On Fri, 2004-09-03 at 14:52, Harvey Alaric wrote: >I plan to buy a PC case with power supply. I see some advertised >with a 550 Watt power supply, which seems like a lot. Is more >better or is it possible to have too many Watts? Hi Harvey First of all, the power output from a power supply depends on the temperature inside the power supply. A power supply rated as 550 Watts at 25 degrees Centigrade may only supply 366 Watts at 40 degrees C., which is not an unrealistic temperature for the inside of a PC power supply. Secondly, power supplies are more efficient and reliable when loaded to less than 70% of maximum capacity. So a 550 watt supply might be ideal for a system that only needs 275 watts but is hot inside the case. Thirdly, different power supplies supply differing amounts of power at the various voltages needed by the computer. (I'm talking about 3.3 volts, 5 volts, and 12 volts.) A computer with a large number of hard drives, CD-Rom or DVD-Rom drives, CD or DVD burners, etc. probably needs extra power on the 12 volt lines. (The drive motors run off 12 volts.) A computer with a super video card or power hungry CPU might need more power from the 3.3 volts and 5 volt lines. (The logic stuff on the motherboard, video card, PCI cards, inside the processor(s) and in the circuitry of the disk drives uses 3.3 and/or 5 volts.) An older 600 watt power supply meant for a system with a ton of disk drives may not supply enough power at 3.3 volts and 5 volts for today's P4 or Athlon systems and high performance video cards. A system with ten disk drives might not get enough power from a power supply that supplies a disproportionate amount of its power supply at 3.3 volts and 5 volts. So the safest solution might be to get a power supply that seems overpowered. It should run more efficiently and would hopefully supply sufficient power at all voltages. For an idea of how much power you need for the components inside your computer, check out the following webpage: http://www.pcpowercooling.com/maxpc/cases.htm You could keep count of the power needed at each voltage and compare the three totals to the specification sheets of prospective power supplies. To answer your question, you can never have too large a capacity power supply. Final comments: Over the years, I've come to hate cheap or insufficiently powered power supplies. Most of the troubles I've had inside my computers have been power related. All the disk drive problems I've ever had have been due to bad power cables or insufficient power. Same with power to the motherboard. Reoccurring Windows blue screens have been solved by replacing the power supply. I've had power supplies slowly die over the course of a month or two and I've had power supplies die suddenly with a loud crack and smell of smoke. I suspect however that few people are willing to spend the money for a high quality large capacity power supply. Regards, Bill The NOSPIN Group Promotions is now offering Mandrake Linux or Red Hat Linux CD sets along with the OpenOffice CD... at a great price!!! http://freepctech.com/goodies/promotions.shtml