VAX 11/750 boot probs - help appreciated

From: Matthew Sell <>
Date: Wed Jul 10 21:51:00 2002


I've finished restoring a VAX 11/750 back to good physical condition, and
have (by trial and error) selected a boardset that "appears" to be
operating correctly as far as I can tell.

The problem I'm having deals with booting from the integral TU-58.

When the machine starts up (set to halt on boot) - it presents the proper

00000000 16

Running the microdiagnostics gives no errors:

00000000 01

However, attempting to boot from the TU-58 (B DDA0) results in the
following message:


The strange thing is that the diagnostic LED on the TU-58 controller does
not respond as I would think it should. From what I understand of it's
operation, the diag LED on the controller is supposed to blink once when
power is applied, pause while internal controller diagnostics are
performed, and the light constantly when diagnostics pass (on the
controller). On mine, the LED blinks, and then stays unlit. But, if I
disconnect P2 (the communications cable to the 750 CPU), this controller
diag LED operates as expected.

This same behavior is observed if I remove L0004 in slot 4, then the TU-58
controller behaves as I have read it should.

This machine did have the remote diagnostics option installed, and I had to
move the TU-58 and console communication connectors to the alternate
position on the backplane as if the remote diagnostics option was not
installed. If I put these connectors back in the original positions (as if
the remote diag option was installed), the TU-58 controller passes
diagnostics, but the console does not respond (duh....).

Could the L0004 be sending a garbled request to the TU-58 controller? I
have tried two different L0004 boards, both exhibit the same problem. I
have tried different memory controllers to test the boot PROMs, and swapped
(and removed!) the L0008s, etc.


Any ideas?

 From what I understand of the installation of the remote diagnostics
module, the only modifications required were the installation of the board
(L0006), moving the TU-58 and console comm plugs to the left row of
backplane pins, and the installation of the modem.

Could I be missing another modification that needs to be "undone" ?

I really appreciate any hints or guidance.


         - Matt

Matthew Sell
On Time Support, Inc.
(281) 296-6066

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