PSU: Power Supply University, Does Your PSU Make the Grade?
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So you’ve put the best motherboard you could find, the fastest hard drive’s on the market, the best DVD burner, a gig of ram, and the most powerful set of SLI video cards you could get your grubby hands on together with the biggest processor available to make your dream rig; now what? Well, now you need to install the thing that will make all these components work: the power supply unit (PSU).
The contemporary ATX-style PSU was introduced by Intel in 1995. With its standard 86 x 150 x 140 mm dimensions and 80 mm fan it’s become a consistently more important factor to PC design since its inception. Since 1995 it has continued to evolve and grow as the entire industry has while still retaining much of its original properties. The dimensions of the power supply unit have been altered to be both bigger and smaller by a variety of manufacturers. Specifically original equipment manufacturers (OEM) such as Dell, IBM, and E-machines have created proprietary PSU’s for their machines. Most of their mid-tower units still use the ATX-style power supply unit but many of their desktop-style chassis’s have used smaller and narrower units. The Dell Optiplex, for example, uses a power supply that is narrower and longer than its standard ATX counterparts. E-machines, on the other hand, have used smaller power supplies in their small form factor towers. These changes are often done, not because of any functionality increase, but for space considerations and for locking proprietary component replacements through their distribution channels. Regardless of any cutting or grinding or custom brackets, a standard ATX power supply would have significant difficulty physically fitting in these tight packages.
The main function of any PSU is to take your household electrical current from a standard wall outlet and convert it into power that your computer, or any home electronics, can use. The power supply takes AC (alternating current) from your wall outlet and converts it to DC (direct current) to power your devices. The computer power supply converts this DC power to the right voltages to provide each of your internal, and external, devices with sufficient power.
For example, a typical ATX power supply will have a +3.3V connector, a +5V connector, and a number of +12V connectors. The +3.3V and +5.5V connectors are designed to power internal circuits such as your motherboard. The +12V connectors, on the other hand, are meant for optical drives, disk drives, and hard disks as these devices require significantly more power to operate due to a number of factors including the presence of fast moving components that, obviously, need more power. The number of connectors has changed over time as the power supply unit has evolved, but the greatest change in power supplies has been massive jumps in wattage.
In 1995, when the present ATX standard emerged, the average power supply unit averaged a robust 250 watts. By today’s standards that’s rather minimal; but, in 1995, that was often more power than was needed to supply the average computer. Sadly, there are plenty of OEM proprietary systems still manufactured with measly 250 watt power supplies in them. However, the greater majority of power supplies starts at a minimum of 350 watts and can climb upwards to 600 watts of raw electrical muscle. However, the advertised wattage featured on packaging or as part of a power supplies name is not always true.
Next: Power Supply Efficiency >>
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