Quote:
Originally Posted by glatt
Seems to me you should add up the peak values for all the components, and get something that is equal to that number. Since it's unlikely that you will find a power supply with exactly that number, you should buy the next size up.
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Which is what engineers at HP and Dell have done for decades. His 800 watt supply would never see a 400 watt load. Similar computers from those manufacturers only need 200+ watt supplies to power every future part. These numbers are easily calculated since every peripheral connector (ie PCI or video card slot) and other connectors are limited to so many amps. Add all up and lower wattage supplies selected by HP and Dell engineers are more that sufficient.
Getting a layman to add those numbers is virtually impossible for a majority. Simpler to tell him he needs a 600+ watt supply and sell him an 800 watt supply for a computer that never consumes even 300 watts.
Watts is a useless design number. Current (amps) for each DC voltage is relevant. But most computer assemblers (amazingly) cannot add those numbers. Easier is to sell supplies on watts.
Some power supplies are rated at their output power. Others rated for how much is consumed. So a 250 watt power supply from a major manufacturer might also be sold as a 350 watt supply to computer assemblers. Nobody lied. Just another characteristic played with numbers that explains why many are told to buy an 800 watt supply - when a 200+ watt supply is more than sufficient. If he really needed a supply anywhere that large, then his computer can also toast bread.
This game continues. For example, I recently purchased a used power supply to fix a computer. That supply marketed to computer assemblers as ATX was missing essential parts necessary to make it ATX compatible. No problem. Holes for missing parts were occupied by jumpers. Parts removed from a defective supply replaced those jumpers to upgrade the new supply with ATX required functions. Supplies missing essential functions are extremely profitable since so many assume all ATX functions exist only if a computer boots.
Another feature of the game. Legally, only a computer assembler must know and meet industry standards and Federal regulations. If a power supply is missing those functions, then the computer assembler (not power supply manufacturer) is legally responsible. Many ATX power supplies are missing essential features that, for example, mean a power supply failure cannot and will not harm other computer parts. Then naive consumers actually believe a motherboard or disk drive damaged by a failing supply is acceptable. ATX standards define functions that make damage impossible. But some supplies are marketed missing such functions. Especially easy when the supply does not come with that long list of specs.
Step one for selecting any supply is a long list of numeric specs. Irrelevant is even if a consumer does not know what those numbers mean. If that long list of specifications is not provided, then a supply can be and may be missing essential and required ATX functions. And the few who actually know what those numbers mean cannot 'blow the whistle'. Unfortunately, most computer assemblers see a computer boot. That proves all ATX functions exist? No. But most consumers assume otherwise only because it boots.
An industry phrase (forgot the symbol) is now marketed that says a supply meets ATX standards - that is not missing essential functions.