> On Nov 23, 2015, at 1:00 PM, Johnny Billquist <b...@update.uu.se> wrote:
>
> On 2015-11-23 18:17, Guy Sotomayor wrote:
>>
>>
>> On 11/23/15 9:11 AM, Paul Koning wrote:
>>>> On Nov 23, 2015, at 10:10 AM, David Bridgham <d...@froghouse.org> wrote:
>>>>
>>>> ...
>>>> However, once we get a prototype doing something interesting, we were
>>>> talking about looking around for people interested in helping out.
>>>> We'll do a couple disk controllers but if someone wants to add others,
>>>> great. Especially if someone wants to add MSCP. We're happy to skip
>>>> that one ourselves.
>>> I can imagine. MSCP is a large effort.
>>>
>>> For a classic/straightforward programming interface, the Massbus disks
>>> (RP04 and successors) are a good choice. That will take you just over
>>> 500 MB, if you emulate the layout of the RP07.
>>
>> That's per-drive. Massbus allows for 8 drives per controller.
>
> Right. But then you also need to remember that there are some slight
> differences between different type of disks, meaning that in DEC parlance, if
> you have both an RP06 and an RP07 (for example) on the same massbus, it's
> called a mixed massbus, which not all OSes supported.
>
> As far as I can tell, disks fall into two groups, as far as massbus control
> is concerned. The RM02, RM03, RM05, RM80 and RP07 is one group.
> The RP04, RP05, RP06 is another. A few register addresses between the groups
> are the same, but the actual register at that address is different. But if I
> remember right, it's registers that have to do with error recovery, so
> potentially not something people would care about in emulation anyway. But it
> still means there are different drivers in the OS for them.
That sounds right.
RSTS/E supports mixed massbus, and supports RP07. At least in the sense of "it
definitely works". I don't think it shows up as supported in the
documentation, because as far as I remember the RP07 was