Phil made a good video on this subject: https://www.youtube.com/watch?v=efK7mw8eYiE

I use a Seasonic SS-650KM for my Socket A build, it has 25 amps on the +5 rail and it has worked well for me. I was lucky to get it for a pretty low price, but there are newer ones that are very similar.

My Thermaltake Xaser III 480 is rated for 40 amps on the +5, but it began to falter when I was overclocking my Sempron 3300+ (rebranded XP3200) with the +5 falling below 4.8 volts according to the readings from Motherboard Monitor. I swapped in the Seasonic, and so far it hasn't faltered. This is with an optical drive, an SSD, a couple of 140 MM fans and a GeForce 6800 Ultra.

20 amps on a Corsair I have seems to top out around 2.2ghz for me, perhaps a little higher. It's not worth overclocking a Socket A in my opinion, just build a stronger system. Socket A strength lies in adaptability and being able to clock down to 300mhz.

A psu with 25amps minimum on the 5v rail should work. An XP 3200+ can draw near 20Amps off the 5v. Rounded: An HD needs 1A, a CDROM/Burner 1A, both off the 5v and 12v...
The DDR and AGP video card is mostly powered off the 3.3v AND/OR the 12v depending on board design (and which they want to VRM from, is rare is the 5v line to avoid noise).. iirc speaking of Soc A.

there are socket A boards using 12V for cpu power, for example https://theretroweb.com/motherboards/s/msi-kt … bo-l-ms-6764-v1

rasz_pl wrote on 2023-09-12, 07:11:

there are socket A boards using 12V for cpu power, for example https://theretroweb.com/motherboards/s/msi-kt … bo-l-ms-6764-v1

What I’ve gathered, it still varies how much those boards actually draw from 12V line for CPU. Many of them are still very heavy on 5V.

In the end, I personally decided to recap the secondary of two old Enermax PSUs. The other is mainly for bench purposes, at least for now, but both deliver 32A to 5V line. As far as recapping goes, it is quite smooth job as PCBs, although a bit crowded, are very simple in these. It took longer time to map the caps and make an order for quality replacements than it was to actually desolder old caps and resolder new ones.

Both PSUs were made with mostly CEC PCE-TUR caps and the beefier of these had few low ESR TUL series also. I measured quite few of them and they seemed to be still in spec, but hardly something that should be relied anymore after 20 years or so.

Look for something with 30A (preferrably 35A) or above on the 5V rail

I think it's safe to say that you won't use +5V CPU rail motherboard with an Athlon XP rated at 3200+. Any modern PSU will work with your typical Nforce 2 motherboard with +12V CPU rail just fine. Well, obviously not with ASUS nForce 2 trash, which should be avoided.

For +5V systems, I use a FSP power supply rated to work at 30A +5V and combined +3.3/+5 output of 180 watts. That's enough to get the Athlon XP 3000+ to be oveclocked on KT333. Although I can't recommend using such system for prolonged period of time, because ATX connector is operating at dangerously high temperature.

I bought an mobile Athlon 2600+ to see if/how well it will work in my Soyo Dragon Plus, but I thought I'd try it out in my 8KRA2+ first. I got it a little higher than the Sempron 3000+ (yay) but I hit the limit of the heatsink and can't go any further unless I get something better (boo). The Seasonic PSU is holding the line like a champ!

CharlieFoxtrot wrote on 2023-09-12, 08:03:

rasz_pl wrote on 2023-09-12, 07:11:

there are socket A boards using 12V for cpu power, for example https://theretroweb.com/motherboards/s/msi-kt … bo-l-ms-6764-v1

What I’ve gathered, it still varies how much those boards actually draw from 12V line for CPU. Many of them are still very heavy on 5V.

Board either uses 5V or 12V for CPU Vcore. If it uses 12V rail then 5V draw is miniscule, couple of watts for chipset/ram/expansion cards/io chips.
You can look at ms-6764 diagram yourself https://drive.google.com/file/d/1yXKkMTRVKarW … ew?usp=drivesdk page 36

rasz_pl wrote on 2023-09-12, 20:46:

What I’ve gathered, it still varies how much those boards actually draw from 12V line for CPU. Many of them are still very heavy on 5V.

