Explanation of power connectors

[kenner]

I have done simple upgrades and put together a PII machine, no problem. Now on to a P4. The board is an ABIT BH7. The manual instructs me to shut off all power for one of the steps "including the 5V standby power" I'm lost! I can turn off the power switch in the back, turn off the power strip, but where is the 5V standby power. Are they talking about the P4 power connector? I am assuming in P4's you use either the P4 power connector or the 20 pin power connector, not both. Are there any other major differences in building up a P4 versus PII's or III's? Any recommended websites on do it yourself pc's, especially P4 would be appreciated.

[saphalline]

The best way to make sure no power is going through a mobo is to completely unplug it - there is no way to turn off just the +5V standby. Also, to prevent you from making a big mistake, you will need both power connectors!!

On a P4 mobo (and some Athlon mobo's), there are two that need to be plugged in. The main one is the ATX power connector, the 20-pin long rectangular thing. This is the replacement for the convoluted 2-part AT power connector and must be plugged into any ATX-class mobo. The second power connector is used specifically by the processor. It's the square 4-pin thing that delivers the massive amount of +12V electricity needed by modern CPU's (well, "massive" is relative :p).

[Beta Geek]

I've heard that leaving the power cord attached, but turning off the switch on the PS (if there is one) is better because it cuts the power but still grounds the case. Of course, if you don't have a kill switch on the PS, you should unplug it.
Also it's a good idea to push the power button after unplugging/flipping the PS switch to drain any juice lingering in the capacitors.

[saphalline]

Be careful of using the word "grounded"! Grounding something is merely relative to something else. If your mobo is grounded in relation to the earth but you have a charge (pos or neg), goodbye mobo! The point is to make sure you and your system are grounded relative to eachother. If you both have a -200V charge, no prob because the potential difference is the same.

That's why wrist straps are so popular, because they take all the guesswork out of relative grounding.

[Beta Geek]

Thanks for clarifying that! I forgot to make sure it was understood that you can't use any ground.... This is an extremely dangerous mistake that has been evidenced a lot in networking two buildings together. If they have a different grounding potential, you could kill yourself by simply touching a device that is grounded to one building, while holding a shielded connector that is coming in from the other building and therefore has a different reference ground. Optical fiber eliminates this risk.
As a rule of thumb always be extremely careful when working on power supplies, CRT monitors (which is not recommended unless you really know what you are doing), etc. Another thing, always wear the wrist strap when working inside your system, but take it off if you have to do any work on a PS, or CRT.