PDP-11 info needed.

What you are looking at is SDI (not to be confused with ESDI). Originally, it was designed to allow extreme distances between the disks and the controllers (up to 50', if memory serves). Subsequent designs were modifed to make it a pain in the rear. The one thing you must always remember about SDI - ALWAYS HAVE AN ODD NUMBER OF CABLES. They won't work if you don't. They're actually four coax cables in one sheath, and swap at each connection. Generally, there will be a cable from the drive to a block on the back of the cabinet, then the large black cables to go from box to box, then the red cables that connect the block to the controller. I don't know if there is a FAQ specifically about it, but there is some limitted info on the NetBSD hardware library. And yes, the UDA50 is the interface. I don't know about the Unibus version, but the Q-bus version (KDA50) is a dual-board set. Each controller can connect to four devices. Generally, most devices will have an A and B channel, which allows you to put the drive on two controllers for fault tolerance. If you need more cables or connection blocks, let me know. I just threw out about 10 dead SDI drives and have plenty of leftover cables. -- J. Buck Caldwell Engineer - Technical Support - Webmaster Polygon, Inc. email:buck_c@polygon.com phone: (314) 432-4142 PO Box 8470 http://www.polygon.com/ fax: (314) 997-9696 St. Louis, MO 63132 ftp://ftp.polygon.com/ bbs: (314) 997-9682