Hi all! Hoping I can pick some of your brains for a bit!

I'm looking at building myself a new computer, as my laptop is getting a little long in the tooth, and my netbook is better for use at uni anyway.

Anyway, I think I've worked out what I'm after in terms of hardware, it's the PSU that's getting me puzzled.

The CPU I'm after has a TDP of 125w if it matters.

I'm looking a GTX560 (ti, maybe) GPU at first, with the intention of later SLI'ing them later on once I've got a bit more spare money.

One GPU needs 170w, and at least 500watts for the system overall. I'm guessing that I'll need a spare 170w capacity for when they've been SLI'ed?

I'm looking at this PSU, which claims to be SLI capable.

So, my thoughts are: I've got 600watt capacity - 125 for the CPU - 170 for one GPU, and - 170 for the other, which leaves me with 135 'spare' watts (although of course HDD, DVD, fans etc will take some of that).

(600 - 125 - 170 - 170 = 135.) Am I right so far?

If so (which is unlikely I guess!), how do I work out the power for the 12v rails? The PSU people claim 25v per rail. Can I just add these to get 50a in total? (I think the GPU needs 30-40, but I've not found out for certain yet.)

http://www.ocztechnology.com/images/awards/mxsp_wattage_charts.jpg

And the final questions. That PSU has enough plugs to power one GPU. If it claims to be SLI certified, presumably it's able to power a second. How?

If the GPU needed only 20a, then I could do it using just one 12v presumably, using the other one to power something else, rather than having to plug them both into one card?

Thanks for any help/clarification!

Joe

Hi all! Hoping I can pick some of your brains for a bit!

I'm looking at building myself a new computer, as my laptop is getting a little long in the tooth, and my netbook is better for use at uni anyway.

Anyway, I think I've worked out what I'm after in terms of hardware, it's the PSU that's getting me puzzled.

The CPU I'm after has a TDP of 125w if it matters.

I'm looking a GTX560 (ti, maybe) GPU at first, with the intention of later SLI'ing them later on once I've got a bit more spare money.

One GPU needs 170w, and at least 500watts for the system overall. I'm guessing that I'll need a spare 170w capacity for when they've been SLI'ed?

I'm looking at this PSU, which claims to be SLI capable.

So, my thoughts are: I've got 600watt capacity - 125 for the CPU - 170 for one GPU, and - 170 for the other, which leaves me with 135 'spare' watts (although of course HDD, DVD, fans etc will take some of that).

(600 - 125 - 170 - 170 = 135.) Am I right so far?

If so (which is unlikely I guess!), how do I work out the power for the 12v rails? The PSU people claim 25v per rail. Can I just add these to get 50a in total? (I think the GPU needs 30-40, but I've not found out for certain yet.)

http://www.ocztechnology.com/images/awards/mxsp_wattage_charts.jpg

And the final questions. That PSU has enough plugs to power one GPU. If it claims to be SLI certified, presumably it's able to power a second. How?

If the GPU needed only 20a, then I could do it using just one 12v presumably, using the other one to power something else, rather than having to plug them both into one card?

Thanks for any help/clarification!

Joe

OK firstly don't scrimp on PSU purchase, even if you are building a budget system. An underpowered PSU can cause lots of knock on effect problems which can be very easily put down to failing GPU, mobo, etc.

You mention a GTX 560 with the intention of possibly SLIing down the line, not a bad plan but a dual GPU set up comes with extra problems, let alone power requirements. Firstly, I would consider 600W to be a bare minimum for a single GPU system. Also I would look at a Corsair PSU rather than OCZ. I have found OCZ to not be so hot on equipment in the last couple of years, but Corsair generally have excellent write ups. To put PSU requirements into perspective, I had a GTX 580 and a 750W PSU, and under load the PSU would struggle, and by struggle I mean get hot and the fan would increase in speed in vain to try and keep it cool. I have since upgraded to a Corsair TX850 and the difference is massive... was definitely worth the extra money.

