If you are in the US, get a Seasonic 350w for $15.99 shipped.

I pretty much use Seasonic exclusively in all my builds including retro builds.

IF you need the -5v for some reason, you can always buy an adapter that adds the -5v.

https://www.ebay.com/itm/Seasonic-SS-350ET-Ac … ly/401542438766

For an (at least moderately) period-correct PSU choice, some OEM power supply manufactured by Delta would be a good pick. If you find a Dell PSU, make sure it has a P4 CPU power connector because the older (pre-2001) Dell systems used a proprietary pinout, newer Dell PSUs from the Pentium 4 era used standard ATX. A 200W PSU should be enough, but it doesn't hurt to go higher if you can.

If you prefer to go for a newer PSU, look for one made by a good manufacturer. My recommendations for good (newer) PSU brands include Seasonic, EVGA, Corsair, and Cooler Master. Even though Pentium IIIs use the 5v rail for CPU power, they're not as hungry as the AMD Athlon CPUs from that era, so a newer PSU will work fine.

FYI, I started typing this before cyclone3d responded, but this is still relevant.

I'm in Germany, but we have Seasonic as well.

+1 for Seasonic. From my experience Corsair and Cooler Master are hit-and-miss. They like to use crappy caps in low-end models (sweet 350's). I would avoid FSP as well - not nearly as reliable as they were 10 years ago.

Found a Seasonic SS-300FS, now I only need a molex to FDD adapter otherwise I can't power that CF adapter.

^That model certainly has FDD power connectors (two, in fact), unless the one that you found had been modified or something...

Eimer wrote:

I'm about to complete my retro build. Here the specs: […]
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I'm about to complete my retro build.
Here the specs:

• Pentium 3 800E Mhz
  Asus P3B-F Motherboard
  256MB RAM
  Samsung Spinpoint 80GB HDD with 7200 RPM
  3DFX Voodoo 3-3000
  48X (I think?) Teac CD drive
  Gotek USB FDD Emulator
  Soundblaster AWE64
  One CF Card reader on the back

Currently I'm using an AOPEN 250W PSU that came with the case, the case is new and unused but sat in the box in a garage for about 20 years... So it went through a lot of hot and cold transitions...
It does work but I'm paranoid it could blow at some point.

What PSU Brand/wattage would you guys recommend?

I don't really want to spend too much since I'm not even sure if I'm really gonna use the computer that much

I've run a Coppermine 800MHz on an FSP/AOpen PSU of 250W before and it ran fine, though this was years ago and these units have since aged.

I think it's nice to see that this unit still seemed to work well, but the age does make it a bit more yolo when using one of these 🤣

Going period-correct on Power Supplies is generally unwise unless you're going to refurbish them with new capacitors. A modern PSU will be far more reliable, stable, and efficient, and still be completely compatible. You can get MOLEX to Floppy adapters for next to nothing.

The only exceptions are using extremely demanding Motherboard/CPU combos which load the 5V rail, and pre-ATX sized cases.

As far as recommendations, I'd concur with Seasonic. My 10-year-old Corsair, made by Seasonic in this instance, is just starting to give me issues, but it was running a gaming system, and then an always-on Server for the last 7 years. Realistically, any PSU for sale will have enough power capacity to handle a PIII build. I am using a 520W Seasonic Evo in mu Super7 build, but that is because it was on sale, and it had the features that I wanted, particularly Fully Modular cabling.

Tbh I'd recommend exactly the kind of AOpen (i.e. FSP) PSU you already have. No PSU is invulnerable, but these things are pretty near bulletproof. Almost all my retro systems run on period FSP PSUs and I've yet to have any PSU-related issues with them. In case of doubt, open them up and check the caps - but unline Antec they are generally pretty good.

More modern PSUs would also do the trick (assuming you don't need -5V) but I'd only consider them if I couldn't find an FSP box.

