PDP-11 info needed.

From: Christian Fandt <cfandt_at_servtech.com>
Date: Tue Jul 7 16:41:53 1998

At 15:51 07-07-98 -0500, "J. Buck Caldwell" <buck_c_at_polygon.com> wrote:
>What you are looking at is SDI (not to be confused with ESDI). Originally,
it was designed to allow

Aha! That explains the handwritten marks on pieces of tape somewhere around
a couple of connectors and cables... it said simply "SDI".

>extreme distances between the disks and the controllers (up to 50', if
memory serves). Subsequent

Hmmm, if I have a space problem this may mean I could have the 11/34 in one
corner of my basement and the drive in a diagonal corner out of the way?
(about 20-25 feet)

>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.

Thanks for the description and that odd # of cables warning! This sure
helps a bit.

>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.

Thanks for the offer. I'll keep this on file. And thanks very much for the

Regards, Chris
-- --
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA
Member of Antique Wireless Association
        URL: http://www.ggw.org/freenet/a/awa/
Received on Tue Jul 07 1998 - 16:41:53 BST

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