I've checked out countless forums about this but I can't seem to get a clear answer. I have recently bought a Thermaltake Purepower 480w PSU and it came with the old style 20pin Mother board connector. I know you can get 20 - 24 pin connectors but I've head that they're poorly made and won't make any difference. All I want to know is it safe to use this PSU? I know the extra 4 pins are for the PCI-e and since I have a Radeon 5670 plugged in then I'd imagine I need the extra power. I read that it may work depending on the Amps pushed out on certain rails.
For basic computer systems, yes. The evolution from 20 pin connectors to 24 pin connectors occurred when systems became more powerful. The extra 4 pins contain one extra wire for the three main power outputs - 12 volts, 5 volts, 3.3 volts, and a ground wire. Then they decided to power the CPU from its own 12 volt cable reducing the demand of both 5 volts and 12 volts from the motherboard. Memory changed from DDR (3.3 volts) to DDR2 (2.2 volts) reducing the need for 3.3 volt power. Then video cards started using PCIe power, further reducing the need for 5 volt power.
This power supply? Unless you are powering something with integrated video or a very low spec video card, the 12 volt rail is not heavy enough.
Specs of the system you want to power with this power supply?
The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the +12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the +12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5000 series cards which use less power due to their energy efficiency.
A high quality 500 to 550 watt psu will have a +12 volt rail rated at 40 amps. A high quality 700 to 750 watt psu will have a +12 volt rail rated at 60 amps.
In addition the power supply should be at least 80+ Bronze certified for energy efficiency. There are some models available which have achieved 80+ Silver and 80+ Gold Certifications.
Before purchasing a new psu you will need to decide whether you will eventually have a pc with one or two video cards.
Corsair and Seasonic are two of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units. One example would be the Antec Earthwatts series which is a major improvement over Antec’s older psu’s like the Basiq models.