I was recently building a PC box for someone where I was buying the CPU / mainboard new and using other components 2nd hand. That means I had a 2nd hand case and PSU. Now, the 2nd hand components arn’t that old, else I wouldn’t use them for someone elses PC.

The 1st problem I ran into is that the new AMD X2 board I bought (Gigabyte M6TPME-S2) uses a 24 pin power connector. It took a bit of Googling, but I found a many people saying that you can plug the old 20 pin ATX connector into the 24 pin port. And it’s true. Actually it does mention that in the mainboard manaul, right alongside where it says “It is recommended to use a 400W power supply otherwise the system may fail to boot”

The best article on power I found covers some nice history of power in computers. Now, I was going by guide of the 20+4 pin ATX connector that the additional 4 pins are on the left hand side of the connector with the locking mechanism facing away from me. But if you read the section on the 24 pin connector, they have actually adjusted the holes to use a round / square combination so the 20 pin connector will only fit in one way. Thanks!

So even though it’s a 300W PSU with the additional 12V (“P4″) cable, the system booted. Kind of. It powered on, but would not POST and would not power the video. Guess I need that 400W sigh.