Startingover I can feel your stress and your willingness to learn...learn...learn.
Okay here's the beef.
I am going to post a picture below that shows the guts found inside a basic power supply, so here goes.
You can click that image above and it will somewhat blow up a bit for clarity if you wish.
Any how, if you examine that image above and you take notice of the silver colored long metal things (there is two of them and those are called heat sinks) and try to look behind the large black cylinders and to the left of the yellow transformer, you will notice a slight view of what is called a bride rectifier (the black colored thing attached to the heat sink, a series of diodes that take an AC current from each branch off of the down-step transformer (That's the yellow colored square thing in between the two silver things) those rectifiers also have built in voltage regulators, which regulate the current so it is at a constant flow at a constant rating, it does not fluctuate or deviate from the specified rating.
That current is then passed through a series of filters which are those large round cylinders which are called electrolytic capacitors to filter out the AC ripple, this leaves us with a pure DC signal at the output.
Now going back to the transformer again, the transformer has a series of copper wire which is coiled around a ferrite core and a frame. The input is a pure AC sine wave of around 115 to 120 Volts AC (house current) AC stands for Alternating Current, it alternates in a manner so that neither is just Positive or Negative, it can be either. The job of a Power supply is to do two things, first, it drops the current to a safe usable level, second it filters out the harmful AC which is unstable and vary noisy.
As the AC is passed through a down-step transformer, there are various stages where it is tapped into, these taps intercept the AC current at different levels of the coil where it picks up the different voltages, those are fed into a diode network called a bridge rectifier, it is through this network you obtain the AC voltages of 3.3 5.0 and 12 volts, The diodes are put in such a network that they form a square, a square with four corners, if you look at the square, each point of the square can be labeled, commonly the symbol ~ is used for AC, then + and - are produced where the diodes block part of the AC sine-wave.
So basically, as you go around the corners of the square you would have ~ + ~ -
The + is the POSITIVE phase and the - is the NEGATIVE phase.
This is done for each network, 3.3, 5.0 and 12.0 Volts.
The result still has AC present, so a series of large electrolytic capacitors are put into the circuit between the + and -
Because these devices are polarized and they store a current like a battery, when the pulse attempts to go negative, the capacitor discharges a positive pulse into the output, when the pulse attempts to go positive, the capacitor injects a negative pulse into the output.
This result removes the AC ripple by creating a solid wave form rather than an alternating one, POSITIVE (RED) remains POSITIVE, NEGATIVE (BLACK) remains NEGATIVE.
If you are a bit lost here, think of an AC wave form as being like the letter "S" laying on its side.
Such as this image below.
An Ac sine wave has a ripple, where as DC runs a straight line of the POSITIVE pulse above the center line and a straight line of NEGATIVE below the line, the figure "S" is removed.
In computer systems, the term "RAIL" is used to describe the (Transformer, rectifier
, electrolytic capacitor) network I spoke of above. If you have ever seen the rectifier which is mostly hidden out of view in the image above, you'd understand why the term "rail" is used.
I explained it as basic as I possibly can, as there is much more circuitry involved in a power supply than what I mentioned here, such as resister networks and such, but going into that will only draw this post on and on.
As for digital, digital is basically a state of it's either on or it's off.
Yeah I know confusing isn't it?
Basically IC chips are based on logic, their state involves being either Neutral or grounded to create the OFF status.
When the state goes HIGH or POSITIVE its state is said to be ON.
IC chips are now being incorporated into modern day power supplies, because they produce a much cleaner DC signal than the older bridge rectifier types.
As far as answering this question you asked: What is CrossFireX & SLI?
This is a new technology that allows two video cards to be put into a motherboard that has two PCI-E X16 slots side by side, this allows running dual monitors, one on each slot and card.
Check this image below.
As you can see from my image above there are two video cards placed side by side those are Nvidia brand SLI cards to which as you can see have a circuit board connecting them together at the top as well as both being in a PCI-Express slot on the motherboard.
Sorry for the long lecture, but it is my hope that I have demystified your curiosity a bit in the process.
Edited by MrBruce1959, 06 May 2011 - 03:25 PM.