New PSU on old hardware - is the -5V rail important? \ VOGONS

New PSU on old hardware - is the -5V rail important?

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First post, by aurasdoom

aurasdoom Offline

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I have bought an old Pentium III Sony VAIO PC which came with a 120V PSU.

I replaced the PSU with a more modern one which doesn't have the -5V rail anymore. The computer complains about that at boot time. More specifically it thinks there's -12v on the -5v pin, but I checked and that pin is not present.

Did no computer ever use it and that's why it was removed?

Should I ignore it?

Reply 1 of 3, by Matth79

Posted on Today, 15:53

Matth79 Offline

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-12 being detected on the -5 is alarming, but that is presumably the voltage sense somehow floating - and if it's floating, then there is no load.
Some soundcards need -5 for the audio stages, and if you can spare an ISA slot, there is the "voltage blaster" https://www.philscomputerlab.com/voltage-blaster--5v.html.
In the AT era, it was needed a lot more

Reply 2 of 3, by aurasdoom

Posted on Today, 16:04

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Thanks for the reply. There is no ISA slot in this pc. Was it only used for those slots?

Reply 3 of 3, by mkarcher

Posted on Today, 16:22

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aurasdoom wrote on Today, 16:04:

Thanks for the reply. There is no ISA slot in this pc. Was it only used for those slots?

Since the 4116 memory chips (which required -5V if I remember correctly) were obsolete in 1983, Mainboards No longer required -5V, and the only remaining use was to forward that voltage to the slots.

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