The newcomer is still too weak to replace the old -macho-4 pins peripheral connector. Obviously, it was not designed for this reason.
There are adapters that convert the old 4-pins peripheral power connectors to the new SATA 15-pins connectors. These adapters are unable to provide the +3.3V that the SATA power connectors have introduced, and therefore must be used with extreme caution.
This is the newcomer (since 2003) that will replace the old peripheral power supply connectors. No, it will not. It is very sophisticated connector, but due to its low current rating, all power supplies still have (and will have) the good old 4-pin molex muscle connectors, to power current draining devices. It carries the same features as it's ancestor, and also has a +3.3 volts line. Although it has 5 cables, it has internally 15 pins. It is physically polarized to avoid errors in connection.
Now here is a point that needs of your attention. This is something that most of the people i know are not aware of. When the power supply has no more SATA power connectors free, or no SATA power connectors at all and you need to power a SATA device, there are cable converters to convert from the old 4-pins to the new 15 pins (5 cables) connector. Do you notice something strange in the previous sentence? Yes, a cable is missing. These connectors are unable to supply the newcomer's innovation, the 5th wire with the +3.3 volts. Most of the times, the devices that are powered with such connectors, does not require external 3.3volts power supply, and believe me, this is not accidental. And as time passes, this is subject to change. So be very careful when using such adapters.
PCI Express power supply
PCI Express 6 pins power supply
For the power-demanding PCI express cards such as the graphic cards, the PEG cable provides three more +12v lines
Be extra careful if your power supply does not have a PEG cable and you use a market cable converter. It comes with two 4-pins peripheral connectors that MUST be connected into separated lines from the power supply!
This connector is used to power demanding cards in PCI Express slots. Such cards are usually the graphic cards. Some of them have more computing power than my laptop! The PCI express slots can provide up to 75 Watts. If more power is required, then this connector provides the power. And because usually the demanding cards are the graphic cards, this cable is called "PEG" (PCI Express Graphics). It can also be connected in an 8-pins PCI Express connector. It is designed to do it. Some cards may operate this way, some may not accept it, as they have enhanced sensor to check if a 6 or an 8 connector is connected. Some cards may accept the 6 pins connectors, but will reduce the performance accordingly. The connector is physically polarized to avoid errors in connection.
If your power supply does not have a PEG cable, then you can use a cable converter from the market. These converters have 2 separated 4-pin molex connectors that MUST be connected into different power supply lines.
PCI Express 8 pins power supply
The PCI express cards seems that have grown big. Actually so big, that the 6 pins 12V power connector was not enough any more. So, since 2007, the 8 pins +12V power cable was introduced. This cable can provide double the power than it's ancestor, that is up to 150 watts of raw power. This connector is also polarized to avoid error in connection.
PLEASE CONTRIBUTE! As i do not yet have any photos of an 8 pin PCI-E and a 6+2 PCI-E cable, i search for original (AND ONLY ORIGINAL) photos with analysis larger than 1600x1200. Please email me! Webmaster. Do not confuse this connector with the 8-pins 12V power supply connector, as their polarization is different.
@Roger Cole for small signals you may wanna use RJ connectors, like the ones used on telephones and ethernet cables. They come in different sizes with 2,4,5,8 wires and they are pretty small. This is what i would use for small signals. For high current rates, polarized headers such as these are ggood:
Great resource as has been said. I am looking for a plug/socket to adapt a six-wire 12v house thermostat controller. Based on reading this, (a) I can forget about using the ATX 6 pin as being too rare but (b) looks like I could use two peripheral 4-pin plugs or (c) the PCI Express 6=pin. The latter looks like overkill for the small signals and currents there will be and I am thinking option (b). Any thoughts appreciated!
@Mark Green each connector has a different key, so that they cannot be connected wrong. You may wanna check the keys to ensure that they do connect there. If you see closely the conneters you will notice that each pin may be rectangular, or like a roof top. The same "keys" applies to the the connector receptacles on the motherboard. This way, you cannot put wrong connectors.