It's around at some sites but I thought I'd post it anyway.
To use a ATX power supply in some Macs the /PFW Power Fail Warning
Mac pin needs to be inverted and connected to the ATX PS-ON pin.
This will work in old 68k macs like MacII's as well as PPC macs.
Any mac with a /PFW Power Fail Warning pin should work.
The /PFW Power Fail Warning pin goes high when the mac is switched on
but the ATX PS-ON pin needs to go low.
Also connect the +5v in the pict to the ATX Stand By pin.
All other connections like the +5v +12v etc are straight forward.
If you use a Cmos 74HCT04 instead of the 74LSO5 you don't need
Here is a transistor based invertor