MicroMina :
i dont know why i cant understand!!!!
I need someone to tell me like:
for 12v : 40 amp minimum
for 5v : 20 amp minimum
and so on
OK. Let's try again.
We have two problems here. First, you are really inexperienced. And second, since you live in Egypt, we cannot just tell you, "Go to newegg and order either this PSU or that PSU. Either will serve your needs nicely."
And I suspect that you have a third problem that I think everyone who is trying to help is unaware of. I am living and working in Saudi Arabia. When I go downtown PSU shopping, what I find falls into 3 categories:
1. Junk: 50 to 60 Saudi riyals ($15 US)
2. Inexpensive: 100 to 150 SR ($30 to $40 US)
3. Expensive: Good brand names which cost about 1.5 times as much as they would in the U.S.
If you are in that situation, that is bad for you because you are at the mercy of the salesman.
Before I continue on, two questions:
1. What brands are available where you live?
2. How warm does the room (where the computer will be) get in the summer? (Trust me, this is relevant.)
I am going to assume that you know a little about electricity - watts = volts multiplied by amps. OK?
If you look at a label on a PSU or a PSU box, THe total wattage will be more than the rating of the PSU. The important rating is the 12 volt capacity.
Do not worry about the 3.3 volt or the 5 volt capacity. 3.3 volts powers the memory subsystem and the digital part of SATA drives. 5 volts powers the motherboard (except for the CPU) and the digital part of any drives. I have a full featured motherboard, 3 hard drives, and a DVD burner. I would be very surprised if I am pulling 100 watts total off the 3.3 and 5 volt outputs.
The 12 volt output is the real workhorse. I tend to use conservative, high side estimates (military electronics background). I figure 10 amps for the CPU (15 amps if you are overclocking). And I figure 20 amps for most upper end video cards. Figure 5 amps for 2 or three drives.
Here is a practical example of what to look for. I just happened to need a replacemant PSU for Box #2, and i just got back to the house and started answering your post.
I picked up a 500 watt Coolmax (and before the rest of you tell me where Coolmax sits on the Tier List - I know).
Anyhow:
+3.3 v 28A +5 volt 30A +12 volt 18A and 16A Total 12 volt 31A The other outputs do not really matter.
Antec 550 TP3 (bought on sale for about half price ($45)
+3.3 24A +5 volt 24A +12 volt 3 X 18A rails total 42A
For only a 50 watts higher rating, the Antec has much more usable power for a modern PC. The 550 watt Antec would power Box#1 quite nicely. I would not even try to power Box#1 with the Coolmax PSU. And the Antec is rated for full output at 50 deg. C. This is such a difficult standard to meet that any manufacturer who can will tell you.
Try to get a good PSU. I would recommend at least 40 amps on the 12 volt outputs. Do not worry about the 3.3 and 5 volt outputs. Also do not worry too much whether or not the PSU has a single large rail or multiple smaller rails. One of the best PSU manufacturers in the U.S. favors a single massive rail and will tell you why.
Also, try to get a PSU that has the proper connectors for what YOU are going to use with it. You can always get adapters, but with a little planning, you shouldn't need to.
I could have done a short post consisting of the last two paragraphs above. But someone else, with equally good reasoning, could have recommended 30 amps on the 12 volt rails. And you would be confused, "jsc said 40 amps. The other guy said 30 amps. The estimates are pretty far apart. Who do I believe?" But you now know why I said 40 amps.