How to Choose the Best PC Power Supply – Guide

Of course, it’s what turns your PC on and keeps it running through all those spreadsheet marathons and fancy fragfests. But aside from the startup and shutdown time, your desktop’s power supply unit (PSU) doesn’t attract much attention. For most buyers, it’s seen as a generic component, a supporting player, compared to the glamorous PC silicon stars like the processor or graphics card. For an average PC tower that isn’t pushed to the limits of its hardware, this perception is a good one. Having a “good enough” PSU will suffice. But there are important differences between PC power supplies. And the more tied you are to extracting maximum performance from your PC, the more you should treat the PSU not as a checklist item, but as a component among equals. However, PSU shopping is loaded with its own language. This guide will present a brief summary of the jargon and basics of desktop power supplies here :updated and will present up to speed up what to look for.

What fits? Power Supply Form Factor Fundamentals

Power supplies, as we know them in desktop PCs, date back to the original IBM PC. But a brief history of current PSU designs actually starts a little later, in an era before the existence of the now familiar ATX form factor, for the IBM PC AT and PS/2 of the 1980s. -AT form factor motherboard with dual six-pin power connectors, and PS/2 form factor for power supply cases (not to mention a miniature keyboard connector). From there, Intel developed the AT Extended (ATX) motherboard form factor, which added more space around the processor and placed an extended port panel behind that space. With the last came a new 20-pin power connector that would support electronic switching. Power supply manufacturers responded by placing ATX PSU internals in their PS/2 form factor housings. Intel took over the standards organization and renamed the form factor “ATX”. This remains today, although there is some movement in the industry (specifically, spurred by Intel) towards a more recent 12VXO update to the ATX standard, the 12VXO update would simplify the PSU internals and only provide 12 volt power. (Current conventional power supplies provide 12 volt lines as well as legacy 3.3 volts and 5 volts.) The 12VXO is not yet a factor for buyers, but it connects to the duality of the ATX: beyond the actual sizes of the PSU, ATX chassis also remains a defining power standard. As for those sizes, though: the most common form factors today are PS/2 (better known as “full ATX”) and SFX, along with its derivatives. Full ATX is the full-size desktop power supply that most of us know well for upgrading or building PCs over the years. SFX, however, is a more modern development designed for smaller desktops. The original PS/2 form factor had a mounting plate measuring 150 mm wide by 86 mm high, a depth of 140 mm, and an optional two-slot support tab protruding from the front (with the power plug on the front). back). The original SFX specification, however, was 125mm by 63.5mm by 100mm, but many OEMs used a side-mounted variation measuring 100mm by 63.5mm by 125mm. Other (less common) form factors are described on pages 47 to 67 of the Intel Desktop Power Supply Design guide. Note that there is no “MicroATX” power supply form factor, although some vendors designate the SFX as such. Most MicroATX PC cases use full ATX or SFX mounting patterns for the PSU area, and other compact PC cases (like Mini-ITX models) that may use rarer sizes (like TFX or custom proprietary form factors) generally come with any such unusual type of power supply pre-installed. We mentioned the full ATX and SFX derivatives a few paragraphs ago. While the original PS / 2 form factor 150 mm by 86 mm mounting plate is common on full-size power supplies, most of today’s high-capacity full-featured ATX models exceed their specified mounting depth of 140 mm. Single SFX PSUs retain their nominal depth, but may also come in long versions. Power supply and case manufacturer SilverStone, for example, offer extended-length SFX power supplies under the “SFX-L” label, with an extra 30 mm space for their designers to specify a larger 120 mm fan and more internal hardware components. These extended-length PSUs invade the space normally reserved for cables, but many modern PC cases have some space to spare. Therefore, key point number one is to match the type of PSU (full ATX versus SFX versus SFX-L) to the PC case you have or are considering. Point two, you should look at the depth of any PSU you are considering purchasing and look at your PC’s case spec sheet to make sure the PSU’s depth measurement is below the limit. (In addition, many PC case reviews will describe the extent to which a power supply can interfere before it locks out.) Also be aware that some pre-built desktop systems from major OEMs (notably Dell and HP), as well as some highly compact desktops, may use proprietary PSUs that can only be replaced by the same specific proprietary models, usually provided by the OEM itself. A red flag is a non-standard main power connector for the motherboard that doesn’t match the 24-pin standard (more on this soon). If in doubt, contact your PC manufacturer’s support line or online chat to discuss the details of your specific system.

