Why does my KDF11 cause spurious traps to 4??

From: Robert Armstrong <bob_at_jfcl.com>
Date: Sun Jul 18 23:43:46 2004

Hello,
 
  I've got a 11/23+ in a BA23 and when running RT11 I get spurious and
unexpected traps to 4. After while I noticed that it will do the same
thing while running the extended memory test built into the boot ROMs.
I pulled out all the cards except the CPU and the memory and it still
does it, and after swapping memory with another QBUS system that's known
to work I've pretty much come to the conclusion that it's not the
memory. Bummer - looks like the KDF11 is at fault.
 
  I actually cobbled the system together myself from an assortment of
cards and parts, so it's not unlikely that I did something wrong. Is
there any obvious mistake or mis-setting of the KDF11 jumpers that would
cause this, or is my CPU card hosed?
 
Thanks,
Bob Armstrong
Received on Sun Jul 18 2004 - 23:43:46 BST