PDP-11/45 RSTS/E boot problem

Paul Koning paulkoning at comcast.net
Mon Feb 4 17:18:53 CST 2019

> On Feb 4, 2019, at 5:47 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
> On Mon, Feb 4, 2019 at 3:15 PM Paul Koning via cctalk
> <cctalk at classiccmp.org> wrote:
>>> On Feb 4, 2019, at 3:43 PM, Noel Chiappa via cctalk <cctalk at classiccmp.org> wrote:
>> That translates into "the problem depends on the physical address of the code being executed".
>> The obvious answer is bad memory.
> At the board level, yes.  Deeper, it could be bad memory bits or bad
> memory decode.
> A simple ones-and-zeros test can identify bad DRAMs.  It's not as
> likely to find bad decoding, which could result in the same chips
> tested more than once and other chips not tested at all.  I've found
> both problems in real MS11-L boards I have for my stack of 11/04 and
> 11/34s I'm testing.
> ISTR in the DEC world, they were good about that.  I have multiple
> papertapes for the PDP-8, that I think were literally called "ones and
> zeros" and "memory address" tests.  I would think XXDP has something
> similar in terms of progressive tests that expect the previous stage
> passed.

Yes, one of the standard early PDP-11 memory tests is the "no duplicate address test".


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