PSU - bust the myth

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PSU - bust the myth

Postby Godlike » 2016-1-27 @ 16:13

I couldn't find similar topic so I decided to open one.
May new PSU damage older motherboard and other components?
For eg. Antec phantom 350 + socket 370 CUSL2-C. I know mobo is ATX12 version 1.x compliant and PSU 2.x. It can be ignored by 24pin to 20pin adapter easily.
Also, PSU doesn't support rails such as -5 ISA. Does +12 V rails has standards ? I should be aware of AC/DC amperes?
What is the most important part in using old mobo with new PSU and how ewentually can this be fixed. Regards
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Re: PSU - bust the myth

Postby alexanrs » 2016-1-27 @ 16:28

There are only two issues with using newer PSUs with older stuff:

1- Lack of -5V - this is mostly a non-issue for a gaming machine. Most sound cards don't use it (they use -12V), though I've heard some onboard sound solutions use it as well but I've never encountered any myself. It is very easy to add -5V with a voltage regulator deriving it from the -12V rail.

2- Wrong power distribution - New PSUs are designed for PCs that draw most of its power from the 12V rails, whereas most pre-P4/A64 computers drew most of their power from the 5V rails. This means that, where an old 350W PSU would provide enough power in the 5V rails for your old PSU, a new 350W one might not. And there are issues associated with getting a PSU that is too beefy to compensate - some powerful PSUs aren't very happy when you draw much from the 5V rails without drawing power from the 12V ones.
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Re: PSU - bust the myth

Postby luckybob » 2016-1-27 @ 19:43

^^^ basically true.

The majority of NEW power supply designs, they are designed to make +12. THEN they put in a dc/dc converter for the 5v and 3.3v. This means you can basically load it however you want to. A Pentium 3 wont stress a quality psu to any significant degree. A P4 will, but most of them are designed for high 12v loads.

moral of the story; get a quality unit, and forget about it.
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Re: PSU - bust the myth

Postby alexanrs » 2016-1-27 @ 20:23

luckybob wrote:moral of the story; get a quality unit, and forget about it.

Well, unless you are building a high end Athlon machine. Then you gotta be way more careful.
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Re: PSU - bust the myth

Postby 386SX » 2016-1-27 @ 20:33

alexanrs wrote:
luckybob wrote:moral of the story; get a quality unit, and forget about it.

Well, unless you are building a high end Athlon machine. Then you gotta be way more careful.

With an ATX2.3 600W good quality and heavy psu on an XP 3200+ and a Radeon 9000 in fact I had really really low 5V measured and I would say instability here and there (and shutdowns...). I don't know if it was using 5V from the 12V rail but I doubt it.
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Re: PSU - bust the myth

Postby luckybob » 2016-1-27 @ 23:04

What brand?
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Re: PSU - bust the myth

Postby Tetrium » 2016-1-27 @ 23:41

I think by these days, it would be easier to either source an old (but good quality) '5v-PSU' and recap it, or source a sA board that uses 12v (same P4 4-pin connector as the Pentium 4), though I'm not sure if all sA boards that actually have this connector, really use the 12v instead of the 5v

Iirc it was mostly the newer nForce boards that used 12v, I very rarely saw any VIA chipsetted sA board with this extra power connector
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Re: PSU - bust the myth

Postby Godlike » 2016-1-28 @ 16:22

ATX12V version 2.0 Compliance: The Phantom complies with the new ATX12V
version 2.0 standard. It features dual +12V outputs, a 24-pin Main Power
Connector, and a 4-pin 12V Power Connector to the motherboard. It also includes
five to seven 4-pin Peripheral Power Connectors, one to two 4-pin Floppy Drive
Power Connectors, two to four Serial ATA Power Connectors, a 6-pin PCI
Express connector and a 24-pin to 20-pin power cable adapter.
It's backwards compatible with previous ATX form factor power supplies. If
your motherboard has a 20-pin onboard connection, use the 24-pin to 20-pin
adapter that is included with Phantom. To make sure you connect your power
supply properly, please refer to the user manuals supplied with your motherboard
and peripherals before connecting Phantom to any of your devices.
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Re: PSU - bust the myth

Postby Godlike » 2016-1-28 @ 16:27

Manual says: ATX12V version 2.0 Compliance, backwards compatible (just to use it with adapter)

© Copyright 2004 Antec, Inc. All rights reserved.
Reproduction in whole or in part without written permissions is prohibited. Printed in China.
Version 1.0.5 07/16/04

This is about Antec Phantom 350Watt from 2004 if I'm right.
What do you all think, this psu will damage mobo in long-term use with CUSL2-C or not ?
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Re: PSU - bust the myth

Postby Godlike » 2016-1-28 @ 16:58

Take a look at this: https://en.wikipedia.org/wiki/Power_sup ... _(computer)#ATX12V_standard

alexanrs wrote:There are only two issues with using newer PSUs with older stuff:

1- Lack of -5V - this is mostly a non-issue for a gaming machine. Most sound cards don't use it (they use -12V), though I've heard some onboard sound solutions use it as well but I've never encountered any myself. It is very easy to add -5V with a voltage regulator deriving it from the -12V rail.

