psu for 4870x2 2GB DDR

[grepmonkey]

Hi,

I have a powercolor 4870x2 2GB DDR. I think I need a newer psu, but I dont know if I can just use a pci adapter for the 8pin, as I already have a spare 6 pin molex on the existing psu.

Set up;
2.13 gigahertz Intel Core 2 Duo
4gb Ram
dvd

eXtreme Power Supply Calculator Lite v2.5 gives me these figures ;
Minimum PSU Wattage: 568 W
Recommended: 618w

but it gives the warning;
The recommended total Power Supply Wattage gives you a general idea on what to look for BUT it is NOT a crucial factor in power supply selection! Total Amperage Available on the +12V Rail(s) is the most important, followed by the +5V amperage and then the +3.3V amperage.

I dont understand what this means, the figures on the existing psu are;
+3.3 +3.5 +12v1 +12v2 -12v +5vsb
30A 38A 18A 17A 0.3A 2A


+5v& +3.3v combined 185w total 550w


Im assuming ill need a new psu - is that correct?

Cheers

[kalniel]

Yes, probably.

The figures that are most important are the +12v ones - you need to allow about 20A per rail and ~30A combined exclusively for the graphics card. The combined figure is important because sometimes the rails will say they can supply 26A each or whatever, but that could be peak and unsustainable across several rails - there will be a box where you can work it out (remember Watts = Amps x Volts)

[Pob255]

Umm you'll find 18a per 12v rail is ATX spec, well per solder point on the PCB which is how rails are normally divided up in a PSU.

First thing to ask is what make and model is your psu? that'll give us a better idea as to how reliable the numbers are.

Here's some base info
a 8pin pci-e connector is rated for 175w max or ~14.5a
a 6pin pci-e connector is rated at 75w+ (over just two of the +12v pins, yellow leads*) or 6.25a
a pci-e slot is rated at 75w max or 6.25a
*6pin pci-e is not actually an open spec so info is sketchy, the 2xmolex to pci-e adaptors that come with graphics card generally use only have 2 positive pins (yellow leads) and are rated for 75watts, so a full 6pin pci-e connector should be higher rated however that would make it incompatible with adaptors.
Most psu's & graphics card work by shareing the load over the 3 wires, to share the load and strain, thus reducing overall fluctuation and noise.

The 4870x2 uses around 262w under full load or ~22a (and about 7.5a idle) some of it coming from the motherboard and some from the pci-e connectors.

So under load that could be too much for your psu, a lot will come down to how good the psu is, how accurate the numbers are and how the rails are divided.

Just off the numbers you've given us, I'd edge on the side of caution and say No.
I'd look at something around 500w which has the correct number of connectors to start with.
eg http://www.scan.co.uk/Products/500w-...2V-6Serial-ATA (that model is actually made by seasonic btw)

[grepmonkey]

Ok thanks.
So im assuming that the;
1 x 6+2pin PCI-E Power goes in the pin slot?

If thats the case thanks, that psu looks to fit the bill.

[Pob255]

The 4870x2 should have a 6pin socket and a 8pin socket
the 6pin plug on the psu goes in the 6pin socket and the 6+2pin one goes in the 8pin socket.
Basically the 2 extra pins are detachable so it can be used in a 8pin or 6pin socket.

Actually before you go off and buy that psu, I'm not so sure about it, quick double check.

[grepmonkey]

This looks like it would fit the bill;
http://www.scan.co.uk/Products/530W-...n5xSata4xMolex

what do you think?

[Pob255]

Yes it is the seasonic made model, however I cannot find a good review of it, there's a couple that tested it with a quad core and 4870x2 it worked but the 12v was starting to drop, still in atx spec but not as close as I'd prefur, but at the same time I don't trust a review that cannot tell the difference between an 8pin EPS motherboard connector and an 8pin pci-e connector, ok at first glance they look the same, but look at the pins and they are different and you cannot plug them into the other type of socket.
and if a reviewier cannot spot that fact I'm not sure I'd go far in trusting the rest of the results.

You should be fine as you're on a lower wattage cpu.

Here are some others to consider
http://www.scan.co.uk/Products/550W-...-Year-Warranty (44a single rail 12v)
http://www.scan.co.uk/Products/560W-...2x-201-EPS-12v (20a+20a 12v)
http://www.scan.co.uk/Products/520W-...0TX12V-V23-PSU (40a combined rail 12v)
http://www.scan.co.uk/Products/530W-...n5xSata4xMolex (22a+22a 12v but not in stock atm)

edit:@grepmonkey yep on my list but not instock