How much amperage do the 7800GTX and 7800GT need ?

"Skybuck Flying" wrote in message news:dl1q3o$oai$ snipped-for-privacy@news1.zwoll.ov.home.nl...

The problem is a question of how you 'measure' a current 'rating'. If you look back in time, to the old IBM supplies for the original PC-AT, these were 'rated' at 135W, conversely many of the 'clone' supplies at the same time, were rated at 220W, yet the IBM supplies often ran systems fine, while the latter showed problems with poor regulation. The reason was that the IBM 'rating' was what the supply could deliver at the connectors, with less than 5% change in regulation, while the 'clone' suppliers were uing

10% change, and often at the supply itself. Given that a couple of rails required regulation better than 7%, on the actual board, the IBM supply was often giving better performance than the supposedly more powerful 'clones'. The same trend has continued since, with the manufacturers with 'good' reputations, having much more margin in their specifications, than other units. Now the big problem with cards, CPU's etc., is not only their 'continuous' power consumption in heavy use (the 97W/118W figure), but the rate at which this can change. If (for instance), the card switches from an almost idle state, to doing a heavy rendering task, the load can jump from just a couple of amps, to nearly 10A, in a few uSec. The question is how well a supply can maintain regulation when there is this sudden change?. Supplies built for heavier outputs, will tend to have larger reservoir capacitors (slowing the rate at which the rail voltage changes), and heavier driver components, allowing the circuit to actually cope better when there is such a change. A good analogy, would be wooden boards on a scaffolding. Heavier boards, not only allow bigger loads to be supported, but if a load is suddenly dropped onto the boards, they 'spring' less, with the sudden change. It is possible to design supplies to give better behaviour for this type of change, but 90% of PC supplies on the market, are sold with ratings that they can only just generate, and small margins... Hence for good reliability, it becomes necessary to build 'margins' into the specification, and 'overrate' supplies by perhaps 20%. Some manufacturers do give 'real' figures, and (for instance), it is perfectly reasonable to use a Artic Cooling 350W supply on a system that needs over 300W, while conversely, many of the 500W 'clone' supplies, can only just about handle the same requirements...

Best Wishes

1 godzillabiggagigawatt

[snip]

And your response? You sound like a village idiot to me.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

I believe that you need to read the formula more carefully.

typical black american response

rail/connector

Indeed this site uses yet another formula:

Watts = Amps x Volts x Length

Bye, Skybuck.

Or French ?:-)

Have you heard what trouble the French are into now? Seems the terrorists burned down the white flag factory ;-)

...Jim Thompson

Me too ;-) Laughing too vigorously over your reply ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

With that name he probably is one.

John Lewis

- Technology early-birds are flying guinea-pigs.

Makes on wonder who surrenders first when both sides are French.

On Sat, 12 Nov 2005 18:17:05 +0000, John Lewis wrote: ...

The early bird gets the worm, which is fine if you like worms for breakfast. ;-)

Cheers! Rich

You owe me for a new coffee cup, keyboard, shirt, pair of pants and carpet :-)

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

Or the governor of Florida...same difference...

Or just look here ...

Hmm, wellwouldyalookathat ... there's my 600w seasonic on the recommended PS list :-)