I got this older computer(celeron850/192mbRAM/20gig HD/CD/Floppy/‘all-in-one mobo’) that was being replaced. I took it home to rebuild it and found out that it ran perfectly on a whopping 155Watt PSU.
I got this cute little discarded cel400 computer lately. Took a look inside, and there was this tiny 112 watt PSU. Came with HD/CD/Floppy/mobo with sound card, network, and modem. Just for fun, i decided to put in a 600mhz PIII and a second CD drive in there.. and it worked fine. No crashes, worked great.
So.. just how much power does a mobo, CD, HD, and floppy need(separately)? I know that CPUs have their wattage rated.. but none of the other stuff do.
Also, with power supplies, a great analogy I recently heard:
With car engines, it’s fine to have them run in the red line sometimes, but not all the time. The same is with power supplies: running them at the max or close to is not good for the long-term life of the unit.
The other factor with power supplies is the voltage rail in use. There’s 3 main ones: +3.3V, +5V, and +12V. Most newer units have at least 2 +12V rails due to many of the components drawing off the +12V: CPU, PCIe video cards (and any auxillary power requirements), SATA hard drives. RAM runs off the 3.3V…well, for the most part (DFI has some motherboards that allow for heavy overvolting by switching over to the +5V rail to provide up to 4V on DDR). AGP cards would also draw from the 3.3V. +5V used to be for CPUs, but for power requirements, they had to be moved over to the +12V.
I didn’t either, but, even then, you don’t want your system consuming 400W and only provide just enough to power it. With newer setups, the +12V is the star, but with older systems, the +5V followed by the +3.3V and then the +12V were important. We started seeing this transition with the Pentium 4/Athlon(32-bit) era.
