How to know if your PSU can handle a video card?

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V4oLDbOY

Gawd
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Feb 3, 2008
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Just finished my build, no video card. Bought a mobo with on board video since I dont need it now or in the near future really. But I would want to upgrade ram and video card wise later on.

I have a gigabyte MA785GMT-UD2H mobo and a corsair 400CX PSU.

How can I tell what video cards my PSU can handle. Some people rattled off some models in one of my gen hardware threads, but I want to know what to look for when shopping for a video card, not that I want the best my PSU can handle, but I'd like that option.
 
Simple, that PSU is rated @ 30A on your single +12V rail.

I've read that "That power supply needs to have (in total accumulated) at least 40 Amps available on the +12 volts rails" for a 5750 so you wouldn't be able to run that.
 
Here's an old post of mine that dispels the 40A needed for 5750.
Here's my logic:
The 5xxx series is more power efficient as shown in their TDPs (5770 108W vs 4870 150W).
Watts = Amps x Volts

Thus Amps = Watts / Volts
5770:
9A = 108W / 12V
http://www.guru3d.com/article/radeon-hd-5770-review-test/11

4870:
12.5A = 150W / 12V
http://www.guru3d.com/article/amd-ati-radeon-hd-4870-1024mb-review/4
What's odd is they say cross fire is another 150W (which makes sense since the TDP is 150w) and another 8A when my calc shows 12.5.

Of course I'm only looking at the video card's load. But assuming you try each card under the same system setup, the rest of the system power draw will remain the same of course. So how can they say such higher amperage required on the 5xxx series?

Here's a link to show you your Amperage on your 12V rails.
http://www.xtremesystems.org/forums/showthread.php?t=228553

Edit: Also a relevant read:
http://www.tomshardware.co.uk/geforce-radeon-power,review-31495-6.html
Click to expand...

It's out of context but yea you can see it's clearly more power efficient so there's no way 40A makes any sense at all
 
The estimates are generally on the conservative side to remove any liability from the manufacturer.

I run a 5850 on a 300W power supply that only has two 12V rails (14A each). That's with an OC'd quad.
 
V4oLDbOY said:
How can I tell what video cards my PSU can handle. Some people rattled off some models in one of my gen hardware threads, but I want to know what to look for when shopping for a video card, not that I want the best my PSU can handle, but I'd like that option.
Click to expand...

Since you're using a Corsair PSU, use Corsair's PSU finder. Usually a pretty accurate tool:
http://www.corsair.com/psufinder/default.aspx

Just plug in your CPU, # of drives, and what video card you plan on using.
 
friend'scatdied said:
The estimates are generally on the conservative side to remove any liability from the manufacturer.

I run a 5850 on a 300W power supply that only has two 12V rails (14A each). That's with an OC'd quad.
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thats not a normal 300 watt psu by any means. try running that setup on some garbage 300 or even 400 watt psu and you would not make 24 hours if it booted at all.
 
so is there no other programs that can read what your current setup is using power wise?
 
V4oLDbOY said:
so is there no program that can read what your current setup is using power wise?
Click to expand...

Look at the very first reply to your post. Granted it's not exactly accurate and only gives a ballpark range but still is a somewhat useful tool.

Even the Kill-A-Watt is inaccurate:
Paul_Johnson said:
Yes and a quick search would turn up this topic a million times over. Here is the recap:

1) APFC can fool Kill-A-Watts into giving you abnormally low readings (some times giving better than 100% efficiency)

2) Power supplies derate with temperature anywhere from 2w/c above a nominal rated at value to 10w/c.

3) Kill-A-Watt's and most power meters sample too slowly to catch transient loads (the Transient load from our tests is 117w and is COMPLETELY missed by Kill-A-Watts).

4) Power supplies last longer if you stay in the 40% to 60% range of their output.

5) power supplies are quieter if you stay in the 40% to 60% range of their output.

6) Power supplies are cooler if you stay in the 40% to 60% range of their output.

The power meters in UPS software are just as bad. You have to spend some change before you get anywhere near an accurate power meter when your PSU has APFC.
Click to expand...

Here's Paul Johnson's post about the inaccuracy of the Kill-A-Watt:
http://hardforum.com/showpost.php?p=1032190998&postcount=7
 
darkpaw said:
Not really sure how accurate this one is, it told me a I need a 1000 or 1200 for my system heh.