I would personally not spend your time "adding up watts" so to speak, because difference branded PSUs output different watts and more importantly amps on the 12V rail (important for GPU), and some are even tested and certified in unrealistic conditions as to falsify certification.

You are best off looking at reviews, user opinions etc and doing as much research as possible, but to save you the time of doing this I would recommend a Corsair 600W bare minimum for single GPU, or 750W plus for a dual GTX 560 set up.

Also, you will find that most enthusiast/gamer PSUs will come with 4x PCI-e power ports, most definitely the 6 pin iteration but also usually the 8pin iteration as well for high end GPUs like the GTX 580, so I wouldn't worry about the plugs Reading reviews on forums and tech websites will often show full details of the PSU including all the connectors etc as well which will help put your mind at ease.

Seriously, just get the best PSU you can afford, imo it's the single most important component (and funnily enough the most overlooked) in system building, and that's an opinion forged from 6+ years of building many many computers...

I've probably digressed a bit in this but feel free to repost and I will do my best to clear up

HTH

Thanks, that seems to be something there is much debate on other forums too - although I'm inclined to go with your view and not skimp on the PSU - like tyres really, while cheap ones will work, would entrust your car (PC) to them!?

One area that does baffle me a bit though - a friend recently got a GTX460, and a PSU, which I fitted for him yesterday (having never tried before). At first, we only plugged in one 12v rail, as that's what the box said it needed, and I didn't want to blow it up. Nothing happened, it wouldn't boot the GPU. We plugged the second 12v rail in, and it worked. Is that because the current down one 12v rail wasn't enough, and as such it needed 2 to get the amperage high enough? If so, would a PSU with enough amps on the 12v rail, only need one plug to be used on the GPU, meaning I could away with just two PCI-e plugs? While I take your point about the 4+ pins on better PSUs, it's more for my own piece of mind, and to try and prove a theory!

Make and power aside, these would both be OK on the connection front wouldn't they?

http://www.coolermaster.com/product.php?product_id=6642 Will have enough power on the 12v rails to power a GPU without needing both to be connected, meaning I can use the second 12v rail on the 2nd GPU?

http://www.ebuyer.com/229934-arctic-power-pro-750w-modular-14cm-fan-psu-4x-pci-e-8x-arctic-pro-750w-cm and that one's got 4 connectors so even if one 12v rail is a bit down on amps, the other will boost it back up again?

What do you think of the AP ones, as that is about as much as I'd like to spend ideally (although it might be cheaper elsewhere).

Thanks for your help, it is appreciated! This is one of the areas of computers I've never got into before, as I've always owned laptops.

Joe

Just a input when getting a case my Aztec case puts the psu at the bOttom of the case which makes it easier, I use a 650 cosair psu and my graphics card is a ati radeon 6770 hd card, I've heard that cosair are very good with reliability, and that you can't go wrong, and to be honest there not that much more than the other brands anyway.

Yes, exactly like tyres in my opinion

Yeah that's not a rare thing. A lot of motherboards I've encountered won't turn on/POST unless you have both 24 pin and 4 pin power connectors connected. And I don't think it quite works with that with the rails, if the GPU has 1 PCI-e power port, plug it in, if it has 2, plug them both in

The GX 650 is fine on the connection front. Like I mentioned, it has 2 x 8 pin PCI-e power ports, so you will be able to run one GPU absolutely fine. The 650 Coolermaster should be fine. I actually had a Coolermaster GX750 and it ran 2 x Radeon 5850s in crossfire fine... just about. I wouldn't like to put a higher end card through it. If you can afford it, get a 700+ one but I think a 650 would be fine for your GTX 560.

I've not encountered Arctic Pro before to be honest in the PSU world. Although one thing I would point out is that a reputable brand PSU of lower wattage, e.g. Corsair 600W, is most certainly better than say a poor/generic brand PSU of say 750W. The brand and quality make a massive difference, more so than the actual wattage.

I'm running an overclocked GTX 560 Ti at the moment, 850w Corasir PSU. Overkill at the moment, but it's a worthwhile investment.

