Re: iigs: -5V, what for?

[dempson@actrix.gen.nz (David Empson)]

<martin.kaeser@auge.de> wrote:

> Hi,
> the Apple II used four voltages: +12V, +5V, -5V, -12V.
> The IIgs PSU supplies the same voltages, but are all four used?

They are all available on the slots, so must be provided for
compatibility with cards that need the negative voltages.

In addition, -5V and -12V are used as follows:

-5V is used in the final output stage of the video circuitry, and is
provided on the video connector.

-12V is provided on the disk drive connector.

-5V is used to power the transmitters for the serial ports.

-5V is provided to the Ensoniq DOC.

-12V is used to power several op-amps in the sound circuitry.

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand