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PSU choice

Last response: in Components
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August 3, 2012 1:19:28 PM

Hi all,

I am trying to finalise my PSU choice, I have carried out a PSU calculation using the Coolermaster online calculator, it suggests I need a minimum 700W power supply. See result below:
https://dl.dropbox.com/u/47274064/IMG_1307.PNG
PLEAE NOTE: This is based on a Xeon processor as I may be getting this instead of an i5, for better performance on my analysis work. Also this is based on MAX set up of the system which I think I will end up with over the next few years.

To try and keep build costs low I have thought about getting either

OCZ 700W Modxstream PSU
http://www.ocztechnology.com/ocz-500...er-supply.html
REVIEW: http://www.hardwaresecrets.com/artic...y-Review/936/9

OR
OCZ ZS 750W PSU
http://www.ocztechnology.com/ocz-zs-...er-supply.html
REVIEW:http://www.jonnyguru.com/modules.php...tory4&reid=248

Here is the supplier comparison chart
http://www.ocztechnology.com/support...pply-selector/

I am in the UK, both are around £65.

I am not too worried if it is modular or not, my case has a big compartment to hide excess cables and my case does not have a window. I want to go for which ever power supply is the better one.

I have two questions
1) For the money am I getting the “best bang for my buck”? Or could I do better?
2) Which of the two OCZ PSU’s above would be the better choice, not taking into account the modularity of the modxstream?

I would really appreciate you input, please thank you.

More about : psu choice

a c 87 ) Power supply
August 3, 2012 4:01:05 PM

I seriously doubt that the MXSP700W would be able to support a build with two 7970s.
This is because it only has 552W available on it's +12V rails; the majority of the 694W number given by CM's calc is going to need to be deliverable on the +12V rail.
Secondly, it doesn't have enough PCIe connectors (only two, you need four).
Thirdly, the +12V rail arrangement is pretty crap on that unit, especially if you want to try to use molex to PCIe converters. They are all on +12V2, which is only rated to 25A, which is 300W.

So the OCZ ZS Series 750W is definitely the better choice because it has a higher capacity +12V rail (54A / 648W), it has the necessary connectors, it uses a more modern and efficient design. As you can see your potential build would still overload the ZS Series 750W unit, so I think you need to spend more to get a high quality 750W (with most of it's output capacity on the +12V rail).

These are two of the cheapest, high quality, 'proper' 750W PSUs that I know of:
Antec Truepower New TP-750 (£70 @ Scan)
http://skinflint.co.uk/407704

XFX ProSeries 750W Core Edition (£74 @ Amazon)
http://skinflint.co.uk/576814
August 3, 2012 4:41:23 PM

Do you think that the calculator is over estimating the power supply requirement? It does seem that some graphics card can take up to 175W of power each!

Thanks for your advice on the ZS vs ModXstream, that makes sense when you explain it the way you did.

Also, thanks for you suggestions on other power supplies. I hope I can fit something like that into my budget if I need to go for a 750W+ PSU :??: 
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a c 87 ) Power supply
August 3, 2012 6:14:43 PM

I do think that 694W is an overestimation for the power consumption of your system, but 750W is definitely a good size of power supply for a system with two 7970s.
The original 7970 has a maximum TDP of 250W.

Yes the PSUs I suggested are definitely better than the CM GX 750W. Here are some reviews for the GX 750 which definitely paint it in a bad light:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...
http://www.hardwaresecrets.com/article/917
http://www.xbitlabs.com/articles/cases/display/psu-550w...
!