Power Supply Unit (PSU) Basics
Power Supply Units frequently in the words of Rodney Dangerfield "get no respect". A solid power supply unit
with the proper wattage for your needs regulates power, and provides it in a stable and reliable form to all of
Gamers need to be on top of their power needs for the simple reason the the wrong PSU can cause an unstable
system, memory errors, data corruption, and it can also kill other components (collateral damage) when it
Sometimes, these errors are obvious and consistent making it easy to track down. Sometimes, they are subtle and
infrequent making it more challenging to pin point what the issue is.
Things to look at:
- Efficiency Rating: Most ratings are at 80% or higher. This is very important. What that means is the
extra 20% is wasted in the form of heat. Heat kills. Do not get a PSU with a less then 80% rating. There are
some that have 90% ratings, these are even better and of course more expensive. Within the ratings are
sub-ratings bronze, silver and gold.
- Form Factor: Check to see what your case is designed to hold. Mid-size and mini towers usually
accept ATX12V/IPS12V. Smaller cases tend to use SFX12V, TFX12V or worse a proprietary PSU. If you have a
Mini-ITX case, it's more then likely a Mini-ITX PSU you'll need.
- Manufacturer: Most vendors do not manufacture their own power supply units. Antec and PCP&C
purchase and re-brand theirs. Seasonic manufactures their own and sells them under their own brand as well as
selling them to other vendors for re-branding. If you're curious the info on the UL label can allow you to look
up the manufacturer online.
- Modular: Love them. Love them. Love them. Cannot say enough good about them. Cable management is
easier, as you only attach the cables you need for your current configuration. Extra cables stay in the bag
until required at a later date. These PSUs cost a bit more. Keep in mind that in theory because it has
jacks/plug instead of soldered the connections they are less reliable. Frankly, I've never had that issue.
I prefer the convenience of neater cables and better air flow I get with these PSUs.
- Berg: Obsolete. 4 pin connector was used to power floppy drives. Most power supply units no
longer include this connector. Most floppy drives are USB powered now. Adapters are available if you
are still in need of a Berg power connector.
- CPU: ATX12V is a 4-pin power connector, ATX12V and EPS12V have a 8-pin connector, optionally
they may have the 4-pin connector as well.
- Main Power: ATX12V 2.x = 24 pin, older motherboards use a 20 pin power connector (ATX12V
- Molex Power: Obsolete. Was used for ATA/IDE, now used for fans, maybe front panels or some
other internal peripherals.
- PCIe Power: 6 pin connectors supply up to 75W of extra power to a video card. 8 pin
connectors supply up to 150W extra power. The 8 pin is backwards compatible with a 6 pin video card.
The reverse is not true. A 6 pin power connector is NOT forward compatible with a 8 pin video card. An
8 pin video card needs more power then a 6 pin connector can supply.
- SATA Power: Has become the current standard in supplying power to peripherals, replacing
Berg and Molex connectors. There are 15 pin standard, 6 pin slimline, and a nine pin micro SATA power
connectors. Adapter cables are available if needed.
- Wattage: Unfortunately, these are not standardized. You can't compare PSU units of different brands
and assume that 700W is 700W. It is not. A solid PSU will specify their wattage ratings at 40°C or 50°C. Cheap
PSU units will rate at 20°C or 25°C. In real terms what that means is a cheap 500W unit's output at 20°C is
500W, but at higher temperatures it delivers only 300W. In the real world that cheap 500W PSU is grossly over
rated and will not ever deliver 500W under a real load.
- PC Power and Cooling
There are many good power supply brands out there. These three brands will get you started if you are unsure of
which brand to choose.Tips:
Know what form factor you need for your case before you shop
Be sure to calculate out your wattage needs with added wiggle room for future growth.
Lengths of SATA power connectors are important, as well as amount of them available. 2 generally is not
There are Wattage calculators available online.
Antec has one I really like.
You can choose to use a calculator or manually calculate your wattage needs. Either way, don't just guess. You
need to intelligently purchase your power supply unit, it will save you a major headache down the road.
Return for Power Supply Units to Home Page
PSU Install - Prep your case and install your PSU.
Power Supply More Tips