What’s the difference between a 20-pin PSU and a 24-pin PSU?



October 9th, 2006

What's the difference between a [tag]20-pin[/tag] [tag]PSU[/tag] and a [tag]24-pin[/tag] power supply unit (PSU)?

One has a 20-pin [tag]motherboard[/tag] connector, the other has a 24-pin connector! 

OK, there's a little more to it than that.  The 20-pin connector is the older [tag]ATX[/tag] 1.x standard while the 24-pin connector belongs to the newer ATX 2.x standard. 

Here is the pinout of the 20-pin power connector:

Pin Name   Color Description
1 3.3V   Orange +3.3 VDC
2 3.3V   Orange +3.3 VDC
3 COM   Black Ground
4 5V   Red +5 VDC
5 COM   Black Ground
6 5V   Red +5 VDC
7 COM   Black Ground
8 PWR_OK   Gray Power OK
9 5VSB   Purple +5 VDC Standby Voltage (max 10mA)
10 12V   Yellow +12 VDC
11 3.3V   Orange +3.3 VDC
12 -12V   Blue -12 VDC
13 COM   Black Ground
14 PS_ON   Green Power Supply On.
15 COM   Black Ground
16 COM   Black Ground
17 COM   Black Ground
18 -5V   White -5 VDC
19 5V   Red +5 VDC
20 5V   Red +5 VDC

Here is the pinout for the 24-pin connector:

Pin Name   Color Description
1 3.3V   Orange +3.3 VDC
2 3.3V   Orange +3.3 VDC
3 COM   Black Ground
4 5V   Red +5 VDC
5 COM   Black Ground
6 5V   Red +5 VDC
7 COM   Black Ground
8 PWR_OK   Gray Power OK
9 5VSB   Purple +5 VDC Standby Voltage (max 10mA)
10 12V   Yellow +12 VDC
11 12V   Yellow +12 VDC
12 3.3V   Orange +3.3 VDC
13 3.3V   Orange +3.3 VDC
14 -12V   Blue -12 VDC
15 COM   Black Ground
16 PS_ON   Green Power Supply On.
17 COM   Black Ground
18 COM   Black Ground
19 COM   Black Ground
20 -5V   White -5 VDC
21 +5V   Red +5 VDC
22 +5V   Red +5 VDC
23 +5V   Red +5 VDC
24 COM   Black Ground

Notice that the only difference are pins 11, 12, 23 and 24 (12V, 3.3V, 5V and a ground respectively).  You can get a cable that converts a 20-pin connector into a 24-pin connector (it just splits off an existing cable of the right type), but you will need to make sure that the PSU has ample power for the job at hand (check your manual).  If your motherboard needs a 12v auxiliary connector (which can be 4-pin or 8-pin) and your current PSU doesn't have one, you'll need a new PS (although if you have a 4-pin aux connector and you need an 8-pin one, you can get a converter for that too).

All that said, I generally find that it's less hassle to just get a new PSU rather than bother with converters because they add a lot of additional clutter inside the case.

This entry was posted on Monday, October 9th, 2006 at 15:13 and is filed under PC Doctor Repair/Upgrade Tips, Questions from Visitors. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

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