There was a guy selling adapters with -5v and dummyload a while back, but it seems they left eBay 🙁

Maybe someone knows where their at?

Eitherway a passive adapter should work fine. The -5v rail is only used by a handful of old Isa cards. Mostly sound.

For Sound blaster anything SBPro 2 and up will be fine without it and for the adapter power switch, you can get a one off an old AT PSU or online.

Iv used EVGA 500watt PSUs in my builds. Good quality and a decent price. Any name-brand 400-500watt should more then suffice 😀

SodaSuccubus wrote on 2020-06-03, 19:26:

Eitherway a passive adapter should work fine. The -5v rail is only used by a handful of old Isa cards. Mostly sound.

Here is a thread that lists the various cards that require a -5v rail.

ISA Cards & Devices Requiring -5V

@SodaSuccubus - Thank you for the advice, I wasn't sure if a newer PSU was safe due to the higher amps the PSUs provide.

@Ozzuneoj - Thank you very much for the information, looks like I do not need a -5V at all with the ISA sound card I intend to use.

SodaSuccubus wrote on 2020-06-03, 19:26:

There was a guy selling adapters with -5v and dummyload a while back, but it seems they left eBay :( […]
Show full quote

There was a guy selling adapters with -5v and dummyload a while back, but it seems they left eBay 🙁

Maybe someone knows where their at?

Eitherway a passive adapter should work fine. The -5v rail is only used by a handful of old Isa cards. Mostly sound.

For Sound blaster anything SBPro 2 and up will be fine without it and for the adapter power switch, you can get a one off an old AT PSU or online.

Iv used EVGA 500watt PSUs in my builds. Good quality and a decent price. Any name-brand 400-500watt should more then suffice 😀

To give you an idea, my Asus P3B-F with 750MHz P3 (underclocked 1GHz) with Geforce 6200 draws less than 100W from the wall at idle using a PSU rated at about 70% efficiency (so less than 70W actual power use). With a Pentium 1 (which draws less than a Pentium 3), I would guess you would probably be fine with something that provides in the range of 110W or more combined on 3.3V and 5V rails (unless you go overboard with extra cards and drives).

gryffinwings wrote on 2020-06-03, 18:19:

I'm not seeing the ones that have the dummy load and give -5v. Does anyone know where to find the ones with the dummy load and -5v?

Some modern PSUs use DC-DC conversion to generate the 3.3V and 5V lines from the 12V internally. These PSUs do not need a dummy load on the 12V, since the conversion for the lower voltages is already putting a load on the 12V. Check power supply spec sheets and reviews for this feature - I personally use a Corsair CX series power supply in my Socket 7 (K6-III+) build.

As long as they can provide enough power on the 3.3V and 5V you should be good. (For socket 7, you really don't need all that much - I'd expect 20A per line, 100W combined should be plenty - 25A on the 5V would give you a nice safety margin.)

gryffinwings wrote on 2020-06-04, 01:17:

@SodaSuccubus - Thank you for the advice, I wasn't sure if a newer PSU was safe due to the higher amps the PSUs provide.

You might be misunderstanding here - it's not that a power supply will provide more current. It's that it is able to provide more current. Actual current draw is determined only by how much power is currently being used by the components connected to the PSU.

The thing that's a problem is when you use a power supply with too small of a current rating. In that case, when the components in the PC try to draw more current than the PSU can provide, a cheap power supply might overheat or fail (possibly dangerously). A well made power supply will shut down to protect itself.

I just checked the SIV save files from one of my Socket 7 systems and for +5 15 Amps is more than enough even with 4 GPUs.

Have you thought about the power switch? When using a regular ATX case you need a different switch to keep the computer on as the normal ones only make contact when actually pushed and don't connect when released. AT power switch stays on when you push the button. (Sorry, what did you call or in English again?)

kepstin wrote on 2020-06-04, 17:36:

Some modern PSUs use DC-DC conversion to generate the 3.3V and 5V lines from the 12V internally. These PSUs do not need a dummy […]
Show full quote

gryffinwings wrote on 2020-06-03, 18:19:

I'm not seeing the ones that have the dummy load and give -5v. Does anyone know where to find the ones with the dummy load and -5v?

