strange number corruption on pdp11/34

Pete Turnbull pete at
Thu Jan 29 13:14:40 CST 2015

On 29/01/2015 18:32, Jacob Ritorto wrote:
> Johnny, you're insisting that I put in the real numbers for address and csr
> for testing the drive (for instance).  I'm going to do that next, here.
> But are you understanding that some of us think that the reason it prompts
> a zero default is that it's a manifestation of the zero bug and that the
> real value *is* actually safe but hidden in memory?  Did you see the
> RSX-11M crash dump I posted in the other thread?

I didn't see a crash dump, but did you see what I posted yesterday?

The default in XXDP for CSRs is very often zero, and I'm pretty sure it 
is so in the RL02 diagnostics (I've ont checked the listing for that 
particular one, but I did look at some others that were more readily to 
hand).  So when it asked you for input and you just hit "return", you 
really did tell it zero.  Applying the principle of Occam's Razor, and 
assuming the simplest solution is the correct one, you got a lot of 
zeros back because it was accessing memory instead of the controller you 

It's hard to believe you have a CPU fault that consistently prints 
numbers as zeros yet happily boots three different OSs.  Still, I'll 
change the tune if you re-run XXDP with sensible inputs.


Pete Turnbull

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