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Single rail 100% modular PSU's


Guest Kojak
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Guest Kojak

Ultra has the X3 and X4 lineup on single rail modulars. But people bag on em so silverstone is the next best bet lol

 

Thanks. I looked at the X4 1600.

With only a 76A rating, it doesn't compare well to the 95A Silverstone SST-ZU1200M

( which will power two 5970 GPU's ). Even my Corsair TX750 carries a 60A rating.

 

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Guest Kojak

Personally I prefer the mains not to be modular. I read there is a power loss in modular connections. Maybe not a huge deal, but even so I prefer the mains not to be modular.

There is a basis for this concern. Both in theory and in practice.

The amount of the drop in voltage across the connection depends

upon the quality of the connector and it's lack of oxidation / corrosion.

In ideal conditions the drop in voltage across the connection is negligible.

Periodically breaking / remaking the connection will ameliorate the effects

of oxidation upon the connection.

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Guest Kojak

Well you're always going to use the mains of the psu, so why would you want it to be modular?

 

From a purist's point of view it matters.

As a practical concern it does not matter.

Electrical theory and reality are unaffected.

It's a matter of choice born of preference.

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From a purist's point of view it matters.

As a practical concern it does not matter.

Electrical theory and reality are unaffected.

It's a matter of choice born of preference.

 

Um yeah, not sure why one would want to add an extra break in the connection when it's not necessary or provide any benefit. :shrug:
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I still don't understand this single, or not rail.

 

Being retired for almost 20 years, now, things must of changed.

You have a PSU, it has an input, you have a transformer for 12V, and a

transformer for 3.3/5 volt. A bridge rect, to make is DC +/- for each.

 

Therefore you only have one rail, for 12v and one rail for 3.3/5 v.

 

If you have a PSU that says it has four rails, then it would have to have

four transformers. NOT

 

By the national codes, you can only have 25amps on any single 12v rail.

Open the transformer, all the 12v wires come from the same place, but in

theory can only handle 25amps.

Same on a multi rail or single rail PSU.

 

Its only an advertising/selling point.

 

At least thats what I seem to remember since starting in electonics in 1966.

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Guest Kojak

I still don't understand this single, or not rail.

 

Being retired for almost 20 years, now, things must of changed.

You have a PSU, it has an input, you have a transformer for 12V, and a

transformer for 3.3/5 volt. A bridge rect, to make is DC +/- for each.

 

Therefore you only have one rail, for 12v and one rail for 3.3/5 v.

 

If you have a PSU that says it has four rails, then it would have to have

four transformers. NOT

 

By the national codes, you can only have 25amps on any single 12v rail.

Open the transformer, all the 12v wires come from the same place, but in

theory can only handle 25amps.

Same on a multi rail or single rail PSU.

 

Its only an advertising/selling point.

 

At least thats what I seem to remember since starting in electronics in 1966.

 

This link should help you understand.

 

http://www.xbitlabs.com/articles/cases/dis...ethodology.html

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I have read that link. Its as full of bull as any other PSU manufacturer.

To have more then one rail, you have to have more then one xfmr.

 

I checked back, its only 20 amps per rail. Each must be set for that.

To achieve a higher rail, they put more then one wire to get the amperage.

 

They must follow national standards.

 

I'll see if I can find it. Then maybe you will understand it.

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Guest Kojak

I have read that link. Its as full of bull as any other PSU manufacturer.

To have more then one rail, you have to have more then one xfmr.

 

I checked back, its only 20 amps per rail. Each must be set for that.

To achieve a higher rail, they put more then one wire to get the amperage.

 

They must follow national standards.

 

I'll see if I can find it. Then maybe you will understand it.

 

I was trying to help. I'm not looking for an argument. Goodnight.

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I can't really say anything. What they are supposed to do, and what they do?

All I am saying, is that there is a 99.9% chance that what they say is a

multi rail, is really a single rail.

Both have their good points, and in theory a multi rail is best. But that

is with everything like is should be.

When I had my business, the servers were supplied with a multi rail, clean power,

PSU. It cost around 3 grand, and weighted about 300lbs, had a 50amp 240volt input.

Wouldn't fit in a home computer.

 

The build of each PSU in dependent on the manufacturer. The only way to check

for sure, is buy it, open it up, and test it.

 

You just have to go by user input, and hope you get a good one. If you read all

the stuff, PC&C was a good one. Lately they seem to have some issues, including

a few government agencies going after them.

 

Right now, by the user input I read, corsair seems to be one of the best.

 

Were all in the same boat, luck be with us.

 

As for that PSU, it doesn't have four rails, they have put four or more wires to a single rail.

They are supposed to be limited to 20amp (-8 %) each. Did they do that or not? Who knows?

Edited by RAH
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when the psu says multiple 12v rails, almost ALL the time, it's a single internal rail at max amps split into multiple rails of 20amps each using current limiters. big reason when building a high end system to stick to single rail so you don't have to load balance.

 

if it's a single rail, you still start off w/ a single 12v rail that splits into multiple rails with NO current limiters and no load balancing reqs.

 

if your total system uses 30 amps, then a 30 amp single rail would be fine, but you would have to get a 40 amp multirail psu since each "rail" will trip the over current if you go above 20 amps a rail.

 

the loophole is that there ARE a few rare psu that don't follow the 240VA limit, and there are a few that a TRUE multirail units, but thoose are excessively expensive and not used for the size of computers we usually build here at the pit.

 

so yes, in most pc psu there is only one main 12v feed for all psu. multirail psu just integrate current limiters as the official ATX12V design doesn't allow more than 240VA on a rail. (20 amps)

 

and the theory that a multirail psu is better comes from the fact that a multirail unit will split loads and lower the noise on each feed. most home pc parts are NOT that picky, and i don't believe it worth the hassle of having to load balance.

Edited by wdeydwondrer
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