VOGONS


PSU for Socket A - Athlon XP 3000+

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First post, by Valentyn

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Hi folks,

I've been digging about trying to find a decent PSU with good 5V rail for build I'm planning.

Motherboard: Epox 8K5A3+ with an Athlon 3000+

I'll be running 3DFX cards 5500, and others upto the FX 5950 Ultra.

Having looked online I see a lot of newer power supplies actually have pretty weak 5V rails, since modern motherboards mostly use the 12V.

The only Powersupply I've found so far that seems to have an okay 3.3v + 5V rail is the BeQuiet PurePower 11 700W
It has a combined 3.3v + 5V of 150W. The cheaper, and lower end version drop wattage in those rails pretty quickly.

Although it feels kind of silly spending so much on a 700W to run a Windows 98, and XP system.

Does anyone have any other recommendations that they would suggest?

Reply 1 of 36, by Joseph_Joestar

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Don't just look at the watts, check how many amps are on the 5V rail. You want at least 30A there for high-end AthlonXP CPUs.

I ended up getting a used LC Power branded PSU from the early 2000s for mine, and it has served me well so far *knock on wood*.

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Reply 2 of 36, by The Serpent Rider

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You want at least 30A there for high-end AthlonXP CPUs.

That's a common myth. You don't need that much current. Modern PSU with 25A should more that enough.

Last edited by The Serpent Rider on 2020-10-17, 18:50. Edited 1 time in total.

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Reply 3 of 36, by Valentyn

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Joseph_Joestar wrote on 2020-10-17, 18:46:

Don't just look at the watts, check how many amps are on the 5V rail. You want at least 30A there for high-end AthlonXP CPUs.

I ended up getting a used LC Power branded PSU from the early 2000s for mine, and it has served me well so far *knock on wood*.

That's what i've been doing. It's rather hard to find ones with a decent 5v Ampagere and voltage.

That be quiet has 20A on the 5V.

I'll have to keep digging.

Reply 4 of 36, by Joseph_Joestar

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The Serpent Rider wrote on 2020-10-17, 18:48:

That's a common myth. You don't need that much current. Modern PSU with 25A should more that enough.

If I remember correctly, it's based on AMDs own tech specs for the AthlonXP CPU.

Here's a contemporary forum thread discussing the issue, but I don't have the tech specs on hand.

PC#1: Pentium MMX 166 / Soyo SY-5BT / S3 Trio64V+ / Voodoo1 / OPTi 82C930 / AWE64
PC#2: Celeron 466 / Abit ZM6 / Voodoo3 / AWE64 Gold / YMF744 / SC-155
PC#3: AthlonXP 1700+ / Abit KT7A / GeForce4 / SBLive / ALS100
PC#4: Athlon64 3700+ / DFI LanParty / 9600GT / X-Fi Titanium

Reply 5 of 36, by The Serpent Rider

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It was already discussed here on Vogons multiple times. Even dual CPU systems don't pull that much power.

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Reply 6 of 36, by Valentyn

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The Serpent Rider wrote on 2020-10-17, 18:48:

You want at least 30A there for high-end AthlonXP CPUs.

That's a common myth. You don't need that much current. Modern PSU with 25A should more that enough.

I have a Silverstone SST-ST60F-SG, and it states 5v 25A, with a combined 3.3v + 5v of 140W.

Think this will do the job? It's a small form factor one, might need to get some SATA to molex power adapters, as it only has a single molex.

Keep in mind the motherboard doesn't have a 4pin power, just the ATX power connector.

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Reply 9 of 36, by Joseph_Joestar

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Found the AthlonXP datasheet.

On page 22 the electrical specifications of the CPU are listed, and they do suggest 30A or more is needed. It's possible that some modern PSUs can handle this better nowadays, but it was no myth back in the day.

PC#1: Pentium MMX 166 / Soyo SY-5BT / S3 Trio64V+ / Voodoo1 / OPTi 82C930 / AWE64
PC#2: Celeron 466 / Abit ZM6 / Voodoo3 / AWE64 Gold / YMF744 / SC-155
PC#3: AthlonXP 1700+ / Abit KT7A / GeForce4 / SBLive / ALS100
PC#4: Athlon64 3700+ / DFI LanParty / 9600GT / X-Fi Titanium

Reply 10 of 36, by The Serpent Rider

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On page 22 the electrical specifications of the CPU are listed, and they do suggest 30A

1.65v current =/= 5v current.

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Reply 11 of 36, by ohhwell

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Joseph_Joestar wrote on 2020-10-17, 18:46:

Don't just look at the watts, check how many amps are on the 5V rail. You want at least 30A there for high-end AthlonXP CPUs.

I ended up getting a used LC Power branded PSU from the early 2000s for mine, and it has served me well so far *knock on wood*.

You see, you actually should be looking at watts if you don't know what you are doing. If you had then you would have realized that the 1.65v at the max draw of 41.4 A is indeed the 68.3 W TDP they list for the 2600+ in the spec sheet you listed. Getting that wattage from a 5v rail would simply be 68.3/5 which is.... 13.662 Amps (15.7 assuming 15% efficiency loss in conversion from 5v) so yes, a PSU with a 25A 5V rail is plenty.