Do you have good connections? Knowing PSU cables

The individual cables coming out of a PC power supply are often called “conductors”. Intel’s original ATX power specification only required a 20-pin motherboard connector, later adding a separate square four-pin “P4” connector to provide a 12-volt cable to independently power the CPU. (This latest development showed up in the specification update called “ATX12V.”) The later EPS12V standard extended the main ATX cable to 24 pins to provide extra power to the PCI Express (PCIe) slots and doubled the dedicated CPU power connector to eight pins. When graphics cards began to demand even more power than PCIe slots could provide on their own, PSU manufacturers added supplemental six-pin PCIe power cables to the power supplies. In turn, some high-end video cards eventually required even more power than a single six-pin connector could provide, leading to PSU designs with eight-pin PCIe cables, six-pin twin cables, and even combinations of eight and six conductor pins that connect to either socket (sometimes called “6 + 2” conductors). Dual pattern splitter connectors commonly seen on modern power supplies (left to right): ATX / EPS motherboard power (20-pin / 24-pin), ATX12V / EPS12V CPU power (four-pin / eight-pin) and PCIe supplemental eight -pin / six pin (also known as “6 + 2”) Until recently, and with the rise of M.2 SSDs, most PCs had at least a few bay-mounted hard drives or 2.5-inch SSDs (and before that, internal optical drives) that followed the Serial ATA (SATA) standard. ). Separated from the SATA data cable, SATA drives employ their own discrete SATA power connectors, a thin “L” blade distinct from a connection that is keyed to insert in only one direction. Other internal peripheral devices, such as liquid-cooled water pumps and fan hubs, can still use the classic four-pin ATA power connectors. They are commonly called “Molex connectors” (but, contrary to popular belief, they are generally not made by Molex). Some sound cards and front control panels until recently even used the old four-pin floppy disk drive power connector. But that old-school connector is disappearing from modern power supplies. Most PSUs will have enough physical conductors for all the equipment you want to disconnect from a PSU of its power. But you want to make sure you double-check whether you’re installing your PSU on a system with legacy hardware or building a PC with a monster graphics card.

All mod cons: Understanding modular PSU cables

As more and more cables started coming out of the power supplies, it became more and more obvious to PC developers and developers that keeping the unused ones in a big wad between the PSU body and the case was not a good thing. option. That’s why most high-end power supplies these days use modular cable connectors: that is, cables you can plug in when you need them, leaving out unused ones to reduce clutter. Power supplies that have only detachable cables are called “fully modular” PSUs and those with some permanently attached cables are called “semi-modular”. Why not make all cables modular, on all projects? The added socket connections increase cost, provide some resistance and reduce efficiency, which is why so many high-end power supplies include at least one main soldered (24-pin) motherboard cable. (After all, everyone will need to use at least this cable on any PC.) Fully modular, 100% detachable cable designs only make sense to PC builders and modders who use custom length cables and may want to replace the 24 wires with the main cable with something shorter. Be aware that although some power supplies from different PSU manufacturers use the same modular connector style (and cables from one brand may fit in the chassis of another PSU), not all of them are connected in the same way. Users should only connect modular cables that are specified to work with their exact model or series of PSU. Don’t take mysterious modular cables from your parts box and plug them into a different modular power supply, hoping they will work – unless you like fireworks and want to buy new PC parts! As noted in final from the previous section, when evaluating a power supply, you need to look at installed components and peripherals that require a dedicated power connection. Most modern PSUs will provide more than enough connectors to supply any reasonable amount of SATA devices or auxiliary Molex powered peripherals. The main “question mark” connectors will be PCIe – specifically, how many you get on a given power supply. You will want to make sure you have the necessary cables for any graphics card or cards you are installing. The “6 + 2” connectors we mentioned earlier can be plugged into a six- or eight-pin video card power socket. A PCIe power cable with only six pins, however, will not be sufficient for an eight-pin receptacle on your video card. Note that some high-end video cards currently require three six- or eight-pin PCIe power cables, and only some high-power power supplies provide this. (Some might give you just two.) Please share this article if you like it!

Final note

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