I don't even stress my 750W silence currently.
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yeah your pc likely wouldnt even pull over 350 watts during full system load.
 
DirectorC said:
Most techies buy PSUs that deliver up twice the power they ever actually use (including myself).
Click to expand...

Can you explain why? I'm running an e6600 OC'd to 3.2 & stock 4770 on an Antec Earthwatts 500 PSU. I do it for peace of mind. I'm afraid of failing PSUs. According to Anandtech, the ATI 5850 takes onl 75 more watts during load than my 4770. Later I will upgrade the e6600 to a q6600 and overclock that to 3.2 also. I'll replace the 4770 with a 5850. Antec's calculator says that my upgraded system would draw 420 W (I'm assuming load). The Earthwatts still runs 80+ even at 85% load. Will I have to upgrade? Most people on the forums always encourage you to get more. For stuff like video cards or CPUs where I just lose a little bit of performance, I don't care and am willing to ignore the advice for more. But with PSUs & safety issues, I'm somewhat nervous not to heed the advice for more. I'll probably end up getting a Corsair 620+ PSU for the e6600 & 5850 or hope by the time I do the upgrade (probably not for 18 months lol) but I'd always wonder if I replaced a perfectly capable PSU. 70 bucks would be wasted but I guess it'll give me an irrational peace of mind. Or maybe the new cards by then will be even power efficient and the 500W will comfortably suffice.

I hear few people with 5850s use 500w but that could because people with 5850s (at least right now) are the people who get high end stuff for everything else whether they need it or not.
 
common man said:
Can you explain why? I'm running an e6600 OC'd to 3.2 & stock 4770 on an Antec Earthwatts 500 PSU. I do it for peace of mind. I'm afraid of failing PSUs. According to Anandtech, the ATI 5850 takes onl 75 more watts during load than my 4770. Later I will upgrade the e6600 to a q6600 and overclock that to 3.2 also. I'll replace the 4770 with a 5850. Antec's calculator says that my upgraded system would draw 420 W (I'm assuming load). The Earthwatts still runs 80+ even at 85% load. Will I have to upgrade? Most people on the forums always encourage you to get more. For stuff like video cards or CPUs where I just lose a little bit of performance, I don't care and am willing to ignore the advice for more. But with PSUs & safety issues, I'm somewhat nervous not to heed the advice for more. I'll probably end up getting a Corsair 620+ PSU for the e6600 & 5850 or hope by the time I do the upgrade (probably not for 18 months lol) but I'd always wonder if I replaced a perfectly capable PSU. 70 bucks would be wasted but I guess it'll give me an irrational peace of mind. Or maybe the new cards by then will be even power efficient and the 500W will comfortably suffice.

I hear few people with 5850s use 500w but that could because people with 5850s (at least right now) are the people who get high end stuff for everything else whether they need it or not.
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Nah, the people who go overboard are the ones with 5870s and 5970s. The 5850 is actually a reasonable card as it offers something called value (compared to the 5870 that is, as the 5970 also represents a good value for its target market).

PSUs are most efficient when operating somewhere between 40-60% of its deliverable wattage. Lower usage reduces efficiency substantially, and higher usage reduces efficiency and accelerates the degradation of the PSU's reliable power delivery.
 
friend'scatdied said:
PSUs are most efficient when operating somewhere between 40-60% of its deliverable wattage. Lower usage reduces efficiency substantially, and higher usage reduces efficiency and accelerates the degradation of the PSU's reliable power delivery.
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I saw the benchmark for an Antec EA500. It does 85% efficiency at 60% load (IIRC) but 79% efficiency at 99% load (of course 99% load is bad for more than a brief moment). I'm not sure if 6% efficiency is a big difference. However, I do agree about the degradation. That's a big deal to me. I suppose that's a good enough reason for me to get a Corsair 600+PSU when in fact a 500w could have sufficed.
 
Some valid arguments there, but degradation and efficiency aren't the reasons that fanboys get 1200watt PSUs to power systems that will only see 700watt peak use ;) (and that's with tri-SLI).. I was thinking more like lack of understanding of how much power they will actually use and how degradation and efficiency work, as well as the obvious: e-p33n :D
 
Has anyone compared SiSoftware Sandra Lite's Power Management Efficiency benchmark to a Kill-A-Watt meter's reading?
 
