Re: PDP-11/45 RSTS/E boot problem

[Paul Koning via cctalk]

> On Feb 11, 2019, at 1:13 PM, Jerry Weiss <j...@ieee.org> wrote:
> 
> On 2/11/19 11:50 AM, Paul Koning 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
>> 
> 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