New Computer Build Power Requirements

milehigh

Just looking at an order I'm about to place, seeing that my chosen video card requires:

Minimum of a 550 Watt power supply. (Minimum recommended power supply with +12 Volt current rating of 38 Amps.)

Right now I have an Antec True Power 550W PSU. The specs are listed here:

http://www.antec.com/specs/TPII550_spe.html

It seems to list 2 +12V items, both with 19A ratings, combining for 38A, but I really don't know how to read these things. So, I come here again, asking WILL IT BLEND?....err, process....

For the record I'm combining this with an Intel I7 950 and am only running one card.

altmann

So the end result is 2 GPUs or one?

See, here's the fucky shit with PSUs, most shitparty (3rd party) PSUs are "rated" really high, like "Whee 550 watts!" but that just about means they managed to hit 550 watts in a frozen meatlocker before the thing fucking exploded.

The main issue with PSUs that you REALLY need to worry about is NAME. Seriously, the name is almost as important as the watts, hell, it IS more important. Go with an Antec 550, you'll be ok. Antec, Corsair or OCZ and you'll be ok.

Don't buy a cheap PSU. If anything, you can buy a really good one, and use it for a REALLY long time.

vonPoonBurGer

My guess is that the power supply you have is fine, but it all depends how much load you end up putting on a single 12V rail. From the manual, I can see your PSU has one PCI-E 6-pin connector. That 6-pin connector is on one of the two 12V rails, but who knows which one? The manual doesn't have a table to say which rail the various +12V connectors are using. If the video card you've selected requires two 6-pin PCI-E power connectors, you'd have to use a 4-pin Molex to 6-pin PCI-E connector to supply the card. If you happen to pick a 4-pin Molex plug that's on the same rail as the one 6-pin PCI-E connector, now you've got your whole card running off a single rail. If you have a hard drive, a DVD-RW, maybe some other stuff on the same 12V rail, you're at risk of hitting the amperage limit on that rail, which will cause the PSU to do a safety shutdown.

OnTheLastCastle

Never skimp on a PSU. I like Antec, but I'd still want more power than the minimum requirement. I think I rock a 700 or 800.

If you have problems with freezes, it's probably the PSU.

milehigh

Looks like I will upgrade the PSU. However the guys at the computer place over here (Microcenter) told me that there was no way a 550W would even boot the system, since that's supposedly the requirement for ONLY the graphics card. The box however said (550W minimum required, based on system running Intel 3.2Ghz processor), so I'm not entirely sure. It seems as though you can't run a video card independent of the rest of the system so that number would be based on some type of full configuration. I'll upgrade either way but it seems like they may have been exaggerating for the sake of the sale.

Cabezone

http://extreme.outervision.com/psucalculatorlite.jsp

http://www.thermaltake.outervision.com/

splash

milehigh wrote: »

However the guys at the computer place over here (Microcenter) told me that there was no way a 550W would even boot the system, since that's supposedly the requirement for ONLY the graphics card.

ummm no :rotate:

vonPoonBurGer

milehigh wrote: »

However the guys at the computer place over here (Microcenter) told me that there was no way a 550W would even boot the system, since that's supposedly the requirement for ONLY the graphics card.

Those people are either a) woefully ignorant for computer store staff or b) trying to sell you far more PSU than you need. Your card's maximum power draw depends entirely on how many and what type of power connectors it has. The maximum power that can normally be supplied by a PCI-E slot is 75W, a 6-pin connector can supply another 75W, and an 8-pin connector can provide 150W. So if your card has one 6-pin and one 8-pin connector, it could pull at most 300W (75+75+150). Most cards I've seen have one or two 6-pin connectors, i.e. most cards are 150W or 225W at most. That's not a hard limit, it's just the maximum amount those connectors are supposed to provide. You can sometimes see cards slipping a little over the total envelope, but not by much.