DirectorC said:
Some valid arguments there, but degradation and efficiency aren't the reasons that fanboys get 1200watt PSUs to power systems that will only see 700watt peak use ;) (and that's with tri-SLI).. I was thinking more like lack of understanding of how much power they will actually use and how degradation and efficiency work, as well as the obvious: e-p33n :D
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Why did you choose to go 750W? Headroom?
 
Spare-Flair said:
Simple, that PSU is rated @ 30A on your single +12V rail.

I've read that "That power supply needs to have (in total accumulated) at least 40 Amps available on the +12 volts rails" for a 5750 so you wouldn't be able to run that.
Click to expand...

that's an exaggeration

a good 30A should be fine
 
I've seen numerical comparisons for power efficiency at different loads. I guess it's hard to measure "capacitor aging". Suppose I draw 85% load from my EA500w PSU for 4 hours straight (I never game even close to that long). How much greater is the degradation with that vs. 60% load? Is there a way to monitor PSU "health" or to try out a video card with the PSU ( that meets official specs) and then monitor how it is doing? For example, if you overclock a CPU and it heats to 100C through a temp monitor, then it's easy to say that it's not handling it very well. I'm looking for an analogous way to tell how a PSU is doing. These are lots of questions I know but this is a critical topic and that's why it pops up every week and will continue to do so.
 
I dont understand much or any of what you guys are talking about, but any progress with my question? I'm just curious how I can get a relatively accurate measurement of what my current system uses. I dont want to but a video card and then have it not work, then I'd have to get a new PSU.
 
V4oLDbOY said:
I dont understand much or any of what you guys are talking about, but any progress with my question? I'm just curious how I can get a relatively accurate measurement of what my current system uses. I dont want to but a video card and then have it not work, then I'd have to get a new PSU.
Click to expand...

Plug your components into the link in post #2
 
darkpaw said:
Not really sure how accurate this one is, it told me a I need a 1000 or 1200 for my system heh.

I don't even stress my 750W silence currently.
Click to expand...

Ar you sure you're using the Corsair PSU finder I linked to? I just put your sig rig into the Corsair PSU Finder and it suggested the Corsair 550VX as a minimum. Also, Corsair doesn't have a 1200W PSU.

@ common man
One way to find out the "health" of a PSU is to buy and use a digital multi-meter to monitor the voltages coming from the PSU. Follow the instructions for "Using a multi-meter to check voltages":
http://www.bfgpower.com/troubleshooting.html#DMM

No, there is no software in the world that can monitor PSU health or voltages or anything related to PSU quality.

@ V4oLDbOY
As GonzoP, dinlee23 and myself have pointed out before: use the link in post #2 or the very first reply to your post.
 
Danny Bui said:
@ common man
One way to find out the "health" of a PSU is to buy and use a digital multi-meter to monitor the voltages coming from the PSU. Follow the instructions for "Using a multi-meter to check voltages":
http://www.bfgpower.com/troubleshooting.html#DMM

No, there is no software in the world that can monitor PSU health or voltages or anything related to PSU quality.
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thanks. it's only $30 bucks @sears but more likely the next time i do an upgrade i'll get a corsair 620, 650, or 750w PSU depending on the sale (~60-80 bucks) and fuggedaboutit. no need to think and ignorance is bliss!

but thanks for the wisdom!
 
in this day of efficient, high wattage PSUs, I vote that you buy one with significantly higher wattage that necessary if you have the spare money laying around. It allows you flexibility for any future upgrade while costing you the same, or perhaps even less in electricity. My HX850 is much more efficient than the dell 750 watt I had prior, which actually saves me money on power and gives me upgrade room
 
:confused:
V4oLDbOY said:
I dont understand much or any of what you guys are talking about, but any progress with my question? I'm just curious how I can get a relatively accurate measurement of what my current system uses. I dont want to but a video card and then have it not work, then I'd have to get a new PSU.
Click to expand...

