PDP-12 at the RICM (Michael Thompson)

william degnan billdegnan at gmail.com
Sun Aug 2 09:44:01 CDT 2015

great news.  hope for further success.

On Sun, Aug 2, 2015 at 10:19 AM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
> 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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