I know this thread is a little old at this point but it was the first result when I google searched and yes, The Serpent Rider already pointed out your error, I thought it would be good to expand on it a little for posterity.

Comparing Watts to Watts is the best way.

Reply 12 of 36, by Tetrium

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The Serpent Rider wrote on 2020-10-17, 18:54:

It was already discussed here on Vogons multiple times. Even dual CPU systems don't pull that much power.

You sure 2x Athlon XP (which can have a max power dissipation of up to nearly 80W) will run on 25A on the 5v rail?

I don't know where this has been discussed though, a few links would be appreciated.

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Reply 13 of 36, by LubieCipy

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I thought Pentium III platforms mostly use the 3.3 / 5V line. In turn, newer designs, such as AthlonXP and Pentium 4, used the 12V line. Was I wrong? 😀

Reply 14 of 36, by Tetrium

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Joseph_Joestar wrote on 2020-10-17, 19:10:

Found the AthlonXP datasheet.

On page 22 the electrical specifications of the CPU are listed, and they do suggest 30A or more is needed. It's possible that some modern PSUs can handle this better nowadays, but it was no myth back in the day.

PSUs from back then weren't as good as the PSUs we have these days.
My guess is that these specs were at least partially made this way by AMD to have plenty of leeway in case it were to come to hardware getting damaged because of Athlon XP power draw.

Back in the day I would however prefer to use 30A in case a higher power usage Athlon (be it Thunderbird or XP) was used.

And one issue of todays PSUs is that they heavily favor supplying power on the 12v lines. Some supplies *may* find it difficult to provide stable output in case the 12v was sparsely used while the 5v had significant power draw.

Personally I'd probably check it on a PSU to PSU basis these days. But back then I preferred to use at least 30A.

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Reply 15 of 36, by Tetrium

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LubieCipy wrote on 2021-11-19, 17:14:

I thought Pentium III platforms mostly use the 3.3 / 5V line. In turn, newer designs, such as AthlonXP and Pentium 4, used the 12V line. Was I wrong? 😀

sA typically continues the heavy use of 5v. Pentium 4 and Athlon64 were the 1st CPUs of their respective lines to rely on 12v instead of 5v.
This is kinda unfortunate regarding the Athlon XPs and Athlon Thunderbirds. Pentium 3 had way lower TDP so this isn't as much of an issue these days.

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Reply 16 of 36, by Joseph_Joestar

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ohhwell wrote on 2021-11-19, 16:50:

I know this thread is a little old at this point but it was the first result when I google searched and yes, The Serpent Rider already pointed out your error, I thought it would be good to expand on it a little for posterity.

Comparing Watts to Watts is the best way.

Cheers, and thanks for the clarification!

Good to know in case I need to get a new for PSUs for my AthlonXP system at some point in the future.

PC#1: Pentium MMX 166 / Soyo SY-5BT / S3 Trio64V+ / Voodoo1 / OPTi 82C930 / AWE64
PC#2: Celeron 466 / Abit ZM6 / Voodoo3 / AWE64 Gold / YMF744 / SC-155
PC#3: AthlonXP 1700+ / Abit KT7A / GeForce4 / SBLive / ALS100
PC#4: Athlon64 3700+ / DFI LanParty / 9600GT / X-Fi Titanium

Reply 17 of 36, by cyclone3d

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The thing about the recommended PSU specs is that the mfgs have to put in a way higher number than is actually needed, especially back then as you would have PSUs being sold as double or more of what they could actually handle.

Put the load on them they claim to be able to do and you would end up with fire or smoke.

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Reply 18 of 36, by kdr

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Tetrium wrote on 2021-11-19, 17:17:

And one issue of todays PSUs is that they heavily favor supplying power on the 12v lines. Some supplies *may* find it difficult to provide stable output in case the 12v was sparsely used while the 5v had significant power draw.

Yep, I have an Athlon XP 2400+ system that I'm building and the (admittedly rather crappy) 320W ATX PSU that I'm using with it right now is only rated for 125W on the 3.3V/5V rails. As a result the actual voltages it's producing are 3.13V, 4.73V, and 12.76V -- yikes! It seems to me that this particular PSU isn't well regulated unless there is significant load on the 12V rail. So I'm currently searching for a more suitable PSU for this build. I think the presence of a -5V rail is a good indicator of a supply's "vintageness". (Wonder around what year the -5V started to disappear?)

Reply 19 of 36, by The Serpent Rider

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Tetrium wrote:

You sure 2x Athlon XP (which can have a max power dissipation of up to nearly 80W) will run on 25A on the 5v rail?

From what I've seen, almost all, if not all dual Socket A mobos use additional connectors, which most likely 12v rail. So realistically - dual Tualatin setup is maximum what you can power from 5v rail via standard ATX plug. There're also limits to what ATX connector could take, before quite literally starting to melt.

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