11 Feb
2019
11 Feb
'19
9:50 a.m.
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:
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
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.