11 Feb
2019
11 Feb
'19
10:29 a.m.
On Feb 11, 2019, at 1:13 PM, Jerry Weiss <jsw at
ieee.org> wrote:
On 2/11/19 11:50 AM, Paul Koning via cctalk wrote:
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
That's rather shocking. I meant my comment to apply to every DMA controller, not just
disks. I never used the DR11-B, though. Perhaps there are other obscure devices that get
this wrong. But, for example, even devices like DMC-11 and TS-11 got it right.
There are of course Q-bus devices that only do a partial address space, but my point is
that whatever the number of address bits implemented, address arithmetic is as a matter of
normal design done across all of them, not across a subset.
paul
...
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