You need at least 20 amps on the 12v rail to power this card, so take that into mind. I had to upgrade my good, but "old tech" 850w Antec Trupower as they weren't designed for so many amps on the rails "back then"

Thanks guys.

So far, based on what you've been saying I've provisionally landed on this or this one.

I'm leaning towards the 800watt one; 65watts down the 12v rail, with 4 PCI-e plugs, with 'spare capacity', and a decent make, and only £6ish more than the 750watt one - think I'd rather pay the extra to upgrade it again in a couple of years time (and it comes with LED's! [/child]).

Sounds good

Excellent choice on the Corsair

Good too hear it's approved of.

Now, to try and find some money for this. . . . wonder how generous student finance are feeling. . .

Thanks again for your help - managed to clear up in an hour or two what the rest of the internet failed to do completely!

Good too hear it's approved of.

Now, to try and find some money for this. . . . wonder how generous student finance are feeling. . .

Thanks again for your help - managed to clear up in an hour or two what the rest of the internet failed to do completely!

Don't complain about being a broke student, not if you're even considering this

Placement year

Might as well make the most of it before going back to uni. (Still get student finance money, just they don't issue grants, which is pretty fair IMO.)

one thing i dont quite understand with psu's

all components are using less and less power on each of their incarnations, whether it be cpu or gfx, yet we keep buying bigger and bigger psu's which i just think is overkill ( my opinion not everybodys ) and paying extortionate prices for the privilege :wonder:

for example i have one pc that has a o/c core2duo, 4gb ram, nvida 575 gfx, several hdd's, dvdrom fans etc etc all running happily on a hyper true power 480 watter, go figure and has been for about 4 years, never missing a beat

all id say on psu's is buy a reputable brand and if space could be tight then get modular one

now cases, thats where its at, crap case = crap cooling = meltdown

Edited 11 November, 201114 yr by the mad monk

one thing i dont quite understand with psu's

all components are using less and less power on each of their incarnations, whether it be cpu or gfx, yet we keep buying bigger and bigger psu's which i just think is overkill ( my opinion not everybodys ) and paying extortionate prices for the privilege :wonder:

Not quite sure how you've got this impression? Without getting into a huge tech flame war, it was my understanding that as technology advances, the key factors in driving the components are the power required and heat generated. Even Moore's law states that in a given time frame the number of transistors on a circuit will increase exponentially, thus surely so should the power requirements roughly follow suit.

Although I agree in principle in what you're saying, in that in the modern age there seems to be so many people with literally way too much money completely going overboard on PSU requirements. For instance you see tech enthusiasts going out and buying 1000W PSUs for single GPU rigs, which is complete overkill by about 400W.

Having said that, 480W does seem very low for your build, even for a decent branded PSU. Do you not have any problems with the amount of heat generated by the PSU, which would be an indicator of the stress it's under?

to be fair mate i dont monitor anything, i just use it, well the kids more than me and its used a hell of a lot between us

i couldnt tell you this or that about it and to be honest does mr average need to know that? just so long as its quality itll be fine

i did stress about cooling in my post as i see that as, if not more so, important

each incarnation of gfx cards rants on about the lower power requirements they use as they become more efficient, again providing the cooling is adequate, so is there any need to keep going bigger and bigger

i just think folks go overboard and power hungry, quality is the key

You have a point, with most average systems 400-50 will do, it will also run quite a few quad processors, but with graphics cards they do require quite a bit if power, mine suggests 500 watt I think so I went 650, my motherboard is very Eco friendly, but with very powerful systems you will need to have big power, especially when crossfiring 2 cards.

I think with today's CPUs they really are pushed quite hard with today's games, games arnt really touching the high end cards yet, but they are getting near with CPUs, so again if you don't use your system for highend games you won't push your CPU much, but experts say at least 3 cores are best for today's games.

james - BF3 is pushing graphics cards!

Metro 2033 was also pretty harsh on them!

I think with today's CPUs they really are pushed quite hard with today's games, games arnt really touching the high end cards yet, but they are getting near with CPUs, so again if you don't use your system for highend games you won't push your CPU much, but experts say at least 3 cores are best for today's games.

