU pull power. However the PSU could also damage all the components in the computer when it goes depending on the quality of the overcurrent protection and other things. End result = not working PC and potentially lots of broken components.

You need a new PSU, more like a 600W one for such a high consumption card, no ifs or buts about it.

 

[suszterpatt]

Yes, alright, I get it.

I went PSU hunting, see http://forums.anandtech.com/showthread.php?t=2372456

 

[BrightCandle]

I don't know of any reviews of it so I couldn't comment as to the quality of the PSU and its volume. Coolermaster isn't exactly known for PSUs but then I am sure they have many happy customers.

 

[Termie]

Again, OP, if you are just using the system for browsing and movies, you should not use a GTX780. You'll get zero benefit over your existing HD6850. Can you exchange it for another gift that you'll get more use out of?

 

[BonzaiDuck]

Yes, alright, I get it.

I went PSU hunting, see http://forums.anandtech.com/showthread.php?t=2372456

See if you can find a review with a lab test of the CM PSU. Something that analyzes things like voltage ripple. They've been a contender in the PSU business for a while, also making cases and coolers. Lemme get a first impression -- wait a minute . . .

Newegg doesn't have that particular model. Those that they carry have reviews by thousands of customers -- huge samples. The average rating seems consistently around 4 out of 5 or 4 golden eggs.

What is the warranty period offered with the CoolerMaster PSU?

I buy Seasonic PSUs, they've been a consistent icon of quality for years now. But other PSU mfgrs make some good PSUs as well.

 

[suszterpatt]

Again, OP, if you are just using the system for browsing and movies, you should not use a GTX780. You'll get zero benefit over your existing HD6850. Can you exchange it for another gift that you'll get more use out of?

I guess I wasn't clear in the OP, sorry. I absolutely do plan on gaming with the card, I was just asking if it's possible to "cruise along" as it were with just the 6-pin power connected until I sort out the 8-pin connection. Anyway, moot point.

See if you can find a review with a lab test of the CM PSU. Something that analyzes things like voltage ripple. They've been a contender in the PSU business for a while, also making cases and coolers. Lemme get a first impression -- wait a minute . . .

Newegg doesn't have that particular model. Those that they carry have reviews by thousands of customers -- huge samples. The average rating seems consistently around 4 out of 5 or 4 golden eggs.

What is the warranty period offered with the CoolerMaster PSU?

I buy Seasonic PSUs, they've been a consistent icon of quality for years now. But other PSU mfgrs make some good PSUs as well.

The only review I could find that goes so much in-depth is here. I know nothing about ripple measurements myself, but they say the data "gives no cause for criticism". I found a couple reviews that test for simpler stuff like voltage and efficiency, and they all seem to conform to CM's specs.

The manufacturer warranty on the G650M is 5 years.

And I'll just throw this out there: the PC I'm writing this on has been using a CoolerMaster RealPower 450W for a decade, the first half of it as a gaming rig. Still works flawlessly.

 

[Termie]

I see you're discussing a Cooler Master unit at this point, but I'd recommend the Corsair CX500. It's about the same price, and I've used it to power a GTX 780 and 780 Ti with no issues at all. If you'll be getting a new CPU in the future, you can build in some more capacity with the CX600.

And now that you've mentioned you'll be doing some gaming, I'll reiterate what was mentioned above. An e8400 will not support that card. Games will run, but no better than they would on an HD6850. In fact, even that card is severely bottlenecked by an e8400.

 

[Silverforce11]

Have to second Termie, dual core E8400 is just a complete waste for a good GPU.

Sell the 780ti and buy a upgrade MB + CPU combo, with left over cash to get a decent mid-range GPU that willl appreciate the new CPU.

 

[suszterpatt]

So what kind of CPU would be strong enough for that card? More importantly, is there anything with an LGA775 socket that won't bottleneck it, or am I looking to upgrade my motherboard as well?

 

[BonzaiDuck]

Have to second Termie, dual core E8400 is just a complete waste for a good GPU.

Sell the 780ti and buy a upgrade MB + CPU combo, with left over cash to get a decent mid-range GPU that willl appreciate the new CPU.

I think I have to reluctantly side with Termie and Silverforce, but there are plenty of options. I also have a minor shortcoming with my system: it doesn't support PCIE 3.0. But the difference or benefits are fairly insignificant. If your system is based on an E8400, then you won't see the power of the 780 graphics card in that context.

You could sell the card or keep it. If you keep it, start saving some money for current-gen motherboard, processor and RAM.

On the matter of power supply, without reading further the reviews I might find or those linked, sporting a 5-year warranty says a lot according to the old rule-of-thumb about picking PSUs. If they want to minimize their RMAs and replacements from the cost-accountant's point of view, the unit must inspire their own confidence in its design, its durability and probability in general.

 

[Termie]

So what kind of CPU would be strong enough for that card? More importantly, is there anything with an LGA775 socket that won't bottleneck it, or am I looking to upgrade my motherboard as well?

There is nothing on that socket that will properly run a GTX 780. Remember, you're talking about one of the fastest video cards ever made, and a socket that was abandoned by Intel in 2008. Your chip was introduced in January 2008. I remember it fondly...I bought it the month it was released. I ran it with an 8800GT, released in Oct. 2007, which had 1/6 the power of a GTX 780. That was a pretty good match for the e8400.

So, as to the minimum system you'd need to support the GTX 780...I'd say an Intel i5-4570 plus a B85 motherboard, ideally with 8GB of DDR3 RAM. So that's roughly $200 for the processor, $75 for the motherboard, and $75 for the RAM. The total comes to $350, and I'd say it would be money well spent.

 

[suszterpatt]

Yeah, that figures. Curse you, advancement of technology!

Thanks all, you've been a great help.

 

[daxzy]

If you're not gaming, I don't see why you're even bothering with the GTX 780. I'd sell it and pocket the money.

Or I'd sell it, and get a nice upgrade to your current setup. Either go for performance (and power savings) with a Haswell i5/H87 combo or buy a small form factor Haswell based NUC for even extreme power savings.

 

[BonzaiDuck]

If you're not gaming, I don't see why you're even bothering with the GTX 780. I'd sell it and pocket the money.

Or I'd sell it, and get a nice upgrade to your current setup. Either go for performance (and power savings) with a Haswell i5/H87 combo or buy a small form factor Haswell based NUC for even extreme power savings.

But it seems like a catch-22. "Sell the 780 GTX, buy new motherboard, processor and RAM . . . " Graphics card? The OP should also consider keeping the card, selling or recycling her old CPU-mobo-RAM combination, and building a Haswell system with a motherboard that either matches or foresees her needs. This in addition to the PSU.

I hate to see people facing these sorts of crossroads, although I do it all the time. But "all the time" means that I target household hardware for upgrade, schedule the purchases over a several-month time-horizon and take my time putting it together. If a person isn't computer-obsessive, situations like this hit you without warning.