PDP-11/45 RSTS/E boot problem

Paul Koning paulkoning at comcast.net
Mon Feb 11 11:50:56 CST 2019

> On Feb 11, 2019, at 11:12 AM, Jon Elson via cctalk <cctalk at classiccmp.org> wrote:
> On 02/11/2019 07:04 AM, Noel Chiappa via cctalk wrote:
>> A look at the RK11 registers after the swap-out showed an anomaly; something
>> about the extended memory address bits? (Maybe a multi-block transfer than
>> crosses a 64KB boundary? That would explain the address sensitivity we were
>> seeing.) Hopefully he'll track it to its lair shortly.
> OH, BOY!  I think you may have found it.  Likely some disk controllers did NOT SUPPORT crossing 64K boundaries!  The diags would not detect that, as it was likely expected behavior.  I would suspect the driver would need to break up these operations.

You may be thinking about PC controllers like the floppy controller.  I can't remember ANY DEC DMA device controller that had boundary crossing limits of any kind.  It certainly isn't a restriction in the RK11.


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