On Mon, Feb 4, 2019 at 3:15 PM Paul Koning via cctalk <cctalk@classiccmp.org> wrote: > > On Feb 4, 2019, at 3:43 PM, Noel Chiappa via cctalk <cctalk@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. -ethan
