Horun wrote on 2024-02-08, 02:59:

Not easy to measure the total current on four +5 on a ATX with one meter.... I know you can pull a pin out and check, that would give a good average per leg and should be same on all 4. so 4x meter.....
Be a bit tough to pull all 4 to meter and back to 4... most Digi's have a 10amp max for like 15 seconds max (or some such thing) or at least mine does on the high current range.....

I'm interested in a measurement of the voltage drop of the PSUs +5V rail, while the PC is at high load.
Not the amperage draw.

That should give us an estimation of how close the PSU is to "running out of steam" so to speak 😀

B24Fox wrote on 2024-02-08, 03:25:

I'm interested in a measurement of the voltage drop of the PSUs +5V rail, while the PC is at high load. Not the amperage draw. […]
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Horun wrote on 2024-02-08, 02:59:

Not easy to measure the total current on four +5 on a ATX with one meter.... I know you can pull a pin out and check, that would give a good average per leg and should be same on all 4. so 4x meter.....
Be a bit tough to pull all 4 to meter and back to 4... most Digi's have a 10amp max for like 15 seconds max (or some such thing) or at least mine does on the high current range.....

I'm interested in a measurement of the voltage drop of the PSUs +5V rail, while the PC is at high load.
Not the amperage draw.

That should give us an estimation of how close the PSU is to "running out of steam" so to speak 😀

True But a good supply with Under Voltage and Over Current will stay within spec then just shut down if under/over the limits...

Horun wrote on 2024-02-08, 03:49:

B24Fox wrote on 2024-02-08, 03:25:

I'm interested in a measurement of the voltage drop of the PSUs +5V rail, while the PC is at high load. Not the amperage draw. […]
Show full quote

Horun wrote on 2024-02-08, 02:59:

Not easy to measure the total current on four +5 on a ATX with one meter.... I know you can pull a pin out and check, that would give a good average per leg and should be same on all 4. so 4x meter.....
Be a bit tough to pull all 4 to meter and back to 4... most Digi's have a 10amp max for like 15 seconds max (or some such thing) or at least mine does on the high current range.....

I'm interested in a measurement of the voltage drop of the PSUs +5V rail, while the PC is at high load.
Not the amperage draw.

That should give us an estimation of how close the PSU is to "running out of steam" so to speak 😀

True But a good supply with Under Voltage and Over Current will stay within spec then just shut down if under/over the limits...

If the +5V rail goes down to 4.6V and the Mobo or HDD starts corrupting data; then I would rather it shut down...

For me, If it dips under 4.85V, it's a no-go. It could be made out of gold for all I care; i'm not using it 😀

Ideally, anything under 4.9V should raise serious concern
(10% vDrop)

I get that you're basically talking about that if you have a VERY stable curent, just above the problematic threshold; then in theory you're fine.
But you only get that with pretty expensive PSUs... not with these El Cheap-o "good enough" types that you wanna buy 10 of 'em to fill all your retro rigs with...

I can't measure that but don't look too far either. My Athlon MPs have a TDP of 50W, 60W max. So worst case is 120W and the mainboard also has an additional 12V connector to help. I tried, it runs stable even without the 12V connector.

5x 27 = 135W, I doubt that on ANY single-CPU system this should be a problem. The worst Athlon XPs are at 75W.

Minutemanqvs wrote on 2024-02-08, 06:44:

I can't measure that but don't look too far either. My Athlon MPs have a TDP of 50W, 60W max. So worst case is 120W and the mainboard also has an additional 12V connector to help. I tried, it runs stable even without the 12V connector.

5x 27 = 135W, I doubt that on ANY single-CPU system this should be a problem. The worst Athlon XPs are at 75W.

Yes, but also don't forget that from the +5V rail, depending on the models:
One SATA SSD can pull up to 2A = > 10W
One CDrom drive , up to 2A = > 10W
One HDD can pull up to 1A => 5W
One FDD, up to 1A =>5W
So just having 2 storage drives connected, copying a CD, and reading a floppy, can pull up to 30W from +5V.

Not to mention video cards (2x Voodoo 2 in SLI + GeForce2, anyone??), sound cards, and the actual motherboard...

If you read @bloodem's posts a few pages back , the Segotep i mentioned, which states 30A!! for +5V , is at it's limits (4.7V) on his AthlonXP system, and also on my 2000+ Palomino it's pretty much at it's limit too!

So in regards to cheap PSUs; you always have to choose something that states way more than what you think u need.

And a multimeter check on the +5v (on any connector that is closest to the PSU) while EVERYTHING is running, is a must, IMO.
It's the easiest way to find out if the PSU is struggling on that system.

