2 Feb
2010
2 Feb
'10
4 p.m.
We had an 11/45 ( as I recall) at the U of Illinois that was said to be the
longest unibus in the world. It had 2 DB11 repeaters on it, and there was
talk or putting on a third. I can't remember how many bus loads were on
there, but this sys was loaded.
Paul
On Tue, Feb 2, 2010 at 12:36 PM, Jack Rubin <jack.rubin at ameritech.net>wrote:
As I slowly dig into "my" new 11/34A,
I'm amazed by the bus configuration.
Starting from the CPU, the main BA11 chassis has a double (9-slot) system
unit, joined to a single (4-slot) SU by an M9202 jumper. From the last slot
in the chassis, a Unibus cable runs to a junction block on the cabinet back
door. A second cable runs from there to a remote BA11, also with 2 SUs. A
third cable runs back to the rack door/junction block (labled "bus station",
BTW) and finally a fourth cable runs to a small rack mounted I/O box with a
single SU and an M9302 terminator in the last slot. Cable runs must be about
20-25 feet total.
At first, I was worried that the length was too long (though it was a
working system in use for several years) but after a quick websearch (
www.psych.usyd.edu/pdp-11/unibus.html), I see that the bus can be up to
FIFTY FEET before a repeater is needed. My short term plan is to pull all
the cables and move the 9302 into the system box for testing. Now I'm
worried that the bus might be too short - do I need to look for one of the
"new" jumpers with two feet of cable or should it work with my old M9202
jumper block?
Jack