Each card will take up around 100W max (OC allowed), so with a C2Q you can still get away with a 500W PSU (200W GPU +200W CPU + 50W rest of system). A 550-600W will be decent for a added safety margin.

In this case, its definitely the Tier 4. If you read the review by jonnyguru, you'll be damned scared to run that thing at anywhere near full load..
Heck, I'll put better store in a cheap Acbel..

To summarise it,

Active PFC is mainly useful if you use a UPS (better power factor means more battery time)

OR

If your house power supply is unstable (in which case, you should be getting a UPS, rather than relay on the PFC's ability to handle voltage fluctuations. Don't get Auto Voltage Regulators, if you consistently suffer from unstable power they're not that much help, they're meant to just be extra security for NORMAL power situations).

Treat the extra efficiency most APFC PSUs have as a bonus, but if you really want an efficient PSU you should be looking at its efficiency rating, not whether it has PFC or not.

AVR and surge block is ok for the occational surge, but they are just an extra layer if security "just in case something happens". Meaning they'll take the bullet which would have taken you PC down. However, if the main AC supply is unstable to start with, then it means there is a fault with power cabling or contacts, both of which can easily cause more severe problems than can be handled by AVRs. In this kind of situation where you definitely have a problem, AVRs and surge blocks are not adequate, especially when dealing with voltage sags and drops suge block DO NOT WORK AT ALL, and AVRs can only compensate for a limited amount of voltage drop, and for an extremely brief time only. Moreover, PSUs already have decent voltage compensation built in (even cap ayams, though quite pathetic, about +- 15V), APFC PSUs can even withstand voltage drops up till 90V or lower. Its unlikely that an AVR can significantly improve the situation considering the capabilities to PSUs today, however they do act as a sheild in event of a massive voltage fluctuation they'll fry 1st, rather than your precious PC.

I doubt that will happen, with energy efficiency being the main focus now, even ATI (which produced the ultimate power-guzzling 2900XT) is pushing for more and more energy efficient designs. The 3870X2 actually takes less power than the 2900XT, for a start, and outperforms it noticably in games that utilise both cores properly. For processors, energy efficiency is everything now, the 45nm Core 2 Quad takes less power than most 65nm Core 2 Duos, and power consumption doesn't rise that much even under overclocking.

It IS true power.

Read this
http://www.jonnyguru.com/PSU/eXtremePower430W/

If you go around reading other proper PSU reviews done with voltmeters and stress loaders, you'll realise its actually better than most of the PSUs of the same price. Voltage regulation is pretty good, and ripple voltage is kept to a minimum.

I'm not sure about eview, but I'll withhold judgement till I can actually test one. But you're wrong about the CM extreme power 390-460W, though it would be true for the higher wattage models (500W and above). Read the article below

http://www.jonnyguru.com/PSU/eXtremePower600W/ (Make sure you read the above article on the 430W model as well).

I've never torture loaded an iCute, but the components inside leave me worried..its not what you'll expect from a >400W PSU. I've seen 200W PSUs a lot better built than those 400W iCutes. Have a look at the PSU I modded more than a year ago. Its a 170W Fortron aka FSP.

http://forum.lowyat.net/index.php?showtopi...255&hl=cap+ayam

Hmm, link is broken. Last time I visited it it was still ok, though that was months ago.

Ok, in short
-CM extreme power 430W was tested using a load tester by jonnyguru, loaded to almost 430W. All voltages ok, 12v line was about 11.8V if I recall correctly, rest we're within 2% of target value. Not much difference even in hot box test (where the heat produced from the power consumed is fed back into the PSU to simulate an actual PC's running condition)
-when jonnyguru examined the CM extreme power 600W, it was found to be using the circuit from a 460W PSU (forgot which maker), but when he asked CM, they said they modified the circuit to get 600W. However, the 12V line dropped below the 5% limit (11.4V) around 500W, therefore further testing was aborted as its a sign the PSU is beyond its limit. An additional sign was that efficiency & power factor dropped noticably at that point.
-all tests were done with the PSU loaded continuouslt for 1 hour

Even a proper 300W PSU is enough. I have set up a system for my friend, E2140 (overclocked to 3.0Ghz), 9600GT and a Delta 300W PSU. Everything is ok, checked voltages with digital multimeter. Voltages are hardly perfect, but still well within safe limits. Honestly, from what I know, the rig probably takes up no more than 220W.