Some modern PSUs use DC-DC conversion to generate the 3.3V and 5V lines from the 12V internally. These PSUs do not need a dummy load on the 12V, since the conversion for the lower voltages is already putting a load on the 12V. Check power supply spec sheets and reviews for this feature - I personally use a Corsair CX series power supply in my Socket 7 (K6-III+) build.

As long as they can provide enough power on the 3.3V and 5V you should be good. (For socket 7, you really don't need all that much - I'd expect 20A per line, 100W combined should be plenty - 25A on the 5V would give you a nice safety margin.)

gryffinwings wrote on 2020-06-04, 01:17:

@SodaSuccubus - Thank you for the advice, I wasn't sure if a newer PSU was safe due to the higher amps the PSUs provide.

You might be misunderstanding here - it's not that a power supply will provide more current. It's that it is able to provide more current. Actual current draw is determined only by how much power is currently being used by the components connected to the PSU.

The thing that's a problem is when you use a power supply with too small of a current rating. In that case, when the components in the PC try to draw more current than the PSU can provide, a cheap power supply might overheat or fail (possibly dangerously). A well made power supply will shut down to protect itself.

Thank you very much for clearing up a lot of things, some of the information I was getting was based around the ATX2AT smart converter information:

https://x86.fr/atx2at-smart-converter/

So currently, my plan is to get an EVGA or Corsair PSU in the 400-500 watt range, I figured either one would do, and at least Bronze rated.

Sorry for the bump but I'm also looking into using a simple ATX to AT adapter for a 486 motherboard.

I was about to order one, until I saw this blog post about the 'smart converter' and his story about the overloaded 486 board. I have the board currently running with an AT power supply (but an ATX power supply would fit the case better), so can I be certain that there won't be any short/overload when using an ATX supply?

HandOfFate wrote on 2020-06-19, 10:57:

Sorry for the bump but I'm also looking into using a simple ATX to AT adapter for a 486 motherboard.

I was about to order one, until I saw this blog post about the 'smart converter' and his story about the overloaded 486 board. I have the board currently running with an AT power supply (but an ATX power supply would fit the case better), so can I be certain that there won't be any short/overload when using an ATX supply?

You can't be certain a short/overload will never happen whether using an AT or ATX PSU . A short can happen due to user error or, for example, due to a component failing on the motherboard .

The problem with ATX PSUs, as the SMART converter article explains, is that they can provide much more power than old AT PSUs. Consequently, if a short does occur, an ATX PSU will be able to provide much higher current than an AT PSU before the over-current protection kicks in . This can cause additional, possibly irreparable damage, to the component being powered .

The risk described in the article is something to keep in mind every time something is powered with a PSU that is vastly over-specced for it, not just when powering an AT mainboard with an ATX PSU .

A PSU will supply current current up to the limit set in its overcurrent protection circuit and a high current capable PSU will have that set higher than a less powerful PSU. This is by design and is inevitable if the high current PSU is to be able to actually provide the current it is rated for .

The smart converter provides a way to reduce the impact of a short by letting you set custom over-current protection limits that are closer to the max current needs of the motherboard that is used . This limits the potential damage caused by a short due to user error or motherboard component failure.

The smart converter will not prevent a component failure that causes a short but it will help limit the potential damage .

It is more annoying that some motherboards start beeping endlessly at the absence of -5V and have no BIOS options to turn that off than some cards requiring -5V to run properly. Those motherboards are the bane of my existence and the reason why I just stick to AT PSUs.

I hope that the ATX2AT Smart Converter will soon be released to be bought by anyone. I like the idea but unfortunately didn't read about it until recently.

darry wrote on 2020-06-19, 12:31:

HandOfFate wrote on 2020-06-19, 10:57:

Sorry for the bump but I'm also looking into using a simple ATX to AT adapter for a 486 motherboard.