2- Wrong power distribution - New PSUs are designed for PCs that draw most of its power from the 12V rails, whereas most pre-P4/A64 computers drew most of their power from the 5V rails. This means that, where an old 350W PSU would provide enough power in the 5V rails for your old PSU, a new 350W one might not. And there are issues associated with getting a PSU that is too beefy to compensate - some powerful PSUs aren't very happy when you draw much from the 5V rails without drawing power from the 12V ones.


If: "It is very easy to add -5V with a voltage regulator deriving it from the -12V rail" then why not to 12v rails convert to 5v in second point
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Re: PSU - bust the myth

Postby nforce4max » 2016-1-28 @ 20:44

Godlike wrote:Take a look at this: https://en.wikipedia.org/wiki/Power_sup ... _(computer)#ATX12V_standard

alexanrs wrote:There are only two issues with using newer PSUs with older stuff:

1- Lack of -5V - this is mostly a non-issue for a gaming machine. Most sound cards don't use it (they use -12V), though I've heard some onboard sound solutions use it as well but I've never encountered any myself. It is very easy to add -5V with a voltage regulator deriving it from the -12V rail.

2- Wrong power distribution - New PSUs are designed for PCs that draw most of its power from the 12V rails, whereas most pre-P4/A64 computers drew most of their power from the 5V rails. This means that, where an old 350W PSU would provide enough power in the 5V rails for your old PSU, a new 350W one might not. And there are issues associated with getting a PSU that is too beefy to compensate - some powerful PSUs aren't very happy when you draw much from the 5V rails without drawing power from the 12V ones.


If: "It is very easy to add -5V with a voltage regulator deriving it from the -12V rail" then why not to 12v rails convert to 5v in second point


It is easier to just not bother and source an older but well known high quality unit. You don't see people going out of their way to do this not when you can just spent $15-25 and get something that is ready to go without paying $50-75 for a modern unit. Most of us here already know what excrement off brand units to avoid anyway....
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Re: PSU - bust the myth

Postby TELVM » 2016-1-28 @ 21:08

alexanrs wrote:There are only two issues with using newer PSUs with older stuff:

1- Lack of -5V - this is mostly a non-issue for a gaming machine. Most sound cards don't use it (they use -12V), though I've heard some onboard sound solutions use it as well but I've never encountered any myself. It is very easy to add -5V with a voltage regulator deriving it from the -12V rail.

2- Wrong power distribution - New PSUs are designed for PCs that draw most of its power from the 12V rails, whereas most pre-P4/A64 computers drew most of their power from the 5V rails. This means that, where an old 350W PSU would provide enough power in the 5V rails for your old PSU, a new 350W one might not. And there are issues associated with getting a PSU that is too beefy to compensate - some powerful PSUs aren't very happy when you draw much from the 5V rails without drawing power from the 12V ones.


^ This.

If your PIII system doesn't need -5V (probable) a PSU like the Antec Phantom 350 with a 30A +5V rail will be plenty enough, overkill in fact.

HOWEVER be advised that the Phantoms (like other Antecs of that time) were stuffed full of Fuhjyyu crapacitors, amongst the worst and less reliable junk ever laid inside a PSU, which after more than a decade shouldn't be relied upon (to put it softly).

Antec Phantom 500 ruined by Fuhjyyu crapacitors
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Re: PSU - bust the myth

Postby PCBONEZ » 2016-1-28 @ 22:57

Godlike wrote:If: "It is very easy to add -5V with a voltage regulator deriving it from the -12V rail" then why not to 12v rails convert to 5v in second point


You can. They even make them.
http://www.ebay.com/sch/i.html?_odkw=DC ... c&_sacat=0
I would choose one with respectably sized electrolytics on it (or solid polymer) and check it's ripple OP before using it in a PC.
Might need to add additional filtering or to switch to lower ESR caps.
.
Last edited by PCBONEZ on 2016-1-29 @ 23:17, edited 4 times in total.
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Re: PSU - bust the myth

Postby PCBONEZ » 2016-1-28 @ 23:43

TELVM wrote:HOWEVER be advised that the Phantoms (like other Antecs of that time) were stuffed full of Fuhjyyu crapacitors, amongst the worst and less reliable junk ever laid inside a PSU, which after more than a decade shouldn't be relied upon (to put it softly).

Antec Phantom 500 ruined by Fuhjyyu crapacitors

All the Antec Smart-(whatever) and True-(whatever) models were loaded with Fuhjyyu.
Others were too. Just don't recall them.
.
These are old pics I took 5-10 years ago.
TP2-550.jpg

TP2-550EPS12V_.jpg

.
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Re: PSU - bust the myth

Postby alexanrs » 2016-1-29 @ 00:45

Just beware that deriving -5V from -12V is feasible because nothing draws much from it. Odds are even a new PSU design is much more capable at providing 5V than any cheap buck down converter out there, and there are issues about using one of those in parallel with another power source.
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Re: PSU - bust the myth

Postby gdjacobs » 2016-1-29 @ 01:55

alexanrs wrote:Just beware that deriving -5V from -12V is feasible because nothing draws much from it. Odds are even a new PSU design is much more capable at providing 5V than any cheap buck down converter out there, and there are issues about using one of those in parallel with another power source.


