PDP-11/45 RSTS/E boot problem

Jerry Weiss jsw at ieee.org
Mon Feb 11 12:13:09 CST 2019

On 2/11/19 11:50 AM, Paul Koning via cctalk wrote:
>> 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.
> 	paul
Though not a disk controller, the DEC DR11-B/DA11-B would not cross 64K 

I did however via a single chip "dead bug" modification, modify one to 
accomplish this.


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