I was about to order one, until I saw this blog post about the 'smart converter' and his story about the overloaded 486 board. I have the board currently running with an AT power supply (but an ATX power supply would fit the case better), so can I be certain that there won't be any short/overload when using an ATX supply?

You can't be certain a short/overload will never happen whether using an AT or ATX PSU . A short can happen due to user error or, for example, due to a component failing on the motherboard .

[...]

I see what you mean. I guess we always take some risk when powering on some old hardware (that reminds me, I should get aftermarket power supplies for my C64 and Amigas).

I might hold off on replacing that AT power supply with an ATX then, even though one of the ATXs I have is just 230 Watt. But I can always switch when that ATX2AT adapter becomes available, and deal with the AT power button situation (no place to mount it on this case) for now.

Marentis wrote on 2020-06-19, 17:17:

I hope that the ATX2AT Smart Converter will soon be released to be bought by anyone. I like the idea but unfortunately didn't read about it until recently.

Ah, good to hear! I was about to send him an e-mail but I will just keep an eye on his blog then 😀

HandOfFate wrote on 2020-06-19, 17:47:

I see what you mean. I guess we always take some risk when powering on some old hardware (that reminds me, I should get aftermar […]
Show full quote

darry wrote on 2020-06-19, 12:31:

HandOfFate wrote on 2020-06-19, 10:57:

Sorry for the bump but I'm also looking into using a simple ATX to AT adapter for a 486 motherboard.

I was about to order one, until I saw this blog post about the 'smart converter' and his story about the overloaded 486 board. I have the board currently running with an AT power supply (but an ATX power supply would fit the case better), so can I be certain that there won't be any short/overload when using an ATX supply?

You can't be certain a short/overload will never happen whether using an AT or ATX PSU . A short can happen due to user error or, for example, due to a component failing on the motherboard .

[...]

I see what you mean. I guess we always take some risk when powering on some old hardware (that reminds me, I should get aftermarket power supplies for my C64 and Amigas).

I might hold off on replacing that AT power supply with an ATX then, even though one of the ATXs I have is just 230 Watt. But I can always switch when that ATX2AT adapter becomes available, and deal with the AT power button situation (no place to mount it on this case) for now.

Marentis wrote on 2020-06-19, 17:17:

I hope that the ATX2AT Smart Converter will soon be released to be bought by anyone. I like the idea but unfortunately didn't read about it until recently.

Ah, good to hear! I was about to send him an e-mail but I will just keep an eye on his blog then 😀

Yeah, I heard these old C64 PSUs are killers when they fail .

If the ATX2AT Smart Converter is successful, I hope that a similar device for ATX to ATX connections could happen, just for the current limiting functionality . It would make me feel safer running my P3 off that 850W ATX PSU .

I'm sure the risk is there but meh. I still feel safer using a 500watt evga/corsair then relying on a used unserviced AT.

appiah4 wrote on 2020-06-19, 12:44:

It is more annoying that some motherboards start beeping endlessly at the absence of -5V and have no BIOS options to turn that off than some cards requiring -5V to run properly. Those motherboards are the bane of my existence and the reason why I just stick to AT PSUs.

My 386 mainboard act strangely unstable without the -5V, even the vga output become dark after a while and some I/O cards can't even boot the system.
So I've too the usual choice or the latest ATX v1.2 with the -5v line and the adapter -or- some AT psu in good condition I have but I can't decide. I'm trying this Enermax P4 ready v1.2 psu that's really extreme for a 386 (350W) but seems well built even if the number of wires is so high that the whole cable management is awful. In alternative the AT ones are shorter and with less cables but I still can't decide if is more a risk to have an old good much more complex ATX psu with the adapter or a much simpler but much older AT psu with less components. I'm sure both psu works ok but until when? I'd not like that one day as soon as I switch on the psu it smoke and break the whole connected system.