Which PSU should I buy, 650w/750w/850w Modular or 850w non-modular?

[richieuk]

I ordered a 650w PSU for my rig, but I've been looking at the PSU calculator, erring on the side of caution and leaving out a possible Crossfire upgrade in a year or so, I'm looking at 650w draw minimum, with 700w on 25% capacitor aging. Bearing in mind in comparison to my current rig, even on 50% aging it only just comes close the the 520w PSU I'm running it off.

My question therefor is this, do I pay the extra 25 or 30 pounds for a 750 or 850w Modular XFX PSU, or am I being silly and over-reacting? Is powerdraw a big issue?


Current Rig = Q660 G0, 2x2GB DDR2, 1 Sata2HDD, Fancontroller, 4850, 4 Fans, DVDRW, P5Q Pro mobo
All running off a 520HW Corsair Modular PSU.
New Rig = i7 2600K oc to 4.4, 4x4GB DDR3, 2 Sata3 HDD, 1 Sata3 SDD, 1 BluRay, 3 LED Fans, P8Z68Pro Mobo, Additional PCI-X Capture card, 6950 (unlocked to to 6970) *possible CF upgrade in the future if I need it or win it*
All running off whatever XFX Modular you choose.

http://extreme.outervision.com/psucalculatorlite.jsp


Options -

http://www.scan.co.uk/products/650w-...135mm-gray-fan (Currently ordered for £67 - 52a Rail)
http://www.scan.co.uk/products/750w-...-12v-135mm-fan (Pay an extra £22 for 62a rail)
http://www.scan.co.uk/products/850w-...35mm-quiet-fan (Pay an extra £28 for - 70a rail)
http://www.scan.co.uk/products/850w-...-12v-135mm-fan (Pay an extra £8 for - 70a rail)

What do you think?

[kalniel]

PSU calculator is usually miles out.

650W would more than cover a XF'd solution in the future. Your actual draw would probably be more like 350W, so in the sweet spot for efficiency.

[richieuk]

If I buy the 850w non-modular PSU, will it do the following.

Be easy to tidy wires in a BitFenix Survivor case?
Draw the same amount of power as the 650w, but allow for a higher powerdraw in the future when I upgrade - Or will it by standard draw an extra 30% power?
Be able to run crossfire 6970s as and when I upgrade?

[kalniel]

Echo.. echo.. ?

You need to check the efficiency curves. An 850W doesn't inherently draw more than a 650W at the same loading.. except that at very low loading PSUs aren't as efficient. So for a realistic loading both normal and CF the 650W is likely to be more efficient, because you're probably only going to draw 350W max.

[dfour]

So, what kind of power supplies would we recommend. Well, considering these tests put full load on the graphics card with very little load on the rest of the system we would recommend a quality 700W or higher power supply for a HD4870 Crossfire system and a 600W or higher PSU for a HD4850 Crossfire setup.

There test show a power draw of 376 watts with 4850 XF

http://www.hardwarecanucks.com/forum...review-15.html

[richieuk]

There test show a power draw of 376 watts with 4850 XF

http://www.hardwarecanucks.com/forum...review-15.html

I'm looking at the equivalent for a 6950 though, with i7, 4 sticks of ram, 3 Sata drives and an additional PCI-Express slot in use.

[richieuk]

Your actual draw would probably be more like 350W, so in the sweet spot for efficiency.

Draw of a XF 6950 is in a test bed over 500w, so even with additional Express lanes and Satas in use this will not spike out of realistic efficient-nezz then? I just got hella worried cause I looked at the PSU calculator and it was quoting a nigh 1000w PSU if I plan to use for 2+ years.

[shaithis]

I recently had a seasonic 700w PSU retired after over 6 years (the 3.3v rail is almost zero now).

During that time it always had a high-end multi-GPU setup to run, as well as a ton of drives, pump, raid controller, sound card, pump, fans, lights etc.

The worst loads on it were a 4870x2 + 8800GTX....handled it all without a problem.

Those calculators are normally way OTT.

[richieuk]

I recently had a seasonic 700w PSU retired after over 6 years (the 3.3v rail is almost zero now).

During that time it always had a high-end multi-GPU setup to run, as well as a ton of drives, pump, raid controller, sound card, pump, fans, lights etc.

The worst loads on it were a 4870x2 + 8800GTX....handled it all without a problem.

Those calculators are normally way OTT.

Theres the reassurance I needed This is a Seasonic IIRC (XFX just label it)

[Pob255]

Power use of a i7 2600k (+ 5850) at different overclocks
under cpu stress testing
http://www.tomshardware.com/reviews/...cy,2850-9.html

GPU 6950 unlock to 6970 effects
http://www.techpowerup.com/articles/...ng/vidcard/159

5850 idle is roughly 18w
6950 load is roughly 169w

so
i7 @4ghz = 191 - (5850 idle) 18 + 169 (6950 load) = 342w
unlock 6950 to 6970 +33 = 375w

Power consumption on crossfire, harder but looking at this
http://www.legitreviews.com/article/1488/18/
You're looking at about +40w for an over clock to 4ghz so about 550w in total (based on 2x6970+4ghzOC)
Add a bit of additional head room, I'd say 650w minimum. 750w-850w ideal

PS on capacitor aging, good cap's should lose no more than 50% over their life cycle (the life cycle of a cap is in active hours) the Cap's regulate the power (filtering and stability) so that doesn't mean 50% cap will reduce the current by 50%