I was looking at the BullDozers, the 8 core AMD things. Only £160, so less than most i7s and cheaper MBs!

Overclockable to 8.5Ghz if you've got a vat of liquid nitrogen (which, surprisingly, I don't!).

Edited 12 November, 201114 yr by TriggerFish

I think with today's CPUs they really are pushed quite hard with today's games, games arnt really touching the high end cards yet, but they are getting near with CPUs, so again if you don't use your system for highend games you won't push your CPU much, but experts say at least 3 cores are best for today's games.

Download yourself a copy of Unigine Heaven, run the benchmark and then tell me that high-end cards aren't utilised yet . That benchmark brings my rig to a sub 30 fps stutter and I'm running an i7 950 and a GTX 580. Also with the introduction of CUDA etc, GPUs are being used even more as developers look to offload tasks that aren't directly related to graphics rendering to the GPU (such as collision detection) to free up CPU cycles.

james - BF3 is pushing graphics cards!

Metro 2033 was also pretty harsh on them!

True story. Metro 2033 is a beast.

Ahh sorry when I say high end I mean the uber 6 series ati card and the 700 quid i7 my friend had to much money and loves his computers, as far as I know nothing is touching anywhere near it, I'm no expert by the way, just saying my thoughts!

goes back to my point about going power hungry, doesnt matter which part, you can go overboard on every piece of the computer

ive two oldish ( about 3-4 years ) pc's that still show high/ultra on bf3, id just buy what you can afford with upgrading always in mind

thats unless your flush with cash and then just buy the most expensive

Tbh if you are going to get a new graphics card then hold off a bit longer, the new ATi 7 series cards should be out in December.

There's also a big difference between peak and average power used by components. When sizing up a PSU you need to look at peak power - not average. The ratio between the two is greater now than it used to be as manufacturers try to reduce average power consumption with power saving modes, etc.

Hi all! Hoping I can pick some of your brains for a bit!

I'm looking at building myself a new computer, as my laptop is getting a little long in the tooth, and my netbook is better for use at uni anyway.

Anyway, I think I've worked out what I'm after in terms of hardware, it's the PSU that's getting me puzzled.

The CPU I'm after has a TDP of 125w if it matters.

I'm looking a GTX560 (ti, maybe) GPU at first, with the intention of later SLI'ing them later on once I've got a bit more spare money.

One GPU needs 170w, and at least 500watts for the system overall. I'm guessing that I'll need a spare 170w capacity for when they've been SLI'ed?

I'm looking at this PSU, which claims to be SLI capable.

So, my thoughts are: I've got 600watt capacity - 125 for the CPU - 170 for one GPU, and - 170 for the other, which leaves me with 135 'spare' watts (although of course HDD, DVD, fans etc will take some of that).

(600 - 125 - 170 - 170 = 135.) Am I right so far?

If so (which is unlikely I guess!), how do I work out the power for the 12v rails? The PSU people claim 25v per rail. Can I just add these to get 50a in total? (I think the GPU needs 30-40, but I've not found out for certain yet.)

http://www.ocztechno...tage_charts.jpg

And the final questions. That PSU has enough plugs to power one GPU. If it claims to be SLI certified, presumably it's able to power a second. How?

If the GPU needed only 20a, then I could do it using just one 12v presumably, using the other one to power something else, rather than having to plug them both into one card?

Thanks for any help/clarification!

Joe

Trigger, you can easily calculate your power needs by using one of the many online power supply calculators. OCZ have one on their site but you can do a google and find loads. They let you enter in what grahic card/s you are planning on using and of course cpu, dvd's, fans etc. It allows you to see what your average loading will be and make allowances for SLI and peak game demands etc. I build loads of computers of all sorts, servers, gaming, nice useable desktops and I always use OCZ psu's. Never ever have a problem with them and the cabling always fits fine. But that's just me. Built one last week with just the OCZ unit your link shows. I also run a 600w OCZ Xstream psu in a machine I built a year ago. Really quiet.

Edited 13 November, 201114 yr by Estate Man