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Athlon Power supply in the how to article
billcat Mar-07-00 06:09 AM
I have some serious problems beleaving that anything smaller than a 350W power supply would be enough to run a Athlon properly and even 350W depending on the brand is questionable. Granted that for running a web browser or utilitys and other low demanding software wouldn't be a problem but putting a cpu/video intensive game or software through it would result in lockups or general errors and unstabiltiy.
It's quite simple if you look at what a Athlon requires and what a power supply gives, the should at least equal out but I prefer a 5% power reserve over the cpu just to be sure.
The Athlon 600mhz cpu (A example speed) has been rated to pull 55W. It runs at 1.6v normally. To get the cpu to do this would require a power supply to supply 34.375Amps. This isn't counting todays video cards which can use another 10+ Amps easy. Add a SCSI card, the chipset and memory, the power waste of the switching regulator and you have a lot of current being demanded. If this computer is run at intensive operations it will exceed most power supplys current capacity short of a 400W supply. This is pretty straight forward math. It may never reach a 30Amp draw but it's not hard to do it either and with people overclocking crazy if they bump the voltage up on the cpu and bump up the video cards freq. there goes the ballgame. I bought the PC Power and Cooling 425ATX model because I play games on my computer. It gave me problems with the 300W supply that came with the case and these went away when I added the power supply. I'm sorry but recomending anything under 300W for a Athlon is just not good. It doesn't add up for stabilty over it's normal operation or add any leeway for upgrades and to even think of putting that new voodoo card that uses 4 video processors into that system is asking for trouble. You would have to buy another power supply only costing more money than buying the right type the first time.
Nice to see someone adding a ground strap to a article though. I've seen a few video card memory's wasted that way.

1. RE: Athlon Power supply in the how to article
lbyard Mar-07-00 09:01 PM
In response to message 0
I agree with some, but not all of your arguments and have modified the How To Build Your Own Athlon Computer. I have, indeed, extensively tested the MSI MS6167 motherboard with a 650 Mhz Athlon Processor in an AOpen HX45 case with the 235 Watt power supply that came with it and it was quite stable for days. However, that computer was my computer and was not as heavily loaded as the one built in the article (it did have a Diamond V770 display adapter with 32 Mbytes). From my experience, I still believe the 250 Watt ATX power supply which comes with the HX95A case is sufficient for most computers built with the MSI board and a 650 Mhz Athlon. Upon further reflection, however, I think it might be more prudent to use a quality 300 Watt supply for the loaded computer described in the article. The power supply we did use was on AMD’s recommended list. I do not believe a 400 Watt supply is necessary, at least when using the MSI board and a 650 Mhz Athlon. Proof of that is that the computer which was built with the Antec 300 Watt supply has been working just fine for more than six months. Although, the 650 Mhz Athlon specs state that the CPU typically dissipates 48 Watts of thermal power, and, obviously, DC power is the product of current and voltage, I find it rather difficult to believe the processor draws anywhere near 30 Amps and imposes anywhere near that kind of steady load on the power supply. From what I can gather from the AMD spec sheets, the current discussed is a transient current which can vary from 3 to 35 Amps. I would presume all of the 22 million transistors on the chip would have to be on simultaneously to pull the full maximum and that the steady-state load imposed on the power supply is much less. Please note that AMD has quite a few 250 Watt power supplies on their Recommended Power Supply List for the Athlon (http://www1.amd.com/athlon/power). The 250 Watt AOpen power supply is rated at 14 Amps on the 3.3 volt line and 25 Amps on the 5 volt line for a “combined power” of about 170 Watts. That compares quite favorably to the ratings for other power supplies on the AMD list. Larry

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