I've got a PIII 600 Katmai (the highest wattage PIII in stock form) on a P3B-F with a TNT2 Ultra, a bunch of PCI cards, single HDD and standard DVD + 3.5 floppy. It runs just peachy on a 400W Aopen power supply that was included in an H500A case. It's got a pretty weak 5V output too, I think 16A at most. I do have to disable the -5V and PSU fan speed warnings in the BIOS.

Some of the Corsair power supplies on Newegg have a 25A 5V rating. That should be plenty for a PIII setup. Modern power supplies don't like 5V-heavy loads without much on the 12V, but I haven't had issues with this dinky Aopen unit.

I also have a Katmai 600MHz Pentium III Slot 1 in an ASUS P2B Revision 1.02, 256MB of PC-100 SDRAM, Diamond Viper V770 (TNT2) 32MB AGP, 2x 12MB Voodoo2 PCI cards, 10/100 PCI ethernet, AWE64 ISA sound card, hard drive, CD-RW, ZIP-100... all pushing from an AGI HEC-300A PSU with 30A on the +5V rail and 15A on the +12V rail. I haven't had any problems that could be traced to the PSU.

I've also used a Cooler Master RS-500-PCAR-D3 500-Watt PSU that has 25A +5V and 18A +12VA/B and it also worked fine.

I use Antec Basiq's - I have 3 in action and they seem OK

http://store.antec.com/basiqseries/bp350.html

My P-III Katmai 600 box (yes, I have one too) is running off a Supermicro PWS-305-PQ, which is a 300w 80Plus Bronze unit built by Delta. The 5V rail is just 13A... without stability issues. (I'm sure an Athlon XP build with this PSU would be impossible.)

According my notes when I was still setting it up, the machine pulls 34.5w from the wall at idle and 53.6w during Cinebench R10's CPU test. That was in WinXP... it might consume slightly less within Win98SE.

I power dual P3-S 1400 MHz, 2 GB of RDRAM, a GF4 Ti4600, V2 SLI, and other goodies with a Seasonic M12II 520 Evo: 520W, 24A on the 5V, 3.3V and 5V combine to 130 W, 80Plus Bronze, and fully modular. So far, so good!

My Pentium 3-S 1.4GHz Tualatin daily driver uses a Corsair CX500M. Despite the mixed reviews (it's a first gen CX500M) it seems a good, solid unit. It works very well and has enough headroom for my graphics card, in terms of amperage on the +12V rail.

Just find old Delta PSU from some workstation they are very solid, or some EnermaX like Coolergiant series or other, they will fit great...
No point of paying too much for new PSU, when they are old solid cheap solutions, also they have way greater +5V rails, and that is what matters for old builds..

Agreed. Seasonic (frequently rebranded as AOpen) and Enlight are also good brands, with better caps than Antec (not that that's too hard...).

I recently picked up a Seasonic 350W with 30A on the 5V line, both -12V and -5V present, ATX20p, but also ATX12V 'P4' and 6-pin AUX connectors. Oh and a few SATA as well. Pretty much the ultimate 'old style' ATX PSU in other words. Best measure of quality as usual: sheer weight. This thing weighs a ton (and no, that's components and heatsinks, not a block of concrete faking it). It cost me all of EUR 5.

No way would I mess around with a more expensive modern PSU instead - to get 30A on 5V would with similar build quality would cost me 15 times as much, I still wouldn't get -5V and -12V, or that AUX connector, and most of the PSU (the massive 12V line(s)) would be completely wasted.

I tend to forget things...
AOpen i whatever it is was involved before it is quality part, no matter what it is..
I have AOpen AT PSU, and the quality is outstanding even for 386 build is way too overkill, it is heavy, and the x2 big caps inside are Nippon..........
Also the old Fortron (not FSP group) units are very well made, the FSP is ok too, but all the caps inside are junk, and they tend to fail way faster, one replaced all caps it will be good. Also i think Antek old PSU are good, not sure who was the OEM, Delta or Seasonic.

That is the idea, ols PSU are cheap, better build, and they have proper voltage on the rails that matters, while is absolutely not good to buy new PSU that cost like 50-70$ and it have lower quality and weak +3.3v and specially +5v rails...

Radical Vision wrote:

Just find old Delta PSU from some workstation they are very solid, or some EnermaX like Coolergiant series or other, they will fit great...
No point of paying too much for new PSU, when they are old solid cheap solutions, also they have way greater +5V rails, and that is what matters for old builds..

dionb wrote:

...No way would I mess around with a more expensive modern PSU instead - to get 30A on 5V would with similar build quality would cost me 15 times as much, I still wouldn't get -5V and -12V, or that AUX connector, and most of the PSU (the massive 12V line(s)) would be completely wasted.

So... What modern PSU powers your Pentium3 setups? 😎

I did use a Antec VP350P.... which subsequently may of killed my D815EEA2 mainboard.

slivercr wrote:

Radical Vision wrote:

Just find old Delta PSU from some workstation they are very solid, or some EnermaX like Coolergiant series or other, they will fit great...
No point of paying too much for new PSU, when they are old solid cheap solutions, also they have way greater +5V rails, and that is what matters for old builds..

dionb wrote:

...No way would I mess around with a more expensive modern PSU instead - to get 30A on 5V would with similar build quality would cost me 15 times as much, I still wouldn't get -5V and -12V, or that AUX connector, and most of the PSU (the massive 12V line(s)) would be completely wasted.