B24Fox wrote on 2024-02-08, 23:27:

Yes, but also don't forget that from the +5V rail, depending on the models: One SATA SSD can pull up to 2A = > 10W One CDrom dr […]
Show full quote

Minutemanqvs wrote on 2024-02-08, 06:44:

I can't measure that but don't look too far either. My Athlon MPs have a TDP of 50W, 60W max. So worst case is 120W and the mainboard also has an additional 12V connector to help. I tried, it runs stable even without the 12V connector.

5x 27 = 135W, I doubt that on ANY single-CPU system this should be a problem. The worst Athlon XPs are at 75W.

Yes, but also don't forget that from the +5V rail, depending on the models:
One SATA SSD can pull up to 2A = > 10W
One CDrom drive , up to 2A = > 10W
One HDD can pull up to 1A => 5W
One FDD, up to 1A =>5W
So just having 2 storage drives connected, copying a CD, and reading a floppy, can pull up to 30W from +5V.

Not to mention video cards (2x Voodoo 2 in SLI + GeForce2, anyone??), sound cards, and the actual motherboard...

If you read @bloodem's posts a few pages back , the Segotep i mentioned, which states 30A!! for +5V , is at it's limits (4.7V) on his AthlonXP system, and also on my 2000+ Palomino it's pretty much at it's limit too!

So in regards to cheap PSUs; you always have to choose something that states way more than what you think u need.

And a multimeter check on the +5v (on any connector that is closest to the PSU) while EVERYTHING is running, is a must, IMO.
It's the easiest way to find out if the PSU is struggling on that system.

4.97V on the 5V rail
11.87V on the 12V rail

That is wit the whole system consuming 210W at the plug and under full load.

Some tip for psu for retro build (PIII-S,P4,A64,3dfx,V3/V5,ATI,1950,NV,FX,690,..)?

Whenever it was possible I always used a Seasonic as power supply in my systems.

For example now I have in my daily driver as psu Seasonic PRIME TX 1600W ATX3.0 SSR-1600TR2 and I love it.

But in my country is oldest new Seasonic psu Seasonic SSP-400ET2 (400W) 500ET2(500W) 600ET2 (600W), Seasonic G12 GC,..

I would like to buy some quality so that I don't fear about my "old" new hardware.

JosefHrib wrote on 2024-02-21, 23:17:

Some tip for psu for retro build (PIII-S,P4,A64,3dfx,V3/V5,ATI,1950,NV,FX,690,..)? […]
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Some tip for psu for retro build (PIII-S,P4,A64,3dfx,V3/V5,ATI,1950,NV,FX,690,..)?

Whenever it was possible I always used a Seasonic as power supply in my systems.

For example now I have in my daily driver as psu Seasonic PRIME TX 1600W ATX3.0 SSR-1600TR2 and I love it.

But in my country is oldest new Seasonic psu Seasonic SSP-400ET2 (400W) 500ET2(500W) 600ET2 (600W), Seasonic G12 GC,..

I would like to buy some quality so that I don't fear about my "old" new hardware.

Nice PSU ! my problem is: would never spend $500 to power a build maybe only worth $500 at best. Some may think their high power athlon is worth gold but not in my area 😀

So I bought for my retro build Seasonic PSU too. I had many PSUs from Seasonic for for last around twenty years and zero problem, so why trying something other. For retro build I have prepared Seasonic PRIME TX-850 Titanium 850W. 😀

Minutemanqvs wrote on 2024-02-09, 19:07:

4.97V on the 5V rail 11.87V on the 12V rail […]
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B24Fox wrote on 2024-02-08, 23:27:

Yes, but also don't forget that from the +5V rail, depending on the models: One SATA SSD can pull up to 2A = > 10W One CDrom dr […]
Show full quote

Minutemanqvs wrote on 2024-02-08, 06:44:

I can't measure that but don't look too far either. My Athlon MPs have a TDP of 50W, 60W max. So worst case is 120W and the mainboard also has an additional 12V connector to help. I tried, it runs stable even without the 12V connector.

5x 27 = 135W, I doubt that on ANY single-CPU system this should be a problem. The worst Athlon XPs are at 75W.

Yes, but also don't forget that from the +5V rail, depending on the models:
One SATA SSD can pull up to 2A = > 10W
One CDrom drive , up to 2A = > 10W
One HDD can pull up to 1A => 5W
One FDD, up to 1A =>5W
So just having 2 storage drives connected, copying a CD, and reading a floppy, can pull up to 30W from +5V.

Not to mention video cards (2x Voodoo 2 in SLI + GeForce2, anyone??), sound cards, and the actual motherboard...

