Dual power supply or single

[diven nuttall]

Hi i was wondering if i should use one power supply or two for this computer.
specs:
ram: 8gb ddr2
cpu: core 2 quad Q9550
gpu: hd 5770
HDD: 2tb seagate drive
i have 2 power supply one 240w and one 365w, i was wondering if i should connect the two together or just use the one 365w psu. btw 26A on 12v rail and for the 240w 18A.

 

[Darkbreeze]

It really doesn't work that way. Unless you had two GPU cards, and each power supply supported the necessary amperage on its rail to support each card, there would be no benefit. Even then, it would be a backwoods remedy. Neither of those power supplies has the required capacity for the 5770, which calls for 450w minimum and 40A on the +12v rail. Plus, since you don't list the brand or model number for either units I have to assume they are either OEM units, are cheap off brands or are no name unlisted versions, which makes it even worse in any of those scenarios since those kinds of units rarely are able to achieve their rated capacity. I'd suggest getting a single high quality PSU with around 500w. Tier 1 or 2 would be recommended. Tier 3 would work in a pinch.

http://www.guru3d.com/articles-pages/radeon-hd-5770-review,11.html

http://www.realhardtechx.com/index_archivos/Page362.htm


PSU Tier list: http://www.tomshardware.co.uk/forum/id-2547993/psu-tier-list.html#15349669

 

[diven nuttall]

wait you know that the 40A is the whole system right. the graphics card ownly take 8A. and yes they are both oem hp dc7600 and hp dc 7900 psu. iv had the system running on the 365w one and it ran fine.

So what im pretty much asking is i have no money to spend so you would say i should just leave it as is or add a 240w psu to run the gpu it has double the 12v amps than what the gpu requires (16).

 

[Darkbreeze]

Of course I know what components use. I've been building systems for over 25 years my friend.

Single GPU 5770
•System in IDLE = 228 Watts
•System with GPU in FULL Stress = 321 Watts


Add 100w to that for overhead, or else you'd be running at what the max capacity of the unit is which you don't want to do, and you've got 421w, which rounded means you want at least a 450w unit. The power supply should never be run continuously beyond 80% of it's capability or you'll significantly shorten it's life and put your hardware at risk of damage if the PSU decided it's had enough.

450w times 80% is 360w, which is close enough to 321w for our calculations. And all of that is assuming a GOOD unit that's capable of sustaining it's listed capacity. Most are not. OEM and off brand units almost never are.

 

[diven nuttall]

so i should just use the 240w psu to power the gpu and the 365 to power the rest of the system

 

[Darkbreeze]

I'd do it the other way around, if at all. The GPU will use way more power. Most systems, not counting the GPU, don't use more than 100-150w total unless there's overclocking going on or a very high TDP chip is being used.

 

[Darkbreeze]

I'm not even sure it's feasible to do it that way honestly. http://www.tomshardware.com/forum/298250-28-identical-power-supplies

 

[diven nuttall]

if i have a psu with 2 10A 12v rails can i join them together to make 1 20A rail to run a power hungry component.

 

[diven nuttall]

http://www.ebay.com.au/itm/HPS-680W-PC-Power-Supply-Quiet-ATX-Computer-Gaming-PSU-/250768538601?pt=LH_DefaultDomain_15&hash=item3a62f83be9 would that work as a psu for me?

 

[Darkbreeze]

I wouldn't buy that. It's an unknown off brand and is pretty much guaranteed to be extremely low quality. I'd stick to units listed at Tiers 1-3 on the Tier list I posted above. For the most part, if it's a quality unit that's been reviewed, anywhere in the world, it's either on that list or has a similar model using the same internal platform as one of those listed there, and that one is not one of those.

 

[diven nuttall]

ok im going to get a cosair cx 600 psu.

 

[Darkbreeze]

That's not the best model in the world, but it's MUCH better than ANY of the others listed here. It should be fine.