So... What modern PSU powers your Pentium3 setups? 😎

For now my PIII machine is suspended, as i don`t have mobo for PIII, but soon the P3B-F will be here, as my ABIT BE6 need some repair, bcuz it seems the transistors are dead or something..
I using in my both of mine Slot 1 machines Delta power units, one EOM Compaq, and one OEM HP, they have great quality specially the HP one, as it have all japan caps inside...

Also, if you want a "new" PSU that has some flexibility for older setups like Pentium 3 and Athlon/XP that also has -5V for ISA cards, the Startech ATXPOWER300 seems like a really solid option. I've been considering picking one up as my testbench PSU. It's got a 30A 5V rail with a 180W max for 3.3+5V, but also a decent 180W on the 12V rail, 279W combined across both. I can't speak to the quality since I haven't bought one yet, but it's a compelling choice if you want something brand new that's also reasonably priced.

I will not even consider PSU like this one, as it will blow up some day, and it have chance to blow up the whole computer with it, i have seen that things, with junk brand power units...

Radical Vision wrote:

I will not even consider PSU like this one, as it will blow up some day, and it have chance to blow up the whole computer with it, i have seen that things, with junk brand power units...

Is there something specific about this brand or model that indicates it's of poor quality? Options for new power supplies with 30A on 5V are very limited, and this one has solid reviews on Amazon and Newegg.

Katmai500 wrote:

Radical Vision wrote:

I will not even consider PSU like this one, as it will blow up some day, and it have chance to blow up the whole computer with it, i have seen that things, with junk brand power units...

Is there something specific about this brand or model that indicates it's of poor quality? Options for new power supplies with 30A on 5V are very limited, and this one has solid reviews on Amazon and Newegg.

It was not made by Compaq nor ever used in a retail Compaq system?

Really.... The price, the name NOname, also look the caps onside, the quality of the wires, the better power units have better cables that are fatter, better connectors, while the junk PSUs have thinner cables like small rope, the connectors are cheap and they fit most of the time hard on some places. Also the fan will be some chinese, instead of Delta, Minebea, AVC, Sanyo Denki. No proper proper protection if the PSU fails, or over current protection.... Also i bet this PSu is from the light ones, and is not real 30A on +5V, for cheap power units will be more like 15-20 amps on the +5v. Or if by some lick it have 30 amsp on 5V (i reaaaaly doubt it) when you put something like Athlon XP 3200+ and Radeon x1950 Pro AGP (not to mention HD 3850 AGP) this unit will fail, maybe not from the start but short time after.....

For f**k sake just find some Delta PSU from HP or Compaq and compare it to your new junk PSU, and you will see for what im talking, or if you want i have here test Delta 300W PSU i will make pictures of it to show you for what im talking about. Also i have here junk PSUs from some computers some people did giveaway to me, and i found them inside, like JNC, KME and such trash, so is not hard for me to make comparison between junk unknown chinese PSU and some Delta, EnermaX or Aopen as they are good build as well.............

Skyscraper wrote:

It was not made by Compaq nor ever used in a retail Compaq system?

Compaq is not the manufacturer of any of the things they have, they are just designer like HP is, DELL is, Compaq uses OEMs to manufacture all the parts for them, but all is branded as the Compaq name.
That is not the case with IBM, that did have their own things like HDDs, Keyboards, processors and others...

Radical Vision wrote:

Really.... The price, the name NOname, also look the caps onside, the quality of the wires, the better power units have better c […]
Show full quote

Really.... The price, the name NOname, also look the caps onside, the quality of the wires, the better power units have better cables that are fatter, better connectors, while the junk PSUs have thinner cables like small rope, the connectors are cheap and they fit most of the time hard on some places. Also the fan will be some chinese, instead of Delta, Minebea, AVC, Sanyo Denki. No proper proper protection if the PSU fails, or over current protection.... Also i bet this PSu is from the light ones, and is not real 30A on +5V, for cheap power units will be more like 15-20 amps on the +5v. Or if by some lick it have 30 amsp on 5V (i reaaaaly doubt it) when you put something like Athlon XP 3200+ and Radeon x1950 Pro AGP (not to mention HD 3850 AGP) this unit will fail, maybe not from the start but short time after.....

For f**k sake just find some Delta PSU from HP or Compaq and compare it to your new junk PSU, and you will see for what im talking, or if you want i have here test Delta 300W PSU i will make pictures of it to show you for what im talking about. Also i have here junk PSUs from some computers some people did giveaway to me, and i found them inside, like JNC, KME and such trash.........

Skyscraper wrote:

It was not made by Compaq nor ever used in a retail Compaq system?

Compaq is not the manufacturer of any of the things they have, they are just designer like HP is, DELL is, Compaq uses OEMs to manufacture all the parts for them, but all is branded as the Compaq name.
That is not the case with IBM, that did have their own things like HDDs, Keyboards, processors and others...

Yea I kind of know 😉

While I agree that Delta makes good PSUs even a new 300W "crap PSU" will last a decade or two powering a Pentium III system needing about 100w peak. I doubt it will get much warmer than ambient even if its efficiancy only is ~70%.

I'm not saying that the worst $10 Chinese Ebay junk PSU will hold up but I doubt the Startech unit is that bad.

Capacitor choice might not be the greatest (although I'm not really sure). I suspect, based on teardowns of other Startech supplies, that the design is safe and complete. The only sure way to know is a transient and ripple test followed by an internal inspection. A full range load test is also excellent, although not everyone has their own ATX load tester sitting around.

Delta is a top notch manufacturer along with Lite On, Zippy, Etasis, etc. Lots of other PSUs aren't quite at the build quality of those. That doesn't mean they're crap.