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