VOGONS

-5V for older systems

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First post, by AllUrBaseRBelong2Us

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It seems on both AT and older ATX psu's (20 pin connector), the white wire was the -5V lead. But modern ATX psu's (24 pin connector) omit the -5V. From what I've read, the -5V was important for the ISA bus. That said, my Pentium Pro has an ISA sound card and I'm running it off of a modern ATX psu that has no -5V rail. The sound card seems to work just fine. So when exactly is the -5V important?

Reply 1 of 3, by shock__

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LAPC-I requires that line to my knowledge.
When you have physical access to a card and have doubts, check if there are any signals/lines going from Pad B5 (5th pin near the slot bracket on the solder side) on the ISA connector - if that's the case it will require the -5V rail, which might be added to a system lacking that voltages.

http://pinouts.ru/Slots/isa_pinout.shtml

Current Project: new GUS PnP compatible soundcard

[Z?]

Reply 2 of 3, by QBiN

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I've started a new thread to try to document all the known ISA cards that require -5V as a resource for retro hardware fans:

ISA Cards & Devices Requiring -5V

Reply 3 of 3, by AllUrBaseRBelong2Us

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QBiN wrote:

I've started a new thread to try to document all the known ISA cards that require -5V as a resource for retro hardware fans:

ISA Cards & Devices Requiring -5V

Looks good. I plan on building a 486 soon, and I was going to use a modern ATX PSU w/ adapter, thus I'd have no -5v. I haven't bought all the components for the build yet, so I don't exactly know what video card, sound card, etc will be going in it. If I can pick and choose components that don't require -5v, then I suppose it won't be a big deal.

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