ATA 66 pinout

[FrankL]

I want to connect two physical harddrives on the same cable (standard hook-up) except I want to add a switch to one or more wires in the cable to allow me to switch from one harddrive to the other (power off naturally). There was an adapter out on the market and was told it worked great simply by switching th control wire(s). They did not give any details.
Does anyone know what control wire(s) they were referring to? I think it might be one of four; DNA Request, I/O Ready, Cable Select, or IRQ Request. This is for an ATA 66 (80 wire cable).
If anyone knows, HELLLLLP.
Thank you,

[firyembers]

Connect both drives as CS on the 80 Pin Cable.

get yourself a double pole single throw switch,rate it at 5amps or so.
Cut and connect the supply 5v red and 12v yellow to the middle terminals.
take 5v and 12 v to one drive connector,then take 5v and 12 v to the other drive connector
Leave the blacks (Ground) connected directly to the drive connectors.
You will most likely have to extend the wires anyway so the switch will reach a convenient position on the case.

This is risky,if you are unfamiliar and suggest a friendly electrician to help,'cos if you mix up the wires the drives will be no more for sure,guaranteed.........
If you have multimeter to measure voltages check you have 5v and 12v in the correct places by comparing them with another drive connector most likely attached to the cd rom.
Go here to the lower portion of this article:
http://www.llamma.com/xbox/Mods/xbox_4_connector_ide_cable_udma_.htm

Or here
http://www.detnews.com/2001/techcolumns/0110/30/technology-330444.htm
Or here
http://www.dvhardware.net/modules.php?name=Sections&sop=viewarticle&artid=4
Now you have selectable drives,up for one drive and down for the other drive,shut down the pc before you switch.
I have used this way ok for two mates sharing one PC.
 
Hope this helps
Grahame