[Info-vax] RB730 Integrated Disk Controller (R80/RL02) usable with VAX-11/750?

[Bob Koehler]

In article <slrnis00n9.m6.rivie at stench.no.domain>, Roger Ivie <rivie at ridgenet.net> writes:
> On 2011-05-03, Bob Koehler <koehler at eisner.nospam.encompasserve.org> wrote:
>>
>>    IIRC, the 730 and 725 were true UNIBUS systems, using the UNIBUS
>>    as the system bus, with all its limitations, just like my PDP-11/34 
>>    and 11/44.
> 
> It's been a *long* time since I've used a /730, but I'm certain it had a
> UNIBUS map. I think the one I used to use had a couple megs of RAM.

   Yes, you can find a discussion of LARGO on the 'net, an 11/730 with 
   3 1MB memory modules.  Just because it's an 18 bit system bus doesn't
   mean the system is limited to 18 bits, you just have to get
   inventive.

> AFAIK, the only VAX without a UNIBUS map (or its equivalent) was
> MicroVAX I, which used QBUS memory and was therefore limited to 4MB.

   The 11/725 wasn't just a stripped down 730.  It's map would not
   automatically update at page boundaries, so drivers had to break
   down large transfers and update the map between pages.  (There's
   no way to be sure that successive pages in virtual memory are
   in the same part of the map in physical space.)