The reason video card manufacturers throw out guidelines like "550W" is because that recommendation provides a reasonable certainty that there's enough total 12V capacity in that PSU to run their card. Where users often get into trouble is when they inadvertently put too much load on a single 12V rail with limited (20A or less) capacity. Even though they're within their PSU's total power capacity, they're tripping the 12V rail overcurrent protection circuitry in their PSU, causing the system to suddenly power down when they put it under load. The maximum power on one of OP's 12V rails is 12V x 19A = 228W. If OP has a card with two 6-pin connectors and things are wired up such that the PCI-E bus, the two 6-pin connectors and other devices besides are all pulling from one 12V rail, it'd be easy to trip the limiter circuitry when the system is put under load. Exact same card, exact same PSU, but the 12V-using devices are split roughly evenly across the two 12V rails? No issues at all.

milehigh

vonPoonBurGer wrote: »

milehigh wrote: »

However the guys at the computer place over here (Microcenter) told me that there was no way a 550W would even boot the system, since that's supposedly the requirement for ONLY the graphics card.

Those people are either a) woefully ignorant for computer store staff or b) trying to sell you far more PSU than you need. Your card's maximum power draw depends entirely on how many and what type of power connectors it has. The maximum power that can normally be supplied by a PCI-E slot is 75W, a 6-pin connector can supply another 75W, and an 8-pin connector can provide 150W. So if your card has one 6-pin and one 8-pin connector, it could pull at most 300W (75+75+150). Most cards I've seen have one or two 6-pin connectors, i.e. most cards are 150W or 225W at most. That's not a hard limit, it's just the maximum amount those connectors are supposed to provide. You can sometimes see cards slipping a little over the total envelope, but not by much.

The reason video card manufacturers throw out guidelines like "550W" is because that recommendation provides a reasonable certainty that there's enough total 12V capacity in that PSU to run their card. Where users often get into trouble is when they inadvertently put too much load on a single 12V rail with limited (20A or less) capacity. Even though they're within their PSU's total power capacity, they're tripping the 12V rail overcurrent protection circuitry in their CPU, causing the system to suddenly power down when they put it under load. The maximum power on one of OP's 12V rails is 12V x 19A = 228W. If OP has a card with two 6-pin connectors and things are wired up such that the PCI-E bus, the two 6-pin connectors and other devices besides are all pulling from one 12V rail, it'd be easy to trip the limiter circuitry when the system is put under load. Exact same card, exact same CPU, but the 12V-using devices are split roughly evenly across the two 12V rails? No issues at all.

So much good info here, thanks much. I had a feeling they were trying to upsell me on the PSU so I left. Came back and found that my CPU wasn't as outdated as I thought and instead decided to just upgrade my RAM, video card (GTX 460) and get a new hard drive. Getting ready to put it together now, should be solid on the power requirements, but the above (all the info here really) is going to be great the next time I need to look at upgrading the full thing. Thanks all!

Satsumomo

Card manufacturer specs always include other system components (My MSI card for example says it requires 30A or something, and it says "This is for a system running an i7 920, your actual requirements may vary") so it's just so you don't get enough juice for the card only.

As I see it now, your 550W system just barely has enough power for your system, and you would be better off getting a few more watts in there.

StrifeRaZoR

I had this exact same issue about a week ago. My 600w PSU exploded (It was an ULTRA) and I was without a desktop system for a few weeks. I was browsing around trying to find a new PSU in time for the holiday deals, but was unsure of what my system actually required. It says that my video cards (8800GS Alpha dogs) require 430w of power. Well, I have two of them, and I know for a fact that both of them did not require 860w combined, as they were working just fine with 600w. I used the link that Cabezone provided above to actually see what was required. Apparently my system would but and run under 80% load with 340w. So 600w was almost overkill.

I found a very nice RAIDMAX 630w Modular SLi PSU on NewEgg for like, 35$. It's an AMAZING PSU. I love the modular design, and it's even letting me overclock these ancient 8800's to 15% without even breaking a sweat.

Tofystedeth

I've actually had decent luck with cheap PSUs, but then with the systems I've built, even if I account for like, a 30% fudge factor on the wattage they give, it's still overprovisioned for the hardware in the box. But that's hoping the other role of the PSU (last line of defense between your system and a power surge) works.