If you read @bloodem's posts a few pages back , the Segotep i mentioned, which states 30A!! for +5V , is at it's limits (4.7V) on his AthlonXP system, and also on my 2000+ Palomino it's pretty much at it's limit too!

So in regards to cheap PSUs; you always have to choose something that states way more than what you think u need.

And a multimeter check on the +5v (on any connector that is closest to the PSU) while EVERYTHING is running, is a must, IMO.
It's the easiest way to find out if the PSU is struggling on that system.

4.97V on the 5V rail
11.87V on the 12V rail

That is wit the whole system consuming 210W at the plug and under full load.

Thank you Minutemanqvs.
It seems the LC6560GP3 v2.3 fairs very good for it's price!

As a thought: it may be that the 12V value is kind of low, because the PSU, internally has split power rails for 12V (+12V1 & +12V2).
And maybe your PC is wired to pull all it's 12V needs from only one of them.
Like, if the PSU has only the GPU power cable coming out of that 2nd rail; than that internal rail would remain completely unused.

I'm curious if anyone knows if it would be ok to short/merge together the two 12V rails.. *ahem* @Horun ??

L.E.
@Minutemanqvs
Are your LC6560GP3 v2.3 PSUs 80+ Silver? or 80+ Bronze?

B24Fox wrote on 2024-03-06, 20:47:

I'm curious if anyone knows if it would be ok to short/merge together the two 12V rails..

In general it's rather non-ideal to connect directly in parallel 2 constant-voltage power sources that aren't "perfectly" matched (see Nextys AN004 by Marco Geri)…

…but you might get away with it, because:

1. "Rather non-ideal" is a few levels better than "impossible" 😀
2. This dual-rail design was just to pander to the letter of the ATX standard saying, iirc, max 200W per line to try to mitigate imperfect shorts
3. Many "consumer" (cheapass) PSUs realized that in practice the separation was not implementable in practice not knowing what loads would be connected where (and indeed I've only seen the stock Dell ones having clearly marked yellow vs white wires for that), so they just fake it - that site with a nice explaination of the various AGP voltage and speed compatibilities has an article on this too!

My Seasonic SS-650KM has worked well with my 8KRA2+, but even with a 25A +5 I had to back down on my overclock of my XP-M 2600+. A little over 2.3 GHz, it began randomly restarting. I backed down to exactly 2.3 GHz, and no more restarts, but the +5 drops down to 4.70 under load per Motherboard Monitor.

Many years ago I read a post on Overclockers.com where an overclocked 8K3A+ melted the ATX power connector!

Ryccardo wrote on 2024-03-08, 14:22:

In general it's rather non-ideal to connect directly in parallel 2 constant-voltage power sources that aren't "perfectly" matche […]
Show full quote

B24Fox wrote on 2024-03-06, 20:47:

I'm curious if anyone knows if it would be ok to short/merge together the two 12V rails..

In general it's rather non-ideal to connect directly in parallel 2 constant-voltage power sources that aren't "perfectly" matched (see Nextys AN004 by Marco Geri)…

…but you might get away with it, because:

1. "Rather non-ideal" is a few levels better than "impossible" 😀
2. This dual-rail design was just to pander to the letter of the ATX standard saying, iirc, max 200W per line to try to mitigate imperfect shorts
3. Many "consumer" (cheapass) PSUs realized that in practice the separation was not implementable in practice not knowing what loads would be connected where (and indeed I've only seen the stock Dell ones having clearly marked yellow vs white wires for that), so they just fake it - that site with a nice explaination of the various AGP voltage and speed compatibilities has an article on this too!

Thank you! 👍 😁

If you look at some ATX PSU schematics you will see that the dual +12v rails come off the same +12v transformer lines. So combining them should not be a problem in general, though not sure why you would....
The better ones have some added inductors and capacitors to help the split rails but they are still from same side/windings of the tranny
examples: https://danyk.cz/s_atx06g.png and https://danyk.cz/s_atx06f.png
what Marco Geri is talking about is using two seperate PSU and running parallel which is different than combing output from same psu... just mho

B24Fox wrote on 2024-03-06, 20:47:

Thank you Minutemanqvs. It seems the LC6560GP3 v2.3 fairs very good for it's price! […]
Show full quote

Minutemanqvs wrote on 2024-02-09, 19:07:

4.97V on the 5V rail 11.87V on the 12V rail […]
Show full quote

B24Fox wrote on 2024-02-08, 23:27:

Yes, but also don't forget that from the +5V rail, depending on the models: One SATA SSD can pull up to 2A = > 10W One CDrom dr […]
Show full quote

Yes, but also don't forget that from the +5V rail, depending on the models:
One SATA SSD can pull up to 2A = > 10W
One CDrom drive , up to 2A = > 10W
One HDD can pull up to 1A => 5W
One FDD, up to 1A =>5W
So just having 2 storage drives connected, copying a CD, and reading a floppy, can pull up to 30W from +5V.

