New PSU for 6870 & future CF

[Toperharrier]

Well, Im getting a Saphire HD6870 (maybe a XFX one, not sure yet) and I know I want/need to change my old stock PSU (nt even PCI-e wires) for a good one. My actual rig is:

Q6600 G0 @3,3Ghz (1,35v)
Gigabyte P35-DS3L
Saphire/XFX HD6870 1GB
1x 7200 Sata HDD
1x Optical DVD drive
2x2Gb DDR2-800

Im planning on the possibility of a future 6870 CF, so.. Ive been told 500w would be more than enough (from a good brand/psu ofc) to power one 6870 alone. I guess Id need about 650w for a CF of 2x6870, am I right? or am I in need of even more horsepower to run CF?

Ive been looking around for a good one and Im sure Id like it to be modular, cos I hate useless wires around my rig so much (Im only using 1xSataHDD and 1xOptDrive atm)

Im buying from Europe, max budget is 80€. Ive been offered a Thermaltake Thoughtpower XT 875w for 80€ from a friend, but Im not really sure I need so much wattage nor Thermaltake or this specific PSU is any good at all (I heard some TT are real noisy, wich Id like to avoid!).

Any advice wld be much appreciated

 

[Rugger]

A single HD6870 requires a 500W psu with 32A on the 12V rails and (2) 6-pin 75W PCIe power connectors. Two HD6870s in CF require a 600W PSU with 44A on the 12V rails and (4) 6-pin 75W PCIe power connectors.

The Thermaltake Toughpower line of PSUs is a good line of PSUs and probably the only line I would consider buying from Thermaltake. Review: http://www.tweaktown.com/reviews/3736/thermaltake_toughpower_xt_875w_power_supply/index.html
That being said, that 875W PSU is way overkill for your rig with 72A on the 12V rail. Finding sufficient amps on the 12V rails won't be an issue, but the requirement for (4) 6-pin PCIe connectors will limit your options. Here are a couple:
1. XFX Pro 650W: http://www.scan.co.uk/products/650w-psu-xfx-pro-series-core-edition-p1-650s-ukb9-85-eff-80-plus-bronze-sli-crossfire-eps-12v-fan-at
2. beQuiet Efficient 600W; 80+ Gold: http://www.scan.co.uk/products/600w-psu-be-quiet-efficient-power-bn188-92-eff-80-plus-gold-sli-crossfire-eps-12v-fan-atx
Great bang for buck on this PSU with it's Gold certification. XFX is made by Seasonic and the BQT is made by FSP. With the BQT being less expensive and having the 80+ Gold cert I would go with it. The XFX is no slouch and is also a great option.

 

[Toperharrier]

How should I calculate the max wattage on 12v rail? The thermaltake crearly state only 1 12v rail (?) at 64,5A max. But the Bequiet has 4x 12v rails (?) 18A each, shall I sum them all? so Bequiet has a a max of 72A?

Anyways, would any of those PSU be a better choice than the Thermaltake? If its just a matter of overwattage in the Thermaltake its about the same price for me (80€ without shipment) than the Bequiet (64 pounds, abt 79€).

Shall I go with the Bequiet or would the Thermaltake be a better option? Bequiet is not modular btw

thx for your help

 

[Rugger]

You calculate the total amps available by dividing the max watt rating by 12V....or you can go to the mfr's website: http://www.be-quiet.net/be-quiet.net/index.php?StoryID=17&ProductID=239&websiteLang=en
It's 45A on the 12V rails.

If the cost is the same and you trust the person you're buying from then consider the Toughpower. It will be run at light loads....that should lead to quiet operation. If you consistently run it at really light loads, then you may waste a little money on electricity, but not a lot. I don't advise people to overspec like this because you can save money for other parts of the PC.