I am going to buy some power adapters for a new ATX power supply to plug into an adapter to go to the AT motherboard but the ones I have seen on ebay only have two wires for the power button shouldnt there be an extra one? Also when I get the newer ATX power supply do I need to get one that has -5 volts for the ISA bus as all newer ones I know of dont have -5 volts.
wrote:I am going to buy some power adapters for a new ATX power supply to plug into an adapter to go to the AT motherboard but the ones I have seen on ebay only have two wires for the power button shouldnt there be an extra one?
Not sure what you're talking about. Post pics please.
wrote:Also when I get the newer ATX power supply do I need to get one that has -5 volts for the ISA bus as all newer ones I know of dont have -5 volts.
Yes you need -5v for the ISA bus. Some older ATX PSUs had it.
http://pinouts.ru/Power/MotherboardPower_pinout.shtml
The ATX Spec never outright banned -5v they just made it optional.
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wrote:I am going to buy some power adapters for a new ATX power supply to plug into an adapter to go to the AT motherboard but the ones I have seen on ebay only have two wires for the power button shouldnt there be an extra one? Also when I get the newer ATX power supply do I need to get one that has -5 volts for the ISA bus as all newer ones I know of dont have -5 volts.
The Power Switch connector only has 2 conductors.The intent of it is to use an ATX case and its soft power switch, one which only passes current when being pressed and is connected to the motherboard, with an AT motherboard, which has no power switch connector, and where the power switch actually controls the Power Supply.
For the -5V, it is not always required on AT motherboards. It is only required by specific ISA Audio Cards. In the event that you require it, you can either get an AT or early ATX PSU which provides -5V, or you can get one of the ATX to AT adapters which create -5V.
EDIT: To prevent future incorrect interpretation: The statement "For the -5V, it is not always required on AT motherboards." means that some AT motherboards do not require -5V, which therefore implies that some do. The statement "It is only required by specific ISA Audio Cards." means that there are certain ISA Sound Cards which require -5V to operate correctly, and that most do not.
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You can, as said, get an ATX psu with minus 5 volt. The wire is usually white.
Or you can buy adaptors that deliver minus 5 volt even though the psu has no minus 5 volt.
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wrote:The Power Switch connector only has 2 conductors.The intent of it is to use an ATX case and its soft power switch, one which only passes current when being pressed and is connected to the motherboard, with an AT motherboard, which has no power switch connector, and where the power switch actually controls the Power Supply.
The cheap Chinese adapters I've used only have two wires for power and these are just connected to the PS_ON cables and GND. This means it's non-latching, so if you connect the wires to a normal power button in an ATX case then the machine will only stay powered up while you're holding down the button - let go and it will switch off again.
You can either connect the wires to a traditional AT power switch (if the spade connectors will fit, or cut them off and fit your own), or in my case I bought ATX style power buttons in latching (toggle on/off) form. I replaced the power buttons in the case with these so the machine would stay powered up without having to hold down the power button.
The -5V is only required for some sound cards. But, why not avoid all that hassle and just use a regular AT supply? They're not that hard to come by or expensive.
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ATX is a better, safer design, as there's no line voltage going to the switch at the front of the case.
Also, as mentioned before, only a few cards explicitly require -5V.
ISA Cards & Devices Requiring -5V
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It is not correct to say -5v is only used in sound cards.
Advisors should refrain from assuming everyone else is using equipment within the limited range they personally tinker with.
-5v is also used onboard devices that utilize an ISA bus.
- That is true on some mobos all the way into socket 478. Those boards had no ISA slots but still used the bus internally.
-5v ISA has seen use in voice modems and some ISA based NICs.
-5v ISA has seen use in some specialized industrial add-in cards. One example is some ISA based O'scopes.
Certainly it's unusual to see -5v used outside of sound chips but that's not the ONLY place it was ever used.
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-5V is nothing a 7905 can't fix, that's how -5V is made in most PSUs I see also.
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wrote:It is not correct to say -5v is only used in sound cards. Advisors should refrain from assuming everyone else is using equipment […]
It is not correct to say -5v is only used in sound cards.
Advisors should refrain from assuming everyone else is using equipment within the limited range they personally tinker with.-5v is also used onboard devices that utilize an ISA bus.
- That is true on some mobos all the way into socket 478. Those boards had no ISA slots but still used the bus internally.
-5v ISA has seen use in voice modems and some ISA based NICs.
-5v ISA has seen use in some specialized industrial add-in cards. One example is some ISA based O'scopes.Certainly its' unusual to see -5v used outside of sound chips but that's not the ONLY place it was ever used.
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Agreed. DAC/ADC is easiest implemented using double ended supplies. Also, the thread I linked doesn't claim to be comprehensive, nor do I claim such. The peripherals listed do require -5V, but it certainly could be expanded with access to more hardware.
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wrote:-5V is nothing a 7905 can't fix, that's how -5V is made in most PSUs I see also.
I know it can be done I just never saw the point.
ATX PSU's with -5v are readily available and cheap (at least where I live) and I can rebuild them.
Additionally I bought 2 cases (20 PSUs) of brand new NOS (in factory bulk packaging) AT PSUs a couple of years ago.
I saw the lot at auction and figured I would future-proof myself a bit.
I haven't actually used a single one so I've been considering selling all but a few of them off.
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Half my ATX PSUs lack -5V, and not all the ones with -5V are very well built and when I make some old machine use an ATX PSU I sometimes have to add in a 7905 to get the nicest possible outcome with given hardware. No-cost solution when you already have the parts, ignoring time.
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wrote:Half my ATX PSUs lack -5V, and not all the ones with -5V are very well built and when I make some old machine use an ATX PSU I sometimes have to add in a 7905 to get the nicest possible outcome with given hardware. No-cost solution when you already have the parts, ignoring time.
That's reasonable.
I was just saying that for me it doesn't make any sense.
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GRUMPY OLD FART - On Hiatus, sort'a
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You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
Here is the adapter you need (also adds -5v)
https://www.ebay.com/itm/24-PIN-to-AT-P8-P9-C … DE/262868740795
This is the only saller on ebay that has these that I know of. I have bought quite a few different adapters from this seller. Good quality stuff.
I forgot I made this post sorry for not replying, I like the adapter from cyclone3d I will get one of thoes it has everything I am looking for. Thanks to everyone there was some good tips there, I mentioned a question about the power switch having 3 wires as when I last looked the power button from an AT power supply I have has 3 or 4 wires but now that ive seen the one on ebay from cyclone3d it clears that up.
