480 Power supply

[mikayd]

im buying an AMD Athlon 64 X2 3800+ 1GHz FSB 2 x 512KB L2 Cache Socket 939 Dual Core Processor can a 480 power this

[redwudz]

I use a 480W in my AMD64, running 4 hard drives, DVD burner and ROM and a CD burner, floppy, zip drive, along with three 80mm fans.

Should be more than enough power. More important is the quality of the PS. Some really cheap ones are overrated. It's worth it to get a name brand quality PS to protect your investment in your computer.

[rallynavvie]

Should be more than enough power. More important is the quality of the PS. Some really cheap ones are overrated. It's worth it to get a name brand quality PS to protect your investment in your computer.

+1

Antec is one of the generally-accepted standards for power supplies. Their new TruePowerII series or the NeoPower PSUs are excellent. I have a 480W NeoPower in my dual Athlon rig and an Antec TruePowerII 550W EPS power supply in my Xeon rig. Both of them push plenty of peripherals so you shouldn't need to worry about filling that box up. Maybe if you had two power-hungry video cards running SLI in there you may want to bump up higher. Also check out PC Power and Cooling (the best PSUs on the market), Sparkle, and Fortron.

Stay away from Powmax, MadDog, and Thermaltake PSUs. I've witnessed the effects of the first two frying an entire computer and the last was my friend's PSU which he touted as the best thing for PCs since Super ISA. His was one of the expensive ones and it lasted all of three weeks continuous running and then puffed smoke while playing CoD2.

Keep in mind that the PSU is one of the most important parts of your system and all too often overlooked.

[SaSi]

480W is certainly more than enough for any kind of desktop PC.

My PC, with a P4/2.8GHz, 9xHD, 2Gb RAM and 7xFans consumes (as measured) 195W of power. My PC is now having a 350W PSU.

So, theoretically, even a 200W PSU should be enough, right?

Wrong.

What is more important than the advertised rating of a PSU is how much current it can provide at each voltage output.

The PSU will provide +3.3, +5 and +12V (main voltages of interest).

+12 volt goes to power the HD and CD motors (and fans) while +5 go to various electronics, including HD and CD/DVD. +5V also gets converted to other voltages in some motherboards.

+3.3 V will typicaly go to the CPU/RAM, after it is transformed to a lower voltage (typically in the 1.5V range).

The total power rating of the PSU is the sum of power output of all available voltages. However, if a PSU can only provide 30A in the +5V output, (meaning 30 x 5 = 150W), even if the total rating of the PSU is 400W, you only get 150W for +5V.

Let me give you a real experience from when I tried to replace my 350W PSU with a 500W model.

The 350W PSU was able to deliver 40A at +5V (i.e. 200W). The new 500W PSU was only rated at 30A for +5V (i.e. 150W).

Using the 350W model, I measured the output voltage at +5 and +12V (with a multimeter and not with the various m/b monitor utilities) and found +5 to be +5.09 and +12 to be +11.9

Using the 500W model, I did the same and found +5 to be 4.78 and +12 to be +12.20

What the above measurements mean is the following: When a PSU is stressed to deliver current, it automatically drops the output voltage to compensate (if the drawn power reaches or exceeds its capacity).

Therefore, the 350W model was capable of providing ample +5 power but less +12 power, while the 500W model was potent at +12V but lagging behind at +5V.

Undervoltage to the drive motors is not critical, especially if it is not significant (less than 5%). However, undervoltage to electronics can be a good reason for lockups.

This particular 500W PSU was designed to accomodate state of the art VGA boards hungry for +12V (another 12V consumer besides disks). It had all the usual connectors for powering VGA boards. However, I still use a humble GeForce4MX440 that draws very little power.

Additionally, my motherboard (Gigabyte GA8KNXP) seems to power RAM by converting +5V (leaving the +3.3V supply all to the CPU).

Therefore, my system needs lot's of +5V power (especially since I use lot's of RAM) but very little +12V.

So, I need a PSU that can deliver this. I believe it is clear that the total power rating is not only irrelevant but can also be misguiding.

When you select a PSU make sure you are aware of the power output (in Amperes - A) for each significant voltage.

As guidelines:
+3.3V should give at least 25A, better 30A. If you are using a power hungry dual core CPU, better have 35A.
+5V should give 30A as an absolute minimum. If you are using lot's of RAM and PCI boards, go to 35A. Better still, look for 40A.
+12V should give at least 20A. If you are using an expensive, power hungry VGA, go for more (e.g. 30,40A).

If you have access to a multimeter (if not buy one-it's worth it), use any available PSU with your machine totaly populated with whatever h/w you need. Then mesure the voltage at an available IDE disk power connector. The Black-Yellow cables provide +12V and the Black-Red cables +5V.

If you measure less then 5V on the 5V outlet, the PSU is streched for 5V on your system. If you measure more than 5V, it means that the PSU provides more than enough. Same for 12V.

Read the PSU's label which should state it's power output at each separate voltage.

Suppose the multimeter read 4.9V at 5V output. Also suppose the PSU reads 30A at 5V. As a rule of thumb, a 35A power output at 5V should compensate for the PC needs.

The rules for 12V are similar.

[redwudz]

SaSi, that's good information. Some of the cheaper cases that come with power supplies rated at 300W, I suspicion are just relabeled 250W supplies.

The simplistic test I use is to put my hand at the fan output of the PS and feel the temperature of the exhaust air. If it's hot, above 90F or more under load, I figure it's overstressed and unreliable. If you can smell hot electronic parts, you got a problem. My 480W PS runs about 70F, even under load, so my guess is it's sufficient for my needs.

If your motherboard comes with a voltage monitor program, it's good to check that for information, especially when you first power up the system. The program Motherboard Monitor or similar programs will also work with most motherboards for PS voltages and fan speeds.

It seems like 450W+ PS's are very common these days. And as stated, you go with a name brand like Antec, or similar, you will be much better off. Using a $30 US PS with a +$600 US computer system doesn't make much sense.

[ROF]

im buying an AMD Athlon 64 X2 3800+ 1GHz FSB 2 x 512KB L2 Cache Socket 939 Dual Core Processor can a 480 power this

I don't know. How many drives and what type will you be using? Which Graphics card are you using? Will you have daisy chained devices or self powered hubs connected? How about any add-on cards? Which Motherboard are you buying?

That being said without knowing those answers I'd still say a 480W PS is sufficient.