That's an understatement. The ripple voltage on the Mushkin was so bad, to date I've never seen any PSU even HALF that bad (including the cap ayam PSUs which jonnyguru reviewed (and killed, I might add)).

Depends heavily on your system. The motherboard capacitors help to filter things out a bit, and most components now have some degree of filtering built in.

That would be quite right, which IMHO makes the mushkin a poor choice considering its easy to get a much better PSU for the same amount of money.

I'm not quite sure if looks are worth the risk, but its your money..how you want to spend it is up to you..

It depends..you can say its a sign that the manufacturer didn't pay enough attention to detail, with proper testing the problem would have been isolated and solved way before manufacturing, and with that kind of attitude you might not expect much from that kind of manufacturer. On the other hand, it may have just been not cost effective or too complicated to solve with a simple solution, so they may have just let it be.

For example, many Acbel(which also builds Cooler Master's PSUs) suffer from this problem, but as far as reliablilty goes I haven't seen any blow up, the only failures are some of the CM extreme power models above 460W which do no deliver their promised wattage without voltage regulation dropping out. In the case of the buzzing PSUs, Acbel probably didn't find it worthwhile to solve the problem either due to excessive cost, or excessing complexity (which often creates other problems), and this matches their style of making cheap, but reliable PSUs, though far from being the best around.

That would be nice if it was practical for everyone, but big casings in themselves can be a problem due to their size (lotsa wasted space). And also, like others here said even the size alone may not be enough as a solution. But up to you what you like

FSP is one of the 5 kings of desktop PSU makers a decade back before most of the other brands came about. They were PCP&C, Seasonic, FSP/Fortron and if I'm not mistaken the other 2 were Zippy and Tagan. The first 3 are still around, and still make the best PSUs money can buy, though they're each best in certain areas. PCP&C has the best in terms of raw wattage and voltage & ripple regulation. Seasonic has the highest efficiency of the 3 (being one of the first companies to achieve >85% efficiency). FSP makes the most affordable of the lot, without skimping on reliability, though their offerings tend to be towards the lower wattage range (<800W) due to their customer base being mostly OEMS.

1000W+ PSUs are not likely to become mainstream, considering increasing energy prices and the push towards highly efficient PC hardware.

It works like this, PC power supplies rectify AC power to DC then step it down & regulate the DC supply to the standard voltages used by PC components (12V, 5v, 3.3V, -12V). However, these are obviously not voltages you tweak during overclocking, the motherboard's voltage regulators are the ones responsible for the vDimm and vCore. Hence what you really need to pay attention to is the motherboard's voltage regulators.


Having said that, it is still important to get a good power supply because

-overclocked systems take up comparatively lots of power compared to non-overclocked systems (though still less than most people think), putting heavier stress on the PSU, often causing voltage regulation to suffer
-the power demand for OC-ed systems fluctuates more between idle and load (idle demand goes up slightly, while load demand skyrockets)
-all that shit must also pass though the motherboard voltage regulators before getting to your beloved processor, ram, GPU & chipset, putting their voltage regulators under immense stress. Having to cope with a fluctuating incoming supply on top of that can often be too much for regulator circuits to handle, though this depends heavily on the quality of circuit design & filtering on the motherboard. If its just too much, the regulator circuit will just blow, and possibly take out the rest of your hardware with it

Hence, get a good PSU if you're overclocking. Your hardware will thank you for it.




PS: For very special cases (world record overclocking under subzero cooling), the PSU DOES make a difference. That's because under those circumstances, a mere 0.005v fluctuation can spell the difference between getting another 50MHz more and taking first place, or blowing it. And with the insane voltage involved (>>1.8v for vCore), increasing it to compensate may not be an option for various reasons.