Information on the Nomenclature, Terminology, Specifications, and Notes used for our Computer Power Supplies
Definitions of power supply terms used:
- PSU - Power supply unit ;-)
- OVP - Over voltage protection
- OCP - Over current protection
- UVP - Under voltage protection
- OLP - Over-load protection (AKA OPP, over power protection)
- OTP - Over temperature/thermal protection
- SCP - Short-circuit protection
- PFC - Active or passive Power Factor Correction
Where we mention something about "actual power" and what the specs actually show: Most PSU's are overrated with their wattage and/or amperage figures (amps is the current given in the "A" letters and is from what the wattage is calculated). These figures are usually PEAK MAXIMUM values and not continuous. We mention the actual wattage figures calculated from the amps where applicable just FYI. Most of the more expensive high-end PSU's are UNDERrated.
In the case of dual 12V rail or multi rail PSU's; the 12v current ratings are NOT combinable. For instance, if you have 12v1 & 12v2 @15A each, the total 12v current is NOT 30A (360 watts), it would be something like 20-23A or so. The manufacturers usually DO NOT mention this! There are some rare PSU's on the market that do indeed have actual combined 12V rails via either a manual switch, or their internal make-up that allows this. While the 12V rails are not numerically combinable, one rail can sort of "borrow" from the other should the need arise.
According to PSU manufacturers, dual or multi 12V rails are supposed to be more stable because one of the rails may be dedicated to: the motherboard's square 4-pin 12V CPU power connector, and/or main ATX motherboard power connector, and/or PCI-Express power connector(s); and the rest to the peripheral Molex type devices. This breakdown of 12v rail distribution varies from manufacturer to manufacturer, and PSU to PSU.
Regarding the main 20-pin Vs 24-pin PSU to motherboard connectors: Any 20-pin PSU WILL WORK with a motherboard with 24-pin power connector, assuming of course it has the power/current requirement to power the motherboard and components. Most 24-pin motherboards have a 4-pin "knock-out" plug which is usually in place for 20-pin PSU use, and this plug of course can be removed when a 24-pin PSU is used. In the event a motherboard does not have the capability to work with a 20-pin connector, an adapter can also be used for this which enables a 20-pin ATX PSU to be used with a 24-pin motherboard. These extra 4 wires are for 3.3v, 5v, 12v, and Ground, and since a 20-pin ATX PSU already has these voltages at the 20-pin connector, the 3.3v, 5v, 12v, and Ground are simply routed off from these lines to the 4 pins at the 24-pin side.
A "20+4 pin" PSU can be used with a motherboard with the 20-pin power connector. "20+4 pin" means a PSU has a 24-pin connector with this extra 4-pin area detachable for 20-pin motherboard use. A 24-pin ONLY PSU usually cannot be used with a 20-pin motherboard, unless; that specific side/edge of the ATX connector on the motherboard where the extra 4 pins would normally go has clearance enough for the "overhang", and the thickness of plastic on the PSU connector and motherboard connector is thin enough to facilitate full and proper seating of the connection (which is almost always the case since this thickness dimension is pretty universal). See this image for an example of how it can work.
All of our 20-pin PSU's have the option below their description to order with the 20-pin to 24-pin adapter.
Most of the newest 24-pin or 20+4 pin PSU's DO NOT HAVE a -5v rail. This rail was abolished since it was used for motherboards' ISA slots which have not been made for a while now. Therefore if your motherboard has ISA card slots, and you ARE USING ONE OF THEM, you CANNOT use a PSU that has no -5v rail! They may not even work even if you are not using any of the ISA slots.
For PSU's that don't have enough of the large 4-pin Molex type connectors, it's Ok to use "Y" adapters for fans, bay devices and the like as long as you don't over do it. These are also Ok for HD's and optical drives as long as there are is not more than 1 adapter per cable. If you need one of these with a PSU that you believe does not have enough, just state so in the notes/memo area when ordering and we'll include one free.
Do not be concerned if a PSU does not have PCI-Express power connectors. Most if not all retail boxed PCI-Express video cards come with a 4-pin Molex to PCI-Ex power cable adapter (if they don't, they are cheap to buy one) and these are used to convert a 4-pin Molex cable to a 6-pin PCI-Ex cable. The 5v line on the 4-pin connectors is simply not used on a PCI-Ex cable (just 12v and Ground is used). What you DO need to be aware of is the recommended current on a 12v line for your PCI-Ex video card. (Split-multi 12V rail PSU's not withstanding), some PCI-Ex cards require as much as a TOTAL of 26A on the 12v line of a PSU (nVidia 7800GT for one example). In the case with dual 12V rail PSU's, the 12V load is split/divided between the multiple rails and 15A on each 12V rail is usually enough for the vast majority of PCI-Ex video cards, even if TWO are used in SLI or Crossfire configurations. If in doubt whether any of our PSU's will work with your PCI-Ex video card, just ask the card's manufacturer about its current (amps) requirement, or you can ask us.
Do not be concerned about any lack of SATA power connectors on a PSU. As with PCI-Ex video cards, most if not all retail boxed SATA HD's come with 4-pin Molex to SATA power cable, and most SATA HD's also have the integrated conventional 4-pin HD power connector in addition to the SATA power connector. Additionally, most if not all retail boxed motherboards with SATA controllers also come with the SATA-to-Molex power adapter.
If you happen to need a 4-pin Molex to PCI-Ex power cable adapter, or, an SATA to 4-pin Molex adapter with your PSU order from us where the PSU does NOT have them, just state so in the notes/memo area when ordering and we'll include one free, *IF* we have them in stock. Unlike the "Y" cable adapters, we do not normally keep these in stock so we cannot guarantee we can include one with the PSU. However if you do need one and we don't have them in stock, we can locate one for you (about 3 bucks or so).
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