I use a current day EVGA 500W Bronze power supply for my P3 933MHz. 500W is overkill for that rig, I'm sure you could go lower and save a few bucks. I've never had any issues. For older mobo's, it's really all about the 5V rail, but as another poster mentioned, you can get an adapter if need be. I'd personally stay away from anything period correct.

Eimer wrote:

Currently I'm using an AOPEN 250W PSU that came with the case, the case is new and unused but sat in the box in a garage for about 20 years... So it went through a lot of hot and cold transitions...
It does work but I'm paranoid it could blow at some point.

If it didn't blow when you turned it on, then I think that concern is greatly reduced by now.
The power supplies that come free with cases are usually very cheaply made, but I don't know if that's true for yours. A crude guideline is to feel how heavy it is. If it's really light then it's junk.

I like to use power supplies that were designed for the period, but they often need recapping. If you don't want to do caps then that option is less appealing.
One that I like is the Fortron FSP300-60PFN, but I might not have that model number quite right. I hasten to add that this power supply definitely needs recapping - every one I've acquired has needed it.

There are also some Enermax models in the 360W-460W range, some of which support heavy loads on both 5V and 12V (they were made in a transitional period). Overkill for this system but useful for their flexibility. I don't have model numbers but I think they're pretty common on eBay and most sellers show the label with the load ratings on it.

KCompRoom2000 wrote:

For an (at least moderately) period-correct PSU choice, some OEM power supply manufactured by Delta would be a good pick.

Agreed. I have a Delta DPS-300PB-2 A power supply and it works very well and reliable. No bad caps.
In Europe, you can get these guys between 15-30 Euros. 😎

Some no-go's I have experienced myself:
- Stay away from period-correct BeQuiet! supplys.
They're crammed with bad caps, often under large heatsinks that you have to desolder to replace them.
They're not worth the hassle, they aren't even that much more quiet compared to a regular power supply.

- The Delta DPS-300 also exists as an OEM variant for Acer. Stay away from that, it's very cheaply made (doesn't even have a power switch).

I am in the plan of building a Pentium 3 system with the following specs:

P3 450 Mhz
Intel 44oBX-2
256 MB RAM
MX440 128MB
Yamaha YMF-719
Creative SB Live!

Since I am planning to use an ISA card, need some advice as to whether a modern PSU would work with ISA cards (read in one forum that ISA cards require -5V which modern PSUs don't provide). In addition, could some one also provide few other power supply options apart from Seasonic as it is not available in my country ? Thanks.

stealthjoe wrote on 2021-09-21, 15:51:

I am in the plan of building a Pentium 3 system with the following specs: […]
Show full quote

I am in the plan of building a Pentium 3 system with the following specs:

P3 450 Mhz
Intel 44oBX-2
256 MB RAM
MX440 128MB
Yamaha YMF-719
Creative SB Live!

Since I am planning to use an ISA card, need some advice as to whether a modern PSU would work with ISA cards (read in one forum that ISA cards require -5V which modern PSUs don't provide). In addition, could some one also provide few other power supply options apart from Seasonic as it is not available in my country ? Thanks.

Hey, hey! I am in the same situation and started a thread asking the same question. I'm hoping some wise souls can help us out in determining what we need. 😀

There are very few cards that require -5v.

ISA Cards & Devices Requiring -5V

As some already mentioned: You've got an Aopen PSU, most likely it's a Fortron that's rebranded. Look at the type name (FSP...)

If it works fine now, it's not likely to blow tomorrow. These are as good as they got in that era. If you insist to get a new one: get another FSP, seasonic, delta... Or any of the rebrands (boring same answer).

If you are ever wondering who the manufacturer is behind a particular brand psu I found this site useful. http://www.realhardtechx.com/index_archivos/P … ewDatabase.html

My preference is most things made by Seasonic or Super Flower.

cyclone3d wrote on 2021-09-21, 18:38:

There are very few cards that require -5v.

ISA Cards & Devices Requiring -5V

Thank you! I also read from another forum to check for the B5 pin on the ISA device. If not there, then no -5V required. I checked the image of the card sent by the seller and it doesn't have the pin. So this confirms it.