Do harddrives and RAM use the 12 volt rail

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polis_putrus

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Im upgrading my computer and I included EVERYTHING in my wattage calculation for the 12 volt rail, but do I need to include the Harddrive, RAM, fans, mouse and keyboard?
 
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Rule of thumb is to add ~50W for miscellaneous stuff like HDDs and call it a day. You should be picking a PSU with a bit of headroom above whatever you calculate for required power anyway, such that a few watts here and there shouldn't make a difference.
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jimmysmitty

jimmysmitty

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Mouse and Keyboard will pull from the USB. Normally USBB uses 5V.

Hard drives, a spinning disk, will use 5V and 12V.

Fans do use 12V. Usually they use about 1.8 watts. Maybe more or less depending on if its PWM and/or has LEDs.

Memory only uses between 1.20 to 1.5v. I believe DDR4 is normally 1.20v with overclocked kits typically pushing slightly higher. It most likely is pulling from the 12V rail but that is all done and dropped via the motherboard to the required voltages.

I always suggest to go over what you expect to need. For example if a GPU states recommended wattage of 500W I would do 600W. That would more than cover additional peripherals .
 
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TJ Hooker

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Rule of thumb is to add ~50W for miscellaneous stuff like HDDs and call it a day. You should be picking a PSU with a bit of headroom above whatever you calculate for required power anyway, such that a few watts here and there shouldn't make a difference.
 
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polis_putrus

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I have an Optiplex 745 Small Form Factor and the only changes Ive made: disconnected the CD drive so it doesnt use any watts, I never used the CD drive anyways, upgraded from 3GB RAM to 8GB, and I bought an AMD Radeon R5 240 1GB Low Profile, the CPU is still a Core 2 Duo E6400
 
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polis_putrus

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oh, thanks, I never thought about looking at the stickers.
 
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