You're lucky to get 25A. That would probably be enough for almost any setup, but leaves absolutely no headroom.

I suspect that the voltages may go a little wild when you load a modern high watt PSU with more than 20A on the 5V rail while barely touching the 12V, regardless of printed specs. What you want is recommendations for tried and trusted PSU's.

maybe this a somewhat stupid questions, but why not employ a DC/DC converter to boost 5v power?

That's essentially designing a new output stage. Nothing wrong with it, but it'll be a fair bit of work to do right.

sorry, but i really don't understand that - why would one need to design this anew? just use part of 12v power line to boost 5v output - i can't imagine a dc/dc converter to introduce so much noise/instability as to disallow direct use on a 12 rail...

If the DC DC converter has a similar or lesser output impedance compared to the other supply rail, it will introduce significant ripple. An output filter will be pretty much mandatory. You would also have to properly ballast the two rails together and ensure that the new output network doesn't screw up the voltage feedback loop too badly. There's likely more to worry about, this is just a few things off the top of my head.

Scrounge around for something of the period and when it comes in open the unit up so to inspect for rot cap then refurbish the unit. Brands like Antec, Enermax, and FSP ect made great performing units in the day however they did not age well especially Antec.

nforce4max wrote:

Scrounge around for something of the period and when it comes in open the unit up so to inspect for rot cap then refurbish the unit. Brands like Antec, Enermax, and FSP ect made great performing units in the day however they did not age well especially Antec.

no brand was excluded from the cap rot. Enermax didn't really make high quality ones rather the opposite. Antec and FSP made high quality but the caps were bad anyway.
Currently have a Hiper R and a Antec Truepower, while some people here were rather negative about the Hiper I couldn't help but notice it wasn't less quality compared to the antec.

Such PSU are almost not produced anymore. You may be lucky to find old model which was not in using.
There are still in shops high-end PSU like Corsair AX1200i with 30A, maybe other similar.
Among cheap with reasonable quality: FSP ATX-600PNR with 24A.
Also there are cheap "nonames", but I doubt you'd want to risk using them on retro stuff.

Tertz wrote:

Such PSU are almost not produced anymore. You may be lucky to find old model which was not in using. There are still in shops hi […]
Show full quote

Such PSU are almost not produced anymore. You may be lucky to find old model which was not in using.
There are still in shops high-end PSU like Corsair AX1200i with 30A, maybe other similar.
Among cheap with reasonable quality: FSP ATX-600PNR with 24A.
Also there are cheap "nonames", but I doubt you'd want to risk using them on retro stuff.

My old corsair 750 had 3xA on the 5V which was from 2011, so 1200 is abit overkill and expensive too.

Keep a lookout for Zalman power supplies. They seemed to make some really nice PSUs back in the day. About a year ago I pulled a 400w Zalman out of a dumpster Athlon XP machine. The motherboard had bad caps, but the PSU (manufactured 2003) was absolutely perfect. It weighs a ton, has a very quiet fan, and an impressive 40A 5v rail. I use it to power my PIII, a Tualatin-1575 with 2GB of DDR and a GeForce 6800GT.

It's no dual Athlon MP, but hey, at least it's overclocked!

I am running a Kentek 680Watt PSU in my Pentium 3 box. It's probably a craptastic model, but it has served me well for about 6 months now. It's rated for...drumroll...50 amps on the +5 volt rail. Not sure how much truth is in that.

Thanks for all the replies there is some very useful information there. So it looks like my options are:

New very high wattage quality PSU.

New low cost / no name PSU.

New old stock older style PSU.

Used old style PSU.

Or I guess go down the server rough of dual PSU.

None are ideal unfortunately. I think I will have to go count my pennies and have a think.

cj_reha wrote:

I am running a Kentek 680Watt PSU in my Pentium 3 box. It's probably a craptastic model, but it has served me well for about 6 months now. It's rated for...drumroll...50 amps on the +5 volt rail. Not sure how much truth is in that.

its posible, most likely they put down the maximum possible A used on the combined 5V en 3,3V rail which in this case should be atleast 250A, rather high but a dream come true for any Athlon XP build which usually requires around 30A on the 5V rail.

Richo wrote:

its posible, most likely they put down the maximum possible A used on the combined 5V en 3,3V rail which in this case should be atleast 250A, rather high but a dream come true for any Athlon XP build which usually requires around 30A on the 5V rail.

I feel the most optimistic result is that the PSU is generally okay but the paper rating grossly inflated. It's entirely possible this example is much, much worse, though.

I just checked the PSU that I use as the PSU of choice for my retro builds and it has a 38A +5V rail. It's truly the best PSU you can ask for with ATX retro builds. It has good -5 and -12v lines, a 20+4 ATX connector, not to mention a healthy combination of SATA, Molex, and FDD power. One of them has been in use for probably 4-5 years now and has not skipped a beat.

It is of course most any Logisys PSU that can be bought off of Newegg
https://www.newegg.com/Product/ProductList.as … 1624&IsNodeId=1

I have the 480w one in my Pentium 3, and a 550w one that was in my PC gaming rig up until a bit after I got my GTX 970, They can handle anything that doesn't need PCI-E 6 pin power pretty much.

I wouldn't trust your Logisys PSU based on their track record.
https://www.google.ca/search?q=logisys+teardo … d7jI-fKjwTLu74w
http://www.johnnylucky.org/power-supplies/psu … lemon-list.html
http://www.overclockers.com/logisys-ps480x2-review/

gdjacobs wrote:

I wouldn't trust your Logisys PSU based on their track record. https://www.google.ca/search?q=logisys+teardo … d7jI-fKjwTLu74w h […]
Show full quote

I wouldn't trust your Logisys PSU based on their track record.
https://www.google.ca/search?q=logisys+teardo … d7jI-fKjwTLu74w
http://www.johnnylucky.org/power-supplies/psu … lemon-list.html
http://www.overclockers.com/logisys-ps480x2-review/

I enjoyed reading overclockers post, gave me a chuckle.
Imo they should start make a higher standard for psu in the future to prevent garbage/hazardous psu to enter the market. They are a possible fire hazard after all.
I learned my lesson with a sweex PSU which exploded on me.

Yeah the overclockes link is funny.

I like the warning on the psu.
http://www.overclockers.com/wp-content/upload … fuseWarning.jpg

https://www.newegg.com/Product/Product.aspx?I … =9SIAD245CD9824
http://www.frostytech.com/articleview.cfm?art … eid=1655&page=1
Bit cheaper on amazon. Not used it myself. Not sure how they still have these in stock, the earliest reviews I can find are from 2002. Internals have probably changed since then, etc.