DEC CPU bulkhead issues

From: Chuck McManis <>
Date: Fri Jun 23 16:02:20 2000

As some of you may recall, I was wondering about the compatibility between
the KA660 (VAX 4000/200 Q-Bus CPU) and the CPU bulkhead for a KA640
(VAXServer 3400 Q-Bus CPU).

My issue was that the on-board Ethernet (SGEC) on the KA660 wasn't able to
communicate through the AUI port on the bulkhead to the local LAN. (even
though the switch was in the correct position and the LED above the AUI
connector was green) The bulkhead had labels on it for a KA640 (indicating
that the CPU had been replaced) and so my first theory was that the
bulkheads were incompatible.)

The bulkhead is DEC part number 70-25775-01. And it classifies as an "S-type".

To debug this I removed the KA660 and inspected it, the SGEC is soldered in
so removing/replacing it wasn't an option. I installed a DESQA ethernet in
the backplane and netbooted NetBSD. I wrote a program to put the SGEC is
loopback mode and tested it that way, it works fine.

I scrounged around this morning and found another bulkhead with the same
part number and tried it instead. With this bulkhead the AUI connector
works! Yippee.

So, thinking that perhaps there is a fuse that is blown (this happened on
my DEQNA cab kit once before) I proceeded to disassemble the defective
bulkhead. However, there is no evidence of a fuse anywhere. So perhaps
there is a fusible link part. Anyway I'm hoping that someone on this list
has the print set for the bulkhead and can tell me what might be wrong so
that I might fix it.

Received on Fri Jun 23 2000 - 16:02:20 BST

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