When buying parts to build a new system many people underestimate the importance of the power supply. We receive a lot of emails and Facebook questions from readers who are experiencing system stability issues, many of which we find out are related to poor power delivery.
When buying a power supply it is very important to work out exactly what you will need. A little forethought and planning will mean you won’t be spending extra money on a supply you don’t need, or one that won’t meet your demands or expectations.
For this review today we approached OCZ to send us a range of power supplies at various price points. These units are designed to cater to a wide audience. The budget models on test today are big sellers due to the very competitive pricing. Many OEM builders use these units. The high end models are designed for hard core gamers who are running multiple, expensive graphics cards in Crossfire or SLI configurations.
Before we get into the testing, we wanted to go over some points to help our readers when they are shopping for a new power supply. With such a wide range available online there have never been more choices available to the consumer. To the inexperienced user it can be confusing however. What should you be looking for?
If you have a system chassis with a window and are focusing on a tidy system build, then you will more than likely want to buy a modular power supply. There are several kinds of modular power supply available today. A ‘Pure’ modular power supply will have no hardwired cables. This means when you open the box and remove the power supply, there won’t be any dangling from the unit itself. A separate bag will be supplied, with every cable in it.
Other modular power supplies will have some cables hardwired into the chassis. These hardwired cables will often be the main motherboard connector, a couple of PCIe cables and the CPU 8/4 pin connector – these primary cables are often used all the time.
If you don’t get a modular power supply, then you will end up dealing with a plethora of cables you might not be using. All of these will need carefully routed out of sight behind the motherboard tray. Depending on the case you are using and the specific power supply, this can get messy.
Many computer cases don’t have a lot of space behind the motherboard tray, so you will need to get creative. If the cable routing is a key priority for you, we advise you opt for one of the modular supplies currently available online.
Don’t just blindly buy a power supply with a 1000W+ rating. Unless you are running an ultra high end system with two HD7990’s or four high end graphics cards you are highly unlikely to need one. Our recent review of the Sapphire HD7990 dual GPU graphics card running in a Quadfire configuration is a good example of just how much power you need.
The test system we used comprised a liquid cooled, overclocked Core i7 3960X with several hard drives, 16GB of 2,400mhz memory and two AMD HD7990’s running in Quad Crossfire. This is possibly one of the most powerful gaming systems you could build today and under load it demanded 825 watts. For this system we would recommend a 1000W or 1250W power supply, but what about if you are using a more modest configuration?
Many high gaming systems using an overclocked Core i5 3570k or Core i7 3770k with a GTX680 or HD7970 are likely to be requiring between 300-400 watts of power under load.
An example? Our recent review of the Cyberpower Infinity Fusion Titan SE featured information on system wide power demands. This gaming PC was built around a Core i5 3570k which was liquid cooled and overclocked to 4.6ghz. CyberPower also used the class leading £850 Nvidia GTX Titan graphics card. Was this another 800W power drain system? Not even close, this system demanded less than 330 watts under load.
Many people would think just because a system is using a high end graphics card that a 1000W power supply is needed. It isn’t.
A power supply will reach maximum efficiency between 40% and 60% of its maximum rated load. For the Cyberpower Infinity Fusion Titan SE system mentioned directly above, a quality power supply around 750W would be ideal, leaving a little headroom for adding in some additional hardware at a later date. Cyberpower decided to use the budget oriented Corsair CX600M (600W) which is close to 50% demand at load. Not a bad move really on their part but they were clearly trying to balance the monstrous cost of the GTX Titan to achieve the price point of £1999.99 inc vat.
Obviously this is only part of the procedure for buying the right power supply. You can also factor in the 80 Plus certification. This is the certification of rated efficiency. This will certify products that have more than 80% energy efficiency at 20%, 50% and 100% of rated load, and a power factor of 0.9 or greater at 100% load. That is, such PSUs will waste 20% or less electric energy as heat at the specified load levels, thus reducing electricity use and bills compared to less efficient PSUs.
We would always recommend at least 80 Plus Bronze certification for a budget power supply and when you spend more money, this certification will often increase to Silver, Gold and finally Platinum certification. Be aware that some power supplies don’t achieve their claimed efficiency levels. There have been many articles on this in the past and it certainly complicates the issue. Just because you see an 80 Plus Gold badge on the front of the box, it doesn’t mean the power supply actually has been certified.
That is an article for a different day however.
Ripple performance is also an important factor when deciding on a power supply, because if a specific unit falls outside industry tolerance specifications, it can be potentially dangerous. Ripple occurs with all SMPSU’s (switch mode power supply units). These are tiny fluctuations in a power supplies output voltage on the order of tens of millivolts, millions of times a second. Ripple is measured as a peak-to-peak value in milivolts and is measured using an oscilloscope.
The ATX specification sets these limits on computer PSU ripple levels (meaning we don’t want to see results in excess of these figures below):
+12V – 120mV
+5V – 50mV
+3.3V – 50mV
+5VSB – 50mV
Ideally (in my opinion) we want to see figures in this range:
+12V – 80mV
+5V – 35mV
+3.3V – 35mV
+5VSB – 50mV
A power supply which shows ripple outside (higher) than that listed by the ATX specifications can potentially cause hardware damage. There is no way of measuring when a problem might occur, but it is likely something will go wrong, long term. A power supply that shows good ripple suppression will help aid hardware longevity.
Ripple can have a negative impact on electrolytic capacitors. A ripple reading close to a capacitors rated ripple will potentially shorten the lifespan and ripple exceeding its rated level could cause it to blow. It is worth pointing out that electrolytic capacitors are found on a motherboard, a graphics card, the power supply and more – so the potential for damage is high. Using a power supply with good ripple suppression is very important. If you want to learn more about this, there are plenty of indepth technical articles available online.
Additionally, If you are trying to build a quiet system it is important to factor in the fan performance of the unit. A fan that has to work hard to maintain good internal ambient temperatures will likely produce a lot of noise which can be distracting, especially if the rest of your system has been built with silence in mind.
So let’s get on with the testing of these OCZ power supplies. We will be working our way up the power supply prices the further we get into this review and trying to explain what each power supply would be best suited to handling.