I am spitballing it at around 160 watts at the moment, and figure it would be fine for graphics up to 1st gen DX8 .. gF3/8500 stock clocks, but needs 300+ for 9500+

If my memories are right the Radeon 9800 has 47W TDP. If the PSU is of decent quality and properly serviced, I wouldn't worry.

All PSU give about 75- 85% of their rated wattage.
Even those with bronze, silver, gold ratings they are efficiency but not a guarantee of 100% peak.
This is due to the fact the rating printed on the things is the PEAK or absolute maximum it can provide.
There are other things to consider such as mains supply voltage that it also is a peak rating never an even 120v 220v 240v a multimeter can show this.
Generally the more watts the PSU can supply the longer the "crap" lives.
I just removed a PSU from a 2006 PC tower because although it supplies a peak of 550 watts it got hot.
Many little fan ones do but the new age large quiet fan ones don't sound like a wind tunnel anyhow.
I say the "crap" doesn't like heat so checking for a hair dryer breeze blowing out the back like i did prevents disaster.

zapbuzz wrote on 2021-11-07, 21:23:

There are other things to consider such as mains supply voltage that it also is a peak rating never an even 120v 220v 240v a multimeter can show this.

Nope, it's RMS voltage. The peak is sqrt(2) times higher.
Same with PSUs. If it's not some low rated garbage, it can handle the load it's rated for. Not ideal and I wouldn't recommend running a PSU like that, but it's not some transient peak like the P.M.P.O. rating for speaker systems.

Which AOpen 250W PSU is it exactly?

If it's a 5V-heavy ATX 1.x P3/Athlon design, 250W is more than sufficient. It's likely to be manufactured by FSP, which (if the caps are still good...) is excellent.
If it's a newer 12V-heavy ATX 2.x P4 design, it might not be able to deliver enough on the 5V line for this stuff. Also, 250W in that segment is bottom-scraping low-end and might not be an FSP design.

dionb wrote on 2021-11-07, 22:15:

Which AOpen 250W PSU is it exactly?

If it's a 5V-heavy ATX 1.x P3/Athlon design, 250W is more than sufficient. It's likely to be manufactured by FSP, which (if the caps are still good...) is excellent.
If it's a newer 12V-heavy ATX 2.x P4 design, it might not be able to deliver enough on the 5V line for this stuff. Also, 250W in that segment is bottom-scraping low-end and might not be an FSP design.

Im not too sure exactly at the moment but i think its a variant of the fsp250-60gt models. Its the stock one that came with the ht45 case and mine was manufactured late 2000 used regularly since.

My personal advice is to use a multimeter, and stick the measurement needles into a Molex HDD connector measuring the voltages when the computer is doing some work (maybe running some Quake timedemo, Prime95 etc) and see yourself.
This is a very simple basic test every technical layman can do without big investments of time/money or risk.

You will want to make sure that +5V does not drop below 4.75V and 12V does not rise higher than 13.2V.
Personally I dislike FSP PSUs because these have only a narrow loading ratio where these limits are kept.
FSP is in good regard by many people here, which I suspect is not caused by rational reasons (eg actual measurements and specification compliance tests)
So it is always best to take your measurements yourself and judge from what you find.

Y2KBazo wrote on 2021-11-07, 23:12:

dionb wrote on 2021-11-07, 22:15:

Which AOpen 250W PSU is it exactly?

If it's a 5V-heavy ATX 1.x P3/Athlon design, 250W is more than sufficient. It's likely to be manufactured by FSP, which (if the caps are still good...) is excellent.
If it's a newer 12V-heavy ATX 2.x P4 design, it might not be able to deliver enough on the 5V line for this stuff. Also, 250W in that segment is bottom-scraping low-end and might not be an FSP design.

Im not too sure exactly at the moment but i think its a variant of the fsp250-60gt models. Its the stock one that came with the ht45 case and mine was manufactured late 2000 used regularly since.

25A on the 5V line, if it can actually (still) supply that voltage under load it should be fine.

retardware wrote on 2021-11-07, 23:42:

My personal advice is to use a multimeter, and stick the measurement needles into a Molex HDD connector measuring the voltages w […]
Show full quote

My personal advice is to use a multimeter, and stick the measurement needles into a Molex HDD connector measuring the voltages when the computer is doing some work (maybe running some Quake timedemo, Prime95 etc) and see yourself.
This is a very simple basic test every technical layman can do without big investments of time/money or risk.