Not to mention video cards (2x Voodoo 2 in SLI + GeForce2, anyone??), sound cards, and the actual motherboard...

If you read @bloodem's posts a few pages back , the Segotep i mentioned, which states 30A!! for +5V , is at it's limits (4.7V) on his AthlonXP system, and also on my 2000+ Palomino it's pretty much at it's limit too!

So in regards to cheap PSUs; you always have to choose something that states way more than what you think u need.

And a multimeter check on the +5v (on any connector that is closest to the PSU) while EVERYTHING is running, is a must, IMO.
It's the easiest way to find out if the PSU is struggling on that system.

4.97V on the 5V rail
11.87V on the 12V rail

That is wit the whole system consuming 210W at the plug and under full load.

Thank you Minutemanqvs.
It seems the LC6560GP3 v2.3 fairs very good for it's price!

As a thought: it may be that the 12V value is kind of low, because the PSU, internally has split power rails for 12V (+12V1 & +12V2).
And maybe your PC is wired to pull all it's 12V needs from only one of them.
Like, if the PSU has only the GPU power cable coming out of that 2nd rail; than that internal rail would remain completely unused.

I'm curious if anyone knows if it would be ok to short/merge together the two 12V rails.. *ahem* @Horun ??

L.E.
@Minutemanqvs
Are your LC6560GP3 v2.3 PSUs 80+ Silver? or 80+ Bronze?

I have a 80+ Silver.

B24Fox wrote on 2024-03-06, 20:47:

I'm curious if anyone knows if it would be ok to short/merge together the two 12V rails.. *ahem* @Horun ??

Even in an ideal case scenario this could result in a current draw that the single 12V rail cables were not meant to handle, ie. fire hazard.

The reason I asked about combining +12V1 & +12V2, was because in the case of @Minutemanqvs' LC6560GP3 v2.3 PSUs 80+ Silver PSU (which specifies 2 split 12V rails on the label) ; the 12V is kinda low.
And that may be because on one of the +12V rails, only the GPU connector harness might be internally attached.... thus in the case of a retro PC which may not use it, that rail may sit idle (??).. while the PC's entire 12V load is on the other rail.

The way I would connect together both rails, would be internally, before all the harnesses/cabling.
And also replace the entire SATA and GPU harnesses, with molex ones, got from other/dead PSUs (so as to not put too much electrical stress on just one set of cables).

B24Fox wrote on 2024-03-15, 14:52:

The reason I asked about combining +12V1 & +12V2, was because in the case of @Minutemanqvs' LC6560GP3 v2.3 PSUs 80+ Silver PSU (which specifies 2 split 12V rails on the label) ; the 12V is kinda low.
And that may be because on one of the +12V rails, only the GPU connector harness might be internally attached.... thus in the case of a retro PC which may not use it, that rail may sit idle (??).. while the PC's entire 12V load is on the other rail.

11.87V is perfectly fine for the 12V line, it's within a 1.1% margin which is well within the ATX spec for that rail (+/- 5%), especially for an older system. I wouldn't worry about it, and as mentioned above merging both 12V rails would be an unnecessary risk for something that provides no benefits at all in this case.

TheMobRules wrote on 2024-03-15, 15:53:

B24Fox wrote on 2024-03-15, 14:52:

The reason I asked about combining +12V1 & +12V2, was because in the case of @Minutemanqvs' LC6560GP3 v2.3 PSUs 80+ Silver PSU (which specifies 2 split 12V rails on the label) ; the 12V is kinda low.
And that may be because on one of the +12V rails, only the GPU connector harness might be internally attached.... thus in the case of a retro PC which may not use it, that rail may sit idle (??).. while the PC's entire 12V load is on the other rail.

11.87V is perfectly fine for the 12V line, it's within a 1.1% margin which is well within the ATX spec for that rail (+/- 5%), especially for an older system. I wouldn't worry about it, and as mentioned above merging both 12V rails would be an unnecessary risk for something that provides no benefits at all in this case.

but what if, say, there would be a bigger load, and the voltage was lower... Merging the rails, WOULD solve the issue......right?

Which is the status of modern "new" retro oriented -5V compatible PSUs for AT mainboards? Are there any new ones I'd use on a AT or ATX late 90 system on the market built in modern times specifically for them?