Most new power supplies derive their minor rails from the 12V rail via buck converters. You're right about parallel voltage supplies, though. There are all kinds of different methods to parallel, but likely the easiest I can think of would be to use diodes (to avoid sinking current if a converter fails short) and ballasting resistors. Hopefully both converters also have proper overcurrent protection so the smoke doesn't get out.
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Re: PSU - bust the myth

Postby Godlike » 2016-1-29 @ 09:02

nforce4max wrote:
Godlike wrote:Take a look at this: https://en.wikipedia.org/wiki/Power_sup ... _(computer)#ATX12V_standard

alexanrs wrote:There are only two issues with using newer PSUs with older stuff:

1- Lack of -5V - this is mostly a non-issue for a gaming machine. Most sound cards don't use it (they use -12V), though I've heard some onboard sound solutions use it as well but I've never encountered any myself. It is very easy to add -5V with a voltage regulator deriving it from the -12V rail.

2- Wrong power distribution - New PSUs are designed for PCs that draw most of its power from the 12V rails, whereas most pre-P4/A64 computers drew most of their power from the 5V rails. This means that, where an old 350W PSU would provide enough power in the 5V rails for your old PSU, a new 350W one might not. And there are issues associated with getting a PSU that is too beefy to compensate - some powerful PSUs aren't very happy when you draw much from the 5V rails without drawing power from the 12V ones.


If: "It is very easy to add -5V with a voltage regulator deriving it from the -12V rail" then why not to 12v rails convert to 5v in second point


It is easier to just not bother and source an older but well known high quality unit. You don't see people going out of their way to do this not when you can just spent $15-25 and get something that is ready to go without paying $50-75 for a modern unit. Most of us here already know what excrement off brand units to avoid anyway....


As you know PSU is the most important part in PC. Of course is more difficult to get NEW older high quality unit than getting newer PSU. People don't want to damage thier high quality builds and rare stuff in it with older but used PSU so that's why this tread has opened, to find compromise solutions or eventually modify new psu's to work with golden era standards. I think PSU threads is right on the place. Distributing right electricity to components could be really important for stability. PC's withot power are nothing really...like a car without gasoline. Apart from that what brand you recommend ?
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Re: PSU - bust the myth

Postby Godlike » 2016-1-29 @ 09:09

TELVM wrote:If your PIII system doesn't need -5V (probable) a PSU like the Antec Phantom 350 with a 30A +5V rail will be plenty enough, overkill in fact.

HOWEVER be advised that the Phantoms (like other Antecs of that time) were stuffed full of Fuhjyyu crapacitors, amongst the worst and less reliable junk ever laid inside a PSU, which after more than a decade shouldn't be relied upon (to put it softly).

Antec Phantom 500 ruined by Fuhjyyu crapacitors


PIII CUSL2-C don't need -5V, don't have ISA eighter. PSU has to powered a lot of stull in PC. Cards, ATX full tower full of drives, watercooling, chassis fans etc.
Thans for reminding about caps. Regards
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Re: PSU - bust the myth

Postby Kreshna Aryaguna Nurzaman » 2016-1-29 @ 09:26

luckybob wrote:^^^ basically true.

The majority of NEW power supply designs, they are designed to make +12. THEN they put in a dc/dc converter for the 5v and 3.3v. This means you can basically load it however you want to. A Pentium 3 wont stress a quality psu to any significant degree. A P4 will, but most of them are designed for high 12v loads.

moral of the story; get a quality unit, and forget about it.

Then I imagine a 700 watt Thermaltake TR2 700 should be enough for the following system:

Intel 440BX
Pentium III 600
Voodoo5 5500 AGP
Voodoo Graphics
Diamond MonsterSound 3D
Sound Blaster AWE 64 Gold
Thrustmaster ACM Game Card
Yamaha SW60 XG

Yup, basically it has one AGP card, two PCI cards, and three ISA cards. A modern 700 watt PSU should be enough, no? The TR2 has 24A from its +5V.
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Re: PSU - bust the myth

Postby RacoonRider » 2016-1-29 @ 09:52

Tetrium wrote: I'm not sure if all sA boards that actually have this connector, really use the 12v instead of the 5v


You're correct, for my Socket A machine a 18A 5V rail was not enough despite the 4-pin 12V connector (Ga-7n400s mobo).

The symptoms I experienced with PSU not being enough for the systems were random hangs and reboots, even at idle state. Changing the videocard might give you a clue, when I swapped the hungry 9800Pro to an effecient 9600Pro, it cured the issue.
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