Once upon a time, PSUs didn’t extend a veritable mass of cables to their installers for installation and use. A motherboard cable bundle with an AT or ATX modular connector, and up to half a dozen Molex connectors for hard disks and floppy drives was just about it. But today’s modern PCs and their constituent components demand considerably more. Here’s what you’re likely to see provided on most higher-end PSUs nowadays:
- 20-pin “old standard” ATX motherboard connector or 24-pin “new standard” ATX motherboard connector (the 4 pins added are to provide power to the PCI-E port for a graphics card). Most newer motherboards sport 24-pin connectors, so buy a compatible PSU (this standard is called ATX 2.0, and its latest version is the ATX 2.2 specification; be sure to look for 24-pin ATX connector support especially if your motherboard has a PCI-E X16 graphics slot and you plan to use it).
You can indeed buy an adapter to plug a 20-pin connector from a PSU into a 24-pin connector on the motherboard (in fact, they only cost about $4). But this puts a serious strain on your power supply and its electrical connections to the motherboard. It might do in a pinch, but it’s not recommended. The absence of a 24-pin connector may mean that the PSU conforms to an earlier specification (ATX12V v1.3, for example), which has considerably different requirements than the latest specification.
- 6-pin PCI Express power cable for a PCI-E X16 graphics card. If your PSU doesn’t have one, nor a 24-pin motherboard connector, you can buy an adapter that will let you draw power from two unused 4-pin Molex outputs from your PSU (assuming you’ve got them to spare) and then plug into the 6-pin power input on the graphics card.
- 4-pin Auxiliary 12 V ATX power cable for square motherboard connector. This provides power to the CPU and should never be used to make up for the 4 “missing pins” on a 20-pin connector.
- One or more small 4-pin power connector(s) for floppy drive(s). If there’s more than one, they may be daisy-chained on one or more power cables (often with 4-pin Molex connectors for hard or optical disks)
- Four or more 4-pin Molex connectors for hard or optical disks (the 500 W power supply under examination as we write this chapter has 8 such connectors and can handle eight drives with ease).
Check your parts and save receipts! Making sure things fit may take a little effort, and it may even require you to return a purchase should you discover a mismatch. That’s why it’s always a good idea to lay out your parts and match connectors up by eye before you start putting them together. That’s also why it’s smart to save all receipts and to make sure you can exchange or return items that don’t work out. Continued…