You will want to make sure that +5V does not drop below 4.75V and 12V does not rise higher than 13.2V.
Personally I dislike FSP PSUs because these have only a narrow loading ratio where these limits are kept.
FSP is in good regard by many people here, which I suspect is not caused by rational reasons (eg actual measurements and specification compliance tests)
So it is always best to take your measurements yourself and judge from what you find.

Nothing more rational than over two decades of trouble-free use in a lot of systems including some pretty demanding ones (overclocked AthlonXP on boards without ATX12V). Had a few recently that had failed due to bad caps - but after 20 years that's hardly surprising. FSP may not be the best out there, but it's solid (heavy) stuff, unlike things like Q-tek and Sweex. I'm sure an Antec with good caps would perform better on paper, but good enough is good enough. If it is - which is an issue after 20 years regardless of brand.

That said, fully agree that measuring under load is the best indicator.

MHO: The PSU should be OK for what you are going to use it for. If for an Athlon would suggest at least a 300 watt or better with 30+ amp +5v...
from late 1990's to mid 2000's Sparkle Power, PC Power and Cooling, Antec, Seasonic were all good (and still are if the caps lasted). A 25amp +5v back then actually meant it from the good names.
@ retardware: where do you get +12v at +13.2v ? no good PSU +12v should ever exceed about +12.6 even according to that wiki ;p What is important is that it does not drop below 11.5v or rise above 12.5v under load.
Agree use a Volt meter and check it's volts both idle and doing something under load 😀

Horun wrote on 2021-11-08, 01:24:

@ retardware: where do you get +12v at +13.2v ? no good PSU +12v should ever exceed about +12.6 even according to that wiki ;p What is important is that it does not drop below 11.5v or rise above 12.5v under load.

oops I confused something. 🤦
The tolerances are usually +- 5% but in some versions of the ATX specification there are bigger tolerances for +12V.

Whatever, the main problem with many PSUs is that when they get strong load on +5V, then either
- the +12V goes up... have had some PSUs on the test bench that managed to reach 14.8V. A real joy for HDD motor controllers!
...or...
- if there is a limiter on +12V preventing it going too high, then on some PSUs the +5V drops. The winner in this PSU class I had on my test bench managed to drop down to 4.0, 4.1V. At such voltages system stability issues are highly likely (if the system starts up at all), and it puts a lot of strain on the CPU/AGP switching regulators, too.

Y2KBazo wrote on 2021-11-07, 18:58:

Was thinking about swapping out my TNT2 Ultra in my millennium machine for a gf2 GTS or a 9700/9800 but im a bit worried about o […]
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Was thinking about swapping out my TNT2 Ultra in my millennium machine for a gf2 GTS or a 9700/9800 but im a bit worried about overstepping my 20 year old 250 watt aopen psu that is running everything under the sun already.

In the machine ive got a pIII 733 on an AX34 board with 256 in all 3 slots.
Diamond Viper V770 TNT2 Ultra
A soundblaster live 4760 with live drive and a yamaha YMF724 card of sorts
Some dlink 10/100 lan card
Promise Ultra133 laying dormant.
160gb wd blue hard disk
Dvd and cd writer, 3.5 flopp and 750mb ZIP
2 modern 90mm fans
Wondering if id blow up my machine with all these accesories and a more modern t&l card, and if there was a place to look up power consumption figures on older hardware like this?
Thanks a bunch!
20211028_150326_HDR.jpg

If your PSU is still in good working order, I think it should be enough to power your rig.
235W was enough for a Deschutes and 300W FSP PSUs was enough to power basically any Athlon XP CPU provided they had the 5v power (something like 30A).

I suppose you mean 92mm fans? Or 80cm but either way it doesn't really matter for the topic anyway but best to clarify if you want a clarified answer 😜

For CPUs there's still this site
https://www.pchardwarelinks.com/elec.htm
Your CPU should be roughly 20W for example, so relatively cool. Your graphics card should also not be a powerhog despite it having a (tiny) fan.

Having said that, you might be better off with a brand new PSU unless you know what you are doing. These units are basically ancient by now.

Thanks a bunch for all the tips and info everyone! Im going to test the old psu with a millimeter under load and make sure the voltages are proper like recommended for the time being but for the long run with how many hours have been put on this machine i think im going to grab a modern psu with a good 5v rail. Probably be good since i plan on putting a couple more disks in the machine 🤣