Tec-heads needed - PSU 12v/amp question

Hi, I hope some of you can help me. I currently have this 380W psu http://www.coolermaster-europe.com/index.php?LT=uk&Language_s=15&url_place=product&p_serial=RS-380-PCAP&other_title=+RS-380-PCAP+eXtreme%20Power%20380W

heres the stats:



I need to know if my PSU can support this gfx card http://www.bfgtech.com/7600GT_256_PCIX.html which stats I need a 350W PSU with 12V current rating of 20A or more.

My Wattage is ok but I am a little confused as to what AMP my PSU is as there are 2x12v values, do I add these up? or? what is the max 12v amp on my PSU?

Thanks.

I've run a 7800GT on a 400W supply before without issue, with tons of other hard disks / PCI cards in the box too. Coolermaster should be a solid brand name and reliable - if you want to be absolutely certain try asking on:

http://forums.overclockers.co.uk

under their PSU section.

your max amp on 12V is 15A.

I think it will work- between the two 12V outputs you can source 25A. I'm assuming the GFX card doesn't require a single 20A supply for its exclusive use.

What Lars said. You don't have enough amps to power the graphics card.

Thank for the answer guys, ive posted on several other forums too, no replys yet.

But im sure you add up the the 2 +12v rails like Nomen said, even the top spec PSU from coolermaster which is designed for top end SLI systems only has 18amps on each of its 6 +12v rails http://www.coolermaster-europe.com/index.php?LT=uk&Language_s=15&url_place=product&p_serial=RS-850-EMBA&other_title=+RS-850-EMBA+Real%20Power%20Pro%20850W

So apparently this PSU which costs $250 cant even run 1 7600GT (a medium spec cards) I find hard to believe, as it can run duel 8800gtx (highest spec card out).

None of the coolermaster PSU's have more than 18amps on a single +12v rail.

I can't see how you're wrong, coffee. The two 12V outputs, both at their max current, tots up to the 300W stated for them. If they can't both output at near max current simultaneously, then the supply can't deliver the 380W it claims, according to the other numbers.

The requirement for using twin cards is only another 8A, suggesting the gfx card pulls only about 8A. So the question is can you spare 8A (say 12 to build in some safety) on one of your 12V supplies?

I got a reply from some 1 on tomshardware.com



So Im sure I have a total of 25amp to play with so I should be ok. Plus I have not been able to find any PSU with more than 18amps on 1 +12v rail.

The appears to be a little ambiguity between what the PSU says it can supply and the reply you got from tomshardware.

Yes the total 12V capacity is 25A but if both 12V supplies were combined then why list them separately?

If they are not combined then you can only draw 10A off of one and 15A off of the other, you won't be able to supply the card with 20A off of one 12V rail and since the PSU appears to indicate that the supplies are not combined electrically then you cannot draw the 20A required of off either one of them.

That said, from your investigations you come to the conclusion that there is no PSU out there that meets your requirements and this strikes me as odd, and that the tomshardware reply may well be right and your PSU is wrong in saying that the 12V rails are separate.

I suppose the only way to really find out is to either get a schematic of the PSU...from that I could tell if the two 12V rails are separate...or to just plug the card in and see for yourself ;)

[Edit] Based on the PSU labelling and the requirement of the graphics card of 20A then no, you won't be able to supply enough current since you can only plug the card into one of the 12V rails, not both at the same time.
I would ask the manufacturer what PSU they recommend and do you really need to supply 20A?

Well the Tomshardware guys basicly said the psu has 2 +12v at 10amp and 15amp because its safer to spread the amp across 2 rails rather than push it through 1 rail.

What hes saying and what ive garnered from scouring the web for the last 3 hours is that all parts of the system use the amp, the hardrive needs an amp or 2 the CPU will need a good chuck also, so with a 2 rails 1 rail goes exclusivly to your CPU and the other to power the other parts.
The gfx card does not needs 20amps to its self, but needs a system that can deliver at least 20 amp across the whole system and will take a what amps it needs from that total.

There are single rail PSU with 20-25amps on a 12v, but all duel rail PSU seem to draw the line at 18amps.

So i guess the 10amp rail goes to my CPU and 15amp rail goes to gfx card and other parts and that rail is fine becuase none of its amps are going to power the CPU.

I'll dig around soem more but im 90% sure of the whole amp thing. And I learned somthing I new.

The reply from TH is a little misleading. The 10 amp rail is more than likely the P4 style connector. The P4 Northwood uses about 8 of those amps, and newer CPUs will use more, so saying that you have 25 amps to play with is at best, downright wrong. You have at best, 15 (assuming that the P4 rail also powers the PCI ports). If I remember correctly each PCI port can pull about an amp each, and one of these are probably being used by the gfx card. So depending on the number of other peripherals you have hooked up to the machine, you have in a best case scenario (one HD, one CD/DVD drive) 13 amps left over. Now if the 15 amp rail is the one that'll give you a PCI-E power connector, you'll have plenty of power to spare (providing the actual power drain for the gfx card is only 8 amps).

This might be the case as the manufacturer is probably American and has product liability issues to worry about. My graphics card for instance required "at least a 350W PSU" - obviously tallied into this number was power requirements for the other system components (it actually needs 420Watt when assembled).

Of course if the order of the rails are the opposite of my assumptions and the 15 amp rail is the one that powers your P4 connector, you're in pretty big trouble.

Personally I think you're cutting it a little close - even if it does work initially the PSU is likely going to give up on you relatively quickly when being pushed so close to its operational envelope. I'd get a big PSU anyway, just to be sure.

Edit: Alternatively, get a PSU with 3 rails.

Cant realy afford a new CPU + GFX card =(

But I came across 2 sig's from ppl on different forums showing them using the same psu as me with a 7600gt gfx card, different makes but a 7600gt from 1 to another should not be more than an +/- 1amp.

Plus the XFX is overclocked just like the BFG.





I've send an email to BFG any way, to be sure.

you really should get a bigger PSU..
I'd recommend you get atleast a 500W, if you're going to use a "current hungry" graphics card..

I can almost guarantee that you'll eventually run into power supply problems with that power supply... and it can cause all sorts of wierd problems...

my 2 cents

I used to have a 480W PSU with 1x22amp 12v rail but that only lasted 6 months with a 6600, so im staying away from Watts and looking to amps from now on.

I just got a reply from BFG they said the power supply would be fine, got a reply from 1 of the guys with those forums sigs, the guy with XFX said hes run the card for over 7 months with no issues.

I have also emailed coolermaster to find out which 12v powers the cpu if its the 10amp an d leaves me the 15amp for the gfx and other parts then ill be pucker. =D

Watts=Volts*Amps so if you get more amps you get more watts anyway ;)

Sounds like BFG don't really think the card needs 20A (which is 240 Watts at 12 Volts), if they had told you the real power requirement for the card in the first place you wouldn't have to have made this thread.

Hope you have fun with the new card =)

You will be fine with that PS and video card. The dual rails are fine. I am running this one and it has 4 12V rails!

http://www.bfgtech.com/power_supply_800W.html