Board either uses 5V or 12V for CPU Vcore. If it uses 12V rail then 5V draw is miniscule, couple of watts for chipset/ram/expansion cards/io chips.
You can look at ms-6764 diagram yourself https://drive.google.com/file/d/1yXKkMTRVKarW … ew?usp=drivesdk page 36
[/quote]

Nice ! My QDI Kudoz 7X/600 they are def off the 5v, will have to check the MSI K7T266 Pro 2...know the ECS K7S5A is off 5v.
If off the 12v Wonder how they are getting all those amps from one wire on the 20pin ATX (there are 4 for 5v)....

Horun wrote on 2023-09-13, 02:36:

will have to check the MSI K7T266 Pro 2
If off the 12v Wonder how they are getting all those amps from one wire on the 20pin ATX (there are 4 for 5v)....

there appear to be many submodels, for example K7T266 Pro2-U https://www.manualslib.com/manual/820139/Msi- … 593.html#manual has additional 12V socket, I think back in te day it was called "P4" plug? because it was popular on P4 boards = 12V CPU supply

Athlon XP 3200 requires a motherboard with nforce2/KT600/KT880 chipset and with the notable exception of Asus almost all have the auxiliary power connector. That being said you will still need a PSU with a beefy 5V rail. Period correct Enermax are built like a tank and would require capacitors to be changed only in rare cases; Modern Corsair is what I use and are exceptional well built; I have a RM1000i with 25A on the 5V rail and 150w combined on the 3.3&5V - still available for sale and not the same PSU as the newer revisions!! - that I use for testing most new stuff and handles just fine even a 20 pin only build made up of Athlon XP 2400/Abit KG7 raid/2gb RAM/geforce 2/HDD/DVD.
As a side note: be prepared to spend quite a bit if you want the best of the best!

The video card is an important variable.
A Radeon 9800 draws heavily from the 5V rail. I think the following generation X800/etc cards draw mainly from the 12V rail.

nd22 wrote on 2023-09-13, 06:30:

Athlon XP 3200 requires a motherboard with nforce2/KT600/KT880 chipset and with the notable exception of Asus almost all have the auxiliary power connector. That being said you will still need a PSU with a beefy 5V rail. Period correct Enermax are built like a tank and would require capacitors to be changed only in rare cases; Modern Corsair is what I use and are exceptional well built; I have a RM1000i with 25A on the 5V rail and 150w combined on the 3.3&5V - still available for sale and not the same PSU as the newer revisions!! - that I use for testing most new stuff and handles just fine even a 20 pin only build made up of Athlon XP 2400/Abit KG7 raid/2gb RAM/geforce 2/HDD/DVD.
As a side note: be prepared to spend quite a bit if you want the best of the best!

Sadly for me, my 8KRA2+ (KT600) does not have the P4 socket, so PSU choice is especially critical.

shamino wrote on 2023-09-13, 12:54:

A Radeon 9800 draws heavily from the 5V rail.

afaik every 9800 has molex and draws power from yellow cable = 12V

rasz_pl wrote on 2023-09-13, 20:07:

shamino wrote on 2023-09-13, 12:54:

A Radeon 9800 draws heavily from the 5V rail.

afaik every 9800 has molex and draws power from yellow cable = 12V

Apparently it's very different between the 9800Pro and 9800XT
https://web.archive.org/web/20160331082016/ht … owercons_7.html

The 9800Pro still heavily uses the 3.3V and 5V rails, but the 9800XT shifts load to 12V to balance it out.
These are that article's overclocked "burn" measurements, so it should be worst case scenario (which you'd want to plan for in a PSU selection):
9800Pro:

13.3V  5.08A  15.74W
25V    6.08A  29.75W
312V   0.62A   7.33W

9800XT:

