Just how much power does a computer need?

Yuchao719

Yuchao719

Geek
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.
 
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Hi Yuchao719 :)

I run a Akasa PaxPower 460w in my modded rig but only use about 270 - 280w

My spec

MoBo Asrock P4i45GV R5.0
Intel Pentium P 4 CPU 2.80GHz Ocd to 3 GHz
Cooler PSU Akasa PaxPower 460w
Master Premium Silent CPU Cooler - P4
Ballistix 2GB 2048MB Kit
Graphics Card NVIDIA GeForce 6600 GT Ocd 8% zalman VF700 Cooler
HDDs
Samsung SP1654N 150GB
Seagate Barracuda 7200 200GB
Sound Card SIIG SoundWave 7.1 PCI
Monitor Sony 19" x-black technology LCD SDM-HS95 P/R – DVI
Keyboard Logitech G15 Gaming Keyboard
Mouse Labtec wireless optical
Case lights - CC and LEDs

Click image to zoom

 
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.
 
Thanks for the info guys. That website was really helpful. And thanks Big B for pointing out the "red line" analogy - never thought of it that way.
 
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.
 
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