PDP-12 at the RICM (Michael Thompson)

COURYHOUSE at aol.com COURYHOUSE at aol.com
Sun Aug 2 09:59:48 CDT 2015

Congrats  Michael!
"This is the first time in 24 years that an OS has been run on this  
Ed# and crew at smecc.org 
In a message dated 8/2/2015 7:20:02 A.M. US Mountain Standard Time,  
michael.99.thompson at gmail.com writes:

With a  lot of help from Dave Gesswein and Warren Stearns we were able to
get the  MARK12 PDP-12 tape formatting program off a LINCtape and int paper
tape  format. Running it showed that a diode on the field-0 core stack had
failed  during the week making memory in the range of 4000-5000  unusable.
Fortunately we had a spare core memory stack so we were running  again in a
few minutes. We have traced and replaced diodes on core stacks  before, so
we will fix the broken core stack.

We were able to format  a LINCtape, but running it without a video display
was a little  challenging. The tape diags work better with the reformatted
LINCtapes, but  still not perfectly. It looks like there is an issue in the
selection logic  in the TU56. That should not be difficult to debug and fix.

We booted  LAPS6-DIAL from LINCtape. The VT14 display is not working yet, so
we were  driving blind. We could see some fuzzy characters displayed on  an
oscilloscope so we could see that our typing was actually getting  handled
by the editor. We tried three different oscilloscopes, but none  have an
intensity or blanking input so the display was not  readable.

We couldn't find any documentation for booting OS/12 from  LINCtape, so
Warren looked through an octal dump and found that block zero  is the boot
block, just like OS/8. The OS/12 boot block starts at 0020 like  many LINC
programs. Since this uses the serial console we were able to  interact with
the OS normally.

This is the first time in 24 years  that an OS has been run on this system.

Michael  Thompson

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