13.3V  3.84A  12.12W
25V    4.8 A  24.0 W
312V   2.71A  31.6 W

So it seems the design of the 9800XT isn't just a higher clocked 9800 Pro. Apparently the power budget required them to rearrange where the power was coming from on that card.
The X800 Pro/XT also balances it more like the 9800XT does.
So it looks like 9800XT is the point when ATI started making real use of the +12V rail, and that continued into the X800/etc.
==========

Although it doesn't count as a "modern PSU", I had a good experience with a high end Athlon XP system using an FSP300-60PFN. That PSU was more +5V oriented, but the nForce2 motherboard used +12V for the CPU. The overall load for the complete system balanced well with that PSU. All the voltage rails had healthy readings and I used it for about 2 years without a problem.
That PSU did have bad caps though. Not a big deal if you can replace them but the thread title implies a desire to avoid recapping.

That same system fell over with a more modern 550W PSU which didn't have enough juice on the +3.3V rail. It's a quality PSU and I've used several on more modern, power hungry machines. The only one that died on me was the one I tried in the Athlon XP.

Repo Man11 wrote on 2023-09-11, 21:45:

Phil made a good video on this subject: https://www.youtube.com/watch?v=efK7mw8eYiE

It's very intriguing to see that Corsair VS450 with only 100W output from +3.3V and +5V combined can power up Duron 1GHz + GF3Ti500 with ease, while FSP HE-500 with (claimed) 120W output from +3.3V and +5V combined cannot.

Repo Man11 wrote on 2023-09-11, 21:45:

I use a Seasonic SS-650KM for my Socket A build, it has 25 amps on the +5 rail and it has worked well for me. I was lucky to get it for a pretty low price, but there are newer ones that are very similar.

My Thermaltake Xaser III 480 is rated for 40 amps on the +5, but it began to falter when I was overclocking my Sempron 3300+ (rebranded XP3200) with the +5 falling below 4.8 volts according to the readings from Motherboard Monitor. I swapped in the Seasonic, and so far it hasn't faltered. This is with an optical drive, an SSD, a couple of 140 MM fans and a GeForce 6800 Ultra.

The PSU came with my Asus A7V133-C + V7100PRO/64M (GeForce2 MX 400) was a nameless 250W, with 10A on +3.3V and 20A on +5V (there's no spec on combined output!) yet the system can POST with GeForce FX 5600 XT installed.

shamino wrote on 2023-09-13, 22:18:

The 9800Pro still heavily uses the 3.3V and 5V rails, but the 9800XT shifts load to 12V to balance it out.

Medion Radeon 9800XL works purely from an AGP slot (despite having a floppy connector) and I doubt MSI (OEM manufacturer for Medion) deviated that far from the reference design. So yeah, +3.3v and +5v are the main source of power for R300/R350 cards.

nd22 wrote on 2023-09-13, 06:30:

A Period correct Enermax are built like a tank and would require capacitors to be changed only in rare cases

I went to the vintage PSU route so that I don't need to think that much about the MB VRM or GPU and I can slap any board in the system if I want. I got Enermax EG365AX-VE(g) and slightly newer Noisetaker EG495AX-VE (W) ATX2.0 PSU, both deliver 32A to 5V and 3.3V rails. Both PSUs were full of CEC manufactured PCE-TUR general usage caps and the newer had few TUL series low ESR caps.

Yes, none of the caps were bloated or leaked and I measured quite a few them and they were still in spec. However, CEC caps are clearly 2nd tier and what I read about them, they are a bit like TEAPO, which means that there is a variance in quality how well they last: sometimes they work just fine for an eternity, sometimes they die early. If you have caps from a bad batch, you may have a problem in the long run. Of course usage profile of the PSU plays a role in what condition caps are. Unfortunately when buying a second hand, you don't know anything about the PSU history: how many hours, how high temperatures, how it was stored in recent years etc.

After 20 years I wouldn't trust these capacitors anymore, especiall not knowing about the history. And that is why I recapped secondary sides on both, even though in my case caps seemed to be still good both visually and after measuring quite many of them. There is clearly a risk when using these old PSUs in original condition. But if you do electronics work in any case, recapping these shouldn't be a huge effort and in that case I wouldn't skip recapping them, even though these PSUs are considered relatively reliable.