Graphics card buying guide

When we refer to power supply requirements for a graphics card it is not simply a case of Wattage. There is a lot more to it than that, although Wattage is still important. Other things to consider are:

• Whether your power supply has the required connectors
• If your power supply rails contain enough amps
• (Total Wattage as mentioned earlier)
• Efficiency of your power supply

Your first core consideration when choosing a graphics card is: ‘can your system power it?’ If you already have a power supply then you have to work out how much in total your entire system consumes, you can do that here. Once you’ve worked that out, you should consider your power supply’s efficiency. For example an 80 PLUS power supply will mean you could lose only 5% of its maximum stated Wattage to heat waste whilst a really cheap 500W power supply may lose up to 30% of its maximum state Wattage because of its poor efficiency. (i.e the power supply may pull 500W at the wall but only deliver 400W to your system) Although if your power supply’s wattage is ‘continuous’ it should deliver its stated wattage irrelevant of its efficiency. With that in mind:

Power Supply Capacity – system power consumption = spare power capacity

Once you’ve worked that out its then a good idea to look at the graphics cards you want, find a review with power consumption figures and then determine if you’ve got enough power to meet the maximum potential draw of the graphics card. Give yourself about an extra 5-30% on what it says the graphics card consumes to make sure you account for the efficiency of your power supply.

The range of connectors is also important, for most graphics cards above the entry level of performance you may require any combination of 6 pin or 8 pin. Just in case you’re not sure and want to double check the 6 pin is shown below, and the 8 pin is shown below that.

With regards to Amps it’s really difficult to give an accurate estimate of what kind of numbers you need. As a general rule if your power supply is made to an 80 PLUS standard by a well respected manufacturer such as OCZ, Seasonic, Corsair or Thermaltake then you will have enough power on the rail(s) to power your cards providing the wattage is high enough and the power supply has the appropriate connectors. Remember the 6 pin provides a maximum of 75W, the 8 pin provides a maximum of 150W and the PCIe bus provides another 75W. This is just a general word of warning, as a lot of ‘lower quality’ power supplies will claim power delivery of say 600W but then the PCIe power connectors won’t be able to deliver enough power as they lack the required amps. You can also convert other power supply connectors such as the 4 pin molex into a 6 pin or convert two 6 pins in to one 8 pin. Sometimes this can be an issue (mainly for the molex to 6 pin coverters) as those molex connectors will tend to have less amps than a 6 pin connector should have as the molex connectors are intended to power hard drives not power hungry graphics cards.

Our advice is simple, you can either:

• estimate the power consumption of your system and work out how much you have available to you in terms of watts.
• go by the manufacturers recommendation for minimum power supply requirements.

Both those methods should give you a safe ballpark figure for how much power you can spare for a graphics card. Although it is worth noting that you can just upgrade your power supply when you upgrade your graphics card if this is easier for you. Power supplies are easier to change and more affordable to change than other components that can potentially be limiting like the processor which we will touch on in a bit.