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Old 08-19-2006, 10:40 PM   #1 (permalink)
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Default what are dual 12v rails

what are dual 12v rails. i know that some powersupplies have 1 12v rail and some have 2. are powersupplies with dual 12v rails more powerful. i have seen 500w antec powersupplies with dual 12v rails with 19amps on each rail which totals to 38 amps. but i have a 500w powersupply that only has one 12v rail but it has 38amps on one rail. so do both powersupplies have the same amount of power. and if both powersupplies have the same amount of power, whats the point of dual 12v rails.
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Old 08-20-2006, 01:21 AM   #2 (permalink)
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Dual 12v Rails generally provide more support and power for higher end machines with SLI or a big power hunger GPU (I think this is it however I could be wrong). Please correct me if I am incorrect.
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Old 08-20-2006, 01:39 AM   #3 (permalink)
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Indeed, seperate dedicated power for SLI and the CPU.
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Old 08-20-2006, 01:52 AM   #4 (permalink)
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On newegg if it says it has dual 12v, that pretty much means its SLI ready, Nvidia just didn't put their seal of aproval on it for whatever reason. However not all cards need it. Mine takes regular 4 pin connectors so I don't need anything special.
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Old 08-20-2006, 12:23 PM   #5 (permalink)
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but on powersupplies with dual 12v rails each rail has 19 amps. but i have a 500w powersupply with only one rail and it has 38 amps. so do both of the power supplies have the same amount of power.
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Old 08-21-2006, 06:02 AM   #6 (permalink)
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multiple power rails are part of the ATX 2.0 specification i.e. to be labelled ATX 2.0 compliant a PSU must feature at least 2 power supply rails. a rail is basically a seperated power source, so dual 12v rails mean that the 12v connections are supplied from 2 sources. in the case of a psu with only dual rails one rail is dedicated to the mainboard via the ATX connector/P4 pin and the other is dedicated to the other power connectors which may be used to power the motherboard as well as graphics cards and other peripherals.
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Old 08-21-2006, 07:26 AM   #7 (permalink)
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Quote:
Originally posted by bum
On newegg if it says it has dual 12v, that pretty much means its SLI ready, Nvidia just didn't put their seal of aproval on it for whatever reason. However not all cards need it. Mine takes regular 4 pin connectors so I don't need anything special.
No, no.. that's not how it works. I have a dual-rail PSU that came with a 30$ case, and is by no means SLI ready.

Dual-rail means there is two 12v circuits. It's basically as simple as that.

It's like having two breakers in a fuse panel. One would easily overload if you put too much strain on it. The same with PSU's. You can't provide enough amps to run everything required, so, they made an additional 12v rail to provide more amps and to provide more headroom for more devices.
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Old 08-21-2006, 07:59 PM   #8 (permalink)
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so would two 19amp rails be the same as one 38 amp rail?
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Old 08-21-2006, 10:47 PM   #9 (permalink)
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Quote:
Originally posted by j369852147412
so would two 19amp rails be the same as one 38 amp rail?
Kind of. Each rail would have 19a to offer, creating a peak amp of 38a. 38a is the absolute most you can take off the 12v circuit.
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