Help with my PDP 11/73

From: Ethan Dicks <>
Date: Mon Feb 17 16:44:00 2003

--- wrote:
> OK!!!
> The null modem that I just bought
> must have been bad. I got another
> one from a different vendor and I
> can talk to my processor.

Good start.

> I am able to get into dialog mode,
> setup mode, and into ODT.


> I runs the self test loop correctly.
> However, when I try to boot
> either DU0 or MU0 the machine gets
> hung up.

Do you have a complete grant chain? Gaps in the backplane
will also cause that behavior. You need all the cards "next"
to each other (according to the routing of your grant signals
which differs, depending on which backplane you have).

If you have a BA23, your grant goes something like this...

1 A-B
2 A-B
3 A-B -> C-D
4 A-B <- C-D
5 A-B -> C-D
6 A-B <- C-D

...etc., down to slot 9. Other backplanes are different (some all
sinusoidal, some straight down).

> My assumption is that the disk may have been erased before
> sale and the tape cartridge I got is probably blank.

Possibly. If it just hangs when you boot to MU0, though,
without moving the tape, it may not be the media.

No way to tell about the disk at this stage.

> Where can I get a copy of XXDP on
> a TK50 cartridge? Or is there another
> way I can determine if my two peripherals
> are working?

Don't know. You _might_ be able to find XXDP on RX50 media
(or at least disk image files of the RX50 media), but it sounds
like you don't _have_ a floppy drive on your machine.

Received on Mon Feb 17 2003 - 16:44:00 GMT

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