Leonard Erickson wrote in a message to JEAN PARROT:

 LE> Transfers between drives one the same IDE cable have to take turns.
 LE> Read from one drive into a buffer on the card, then write from that
 LE> buffer to the other drive. They have to take turns using the cable.

 LE> If they are on different channels, then you can read from one and
 LE> write to the other at the same time. 

They buffer on the card?  Jeez...

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