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I've been trying to research my way into a new graphics card lately. I've decided i want the NVIDIA GeForce GTX 770 but am questioning a new power supply.

At the moment I have a Dell XPS 8700 with a power supply of what I believe is 460 watts.

How can I determine what wattage I need? Also does amperage play a role? If so, what might I need to determine that?

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To improve your question, I edited it so it doesn't sound too much like a product recommendation request. – CharlieRB Dec 31 '13 at 20:03
This information normally is located within the manual. I have serious doubt about a 460 Watt Powersupply being enough for that card. You can look at pretty much any GTX 770 OC card to determine what the power requirements MIGHT be or contact MSI directly. – Ramhound Dec 31 '13 at 20:07

2 Answers 2

up vote 1 down vote accepted

The wattage you need is simply more then the maximum the system will draw, with a bit of a buffer. Your current 460 watt power supply might be enough (just), but you probably want a 550 watt or better power supply. [ The video card you are using requires about 285 watts of power by itself, so the most you could need would be 745 watts, but thats excessive for your requirements]

This link may be relevant as apparently the Dell believe the GTX760 mentioned in the post would be OK with this system. While I agree with poster that it would be marginal the XPS8700 appears to have very low power requirements (as is the case with many systems running newer Intel chips).

Looking at the specs for the system, it appears that it can was designed to accept up to a 225 watt graphics card (but the default system maximum power consumption was not specified), so getting an extra 100 watts on the power supply should be ample.

To answer your question about wattage and amperage - Watts = AMPS * Voltage, so more amps is the same as more watts. A system will only require the amount of amps it requires, so overspeccing the PSU won't hurt your system, only your wallet. I'd recommend an 80+ PSU as they are more efficient and generally made out of better componentary - often a smaller 80+ PSU will give more reliable power then a cheap high power rating unit.

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I hope you don't mind, I corrected the power supply value in your answer, I would agree it would be margiinal. I honestly also have serious doubts he would even has access to the two required 4 pin PCI-E power connectors to be honest. – Ramhound Dec 31 '13 at 20:15
Sorry, I saw that - but I was busy editing the answer to be more complete as I found more details about the host system. Thanks for helping ! – davidgo Dec 31 '13 at 20:16
I agree that component quality is the main factor. You can also push high-quality components pretty hard -- near their design limits -- for an extended period of time without experiencing any ill effects, except perhaps reduced efficiency... whereas with a poorly designed component it can fail even within "normal" operating parameters. – allquixotic Dec 31 '13 at 20:48
thanks, and i should have known the amperage thing, i feel stupid for asking about it now. Thanks for the help! edit: one other thing; im planning on upgrading in the future so would it be good to spend the extra money now and get a 750 watt or just stick with a 600? – Ozay34 Dec 31 '13 at 22:48
Question is how are you going to upgrade ? From the pic on the Dell design site I'd say your upgrade options are limited (1 free PCI-e slot ?). Other then the cash outlay there is no harm in getting a bigger PSU, but be aware that some PSU's will waste quite a bit of power if over-specced (which is where 80 Plus Platinum/Titanium might be worth looking at - crunch your numbers !) That said its often worthwhile to get a higher specced one if they are the same range but only a few dollars more expensive - again though - quality is way more important then stated output. – davidgo Dec 31 '13 at 23:33

The graphic card should specify how many Watts it need and then you need to add that number with what your system is already using minus the graphic card already in your system. It is simply a matter of checking out each component you have in your computer system, checking how many watts they need and add them together.

Watts equals Amps times Voltage and the voltage is fixed to +5 or +12 Volts, so yes, Amps play a role, but it is covered by the fact that if the power supply is big enough in terms of Watts, the amps will be enough to.


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