Just count the number of cables in your PSU. No need to get paranoid and get a 1kw one ;)

I had a generic 550PSU that blew up (I've had two PSU's explode on me so far), replaced it with a 550watt PSU that's officially rated for SLI and i've had no problems so far. Few PCs actually uses 300watts. Those benchies you see online (90w-180w-etc) uses the entire CPU, not just the processor. Considering the lowest branded PSU you can find is 550w, you really don't have to think too much unless you're an enthusiast.

How many years does a PSU normally last?:confused:
 
Sly said:
I had a generic 550PSU that blew up
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what was it like for the psu to blow up? i don't know about you but that scares the sh*t of me. i wouldn't even know what to do in the case of an electric fire (certainly not pour water!). i'm so scared of electrical fires that i'll throw away the $70 for a corsair 600+ and have a peace of mind. unless you can enlighten me on how psu's have safety features in the case they do blow up. if a psu failing just meant that my pc would shut down and not turn on - i'd use psu's at 90% load for hours. but the other possibilities are scary...
 
common man said:
Can you explain why? I'm running an e6600 OC'd to 3.2 & stock 4770 on an Antec Earthwatts 500 PSU. I do it for peace of mind. I'm afraid of failing PSUs. According to Anandtech, the ATI 5850 takes onl 75 more watts during load than my 4770. Later I will upgrade the e6600 to a q6600 and overclock that to 3.2 also. I'll replace the 4770 with a 5850. Antec's calculator says that my upgraded system would draw 420 W (I'm assuming load). The Earthwatts still runs 80+ even at 85% load. Will I have to upgrade? Most people on the forums always encourage you to get more. For stuff like video cards or CPUs where I just lose a little bit of performance, I don't care and am willing to ignore the advice for more. But with PSUs & safety issues, I'm somewhat nervous not to heed the advice for more. I'll probably end up getting a Corsair 620+ PSU for the e6600 & 5850 or hope by the time I do the upgrade (probably not for 18 months lol) but I'd always wonder if I replaced a perfectly capable PSU. 70 bucks would be wasted but I guess it'll give me an irrational peace of mind. Or maybe the new cards by then will be even power efficient and the 500W will comfortably suffice.

I hear few people with 5850s use 500w but that could because people with 5850s (at least right now) are the people who get high end stuff for everything else whether they need it or not.
Click to expand...

I ran an Earthwatts 500 for almost 3 years for an E6600 and 8800GTS 320mb, then I swapped to a 4870 and was still running it. It seemed to still be ok, but in some games the graphics card would whine (not a fan whine) which I've heard can be caused by a struggling PSU. I sold my mobo/CPU/ram and upgraded to an i5 system and just decided I might as well get a new PSU at the same time and upgraded to a 650W Coolermaster Silent Pro M, mainly because from reviews it offered pretty good acoustics up to the sort of power levels I'd be expecting to use.

But it was overkill and I knew that when I bought it, just wanted something I wouldn't have to upgrade again if I decide to do a big graphics upgrade and was quiet.

My friend is running an i5 system with a 5770 and 4x hard drives. He was running a 430W PSU (can't remember what brand though) but he started getting issues and upgraded to a Seasonic 430W and it seems to be going strong.
 
Tudz said:
I ran an Earthwatts 500 for almost 3 years for an E6600 and 8800GTS 320mb, then I swapped to a 4870 and was still running it. It seemed to still be ok, but in some games the graphics card would whine (not a fan whine) which I've heard can be caused by a struggling PSU. I sold my mobo/CPU/ram and upgraded to an i5 system and just decided I might as well get a new PSU at the same time and upgraded to a 650W Coolermaster Silent Pro M, mainly because from reviews it offered pretty good acoustics up to the sort of power levels I'd be expecting to use.

But it was overkill and I knew that when I bought it, just wanted something I wouldn't have to upgrade again if I decide to do a big graphics upgrade and was quiet.

My friend is running an i5 system with a 5770 and 4x hard drives. He was running a 430W PSU (can't remember what brand though) but he started getting issues and upgraded to a Seasonic 430W and it seems to be going strong.
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thanks so much for the empirical info. that's a clear answer for me. in the future when i upgrade to the quad and a 5850 (or newer equivalent) - i will upgrade my psu too. this thread has been very informative for me and i think i got all i need. ;)
 
common man said:
what was it like for the psu to blow up? i don't know about you but that scares the sh*t of me. i wouldn't even know what to do in the case of an electric fire (certainly not pour water!). i'm so scared of electrical fires that i'll throw away the $70 for a corsair 600+ and have a peace of mind. unless you can enlighten me on how psu's have safety features in the case they do blow up. if a psu failing just meant that my pc would shut down and not turn on - i'd use psu's at 90% load for hours. but the other possibilities are scary...
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That was a bit of an exaggeration actually. The first one i saw the back of my pc flash, it was raining so i can't say if it actually made a sound, but whatever it was, was bright enough to light the back of my desk.

