ISO: PDP-11/40 LTC and Stack Limit options

Guy Sotomayor Jr ggs at
Tue Nov 22 19:13:06 CST 2016

> On Nov 22, 2016, at 4:40 PM, Josh Dersch <derschjo at> wrote:
> So... maybe I just completely missed the memo on this, and maybe there's still something wrong with my backplane... is it possible that slot 9 of the 11/40's CPU backplane is wired *specifically* for an M7800?  I guess I need to spend some time tonight seeing what the differences are... but now I need to go attend to a cranky 2yo who just woke up from a nap…

I seem to recall something similar with one of the 11/40’s I was working on.  I believe that because the 11/40 CPU backplane is wired for an M787 that things don’t work quite right if you try and install an M7856 into the SPC slot in the backplane and try and use it and not the M787.  There is a way to jumper the CPU backplane so you can use na M7856 and not the M787.  I haven’t really investigated it in detail (and it’s been a long time since I messed around with the 11/40 at that level).

TTFN - Guy

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