These are the original drives from Vortex, for use on CPC 464. The hardware supports one or two 80 track drives, additionally a 3" [[Amstrad Disk Drive|FD-1]] can be connected as third drive, ie. unlike most other CPC disk interfaces it supports more than 2 drives. [[VDOS]] allocates RAM for only 2 drives though, which of the 3 drives are in-use is selected with |S command.
|S,0 - 3rd drive is ignored:
|S,0:|SELECT,"A" - access 1st drive
|S,0:|SELECT,"B" - access 2nd drive
|S,1 or |S,2 - choose if 'A' or 'B' is 3rd drive. i.e. Decide if |A is 1st drive or 3rd drive or |B is 2nd drive or 3rd drive.
|S,1:|SELECT,"A" - drive A is 3rd drive.
|S,2:|SELECT,"B" - drive B is 3rd drive.
== Vortex -Z Drives (180K/side or 180K/disk?) ==