The second one sounded like a firecracker going off in the CPU (Several loud crackles basically, nothing like a cherrybomb if that's what you're thinking)

Thankfully, both times, my motherboard survived. The only casualty was the soundcard getting bricked on the first one. I still don't know how that happened without harming the mobo:confused:

There really no risk of fire, there's nothing highly flammable in there (capacitors do explode, but they don't propagate a fire), and the whole thing is inside a steel box so if something does catch (maybe the plastic sheaths on the wires?), you'll have plenty of time to put it out without spreading.

In my case, i just pulled the power cords. The insides of the PSU's were messed up, but everything outside was unscathed.




Note that they are generic PSU's that came with the casings. A 550w generic PSU that came with the casing for free should not in any way be compared to a $90.00 550w branded one.


EDIT: One more thing. They didn't really happen without warning. The motherboard utility was reporting unstable voltages maybe a week before they happened. If your 12 volt rail is suddenly reporting 11volts or your 3v rail consistently being off by half a volt, start canvassing for a new PSU.
 
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well I put my setup with a hd 4850 and a phenom x4 deneb, since I plan to unlock once I need too and ended up at 317w with the link in post 2

I dont know if I would need anything better than a 4850.
 
Sly said:
EDIT: One more thing. They didn't really happen without warning. The motherboard utility was reporting unstable voltages maybe a week before they happened. If your 12 volt rail is suddenly reporting 11volts or your 3v rail consistently being off by half a volt, start canvassing for a new PSU.
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To be fair, no software in the world, not even the motherboard BIOs, can read PSU voltages even remotely accurately.

V4oLDbOY said:
I dont know if I would need anything better than a 4850.
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Well what's your max budget for a GPU? What resolution are you playing at. Or are you planning on getting the HD 4850 used? Whether or not you need a faster video card depends on your level of satisfaction with the settings, FPS, and resolution you're getting.
 
Well as far as gaming goes, I will be using a 1900x1080 resolution hdtv. I can handle 720p if that means more FPS. I'd say 30-50 FPS is acceptable as I am used to most console games being locked at 30 fps

my budget is definitely under 100, the further down the better. I dont intend to play crysis or BC2. I was using th3 480 as a referance because thats really the most I intend to spend, newegg has one for $95

I plan to play games like fallout 3 perhaps, new vegas I guess would be included. Maybe some other unique games like the stalker games or cryostasis. But I would honestly want to play games I cant play on consoles. Like civ 5 when it comes out, or maybe even SC2 although I suck at RTSs. I have a ps3 and 360 so I do most gaming on those.

I'd buy used, as long as the warranty is still good and I trust the seller.
 
V4oLDbOY said:
so for a referance, would my PSU be able to handle this gts 250?

http://www.anandtech.com/video/showdoc.aspx?i=3523

I dont understand the chart, is it the total for the entire pc or just the video card?
Click to expand...

The chart is the for the entire PC.

Yes your PSU will be able to handle the GTS 250. BTW, don't pay more than $100 for that card.

Also dude, for the second time, since you have a CORSAIR PSU, you can use the CORSAIR PSU FINDER to determine whether or not your CORSAIR PSU can handle a certain GPU. I linked to it in my first reply in this thread.
 
Danny Bui said:
The chart is the for the entire PC.

Yes your PSU will be able to handle the GTS 250. BTW, don't pay more than $100 for that card.
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Just wanted to use it as a reference as a lot of people seem to recommend the gts 250.

Any other recommendations on possible video cards to shop for?

I am thinking I will just have to pick one out and wait for a sale or deal.

as for the corsair psu finder, the 400w is never an option, the lowest it goes is the 450w. A few video cards give me the 400w, but none if i select a phenom x4. I hope to be able to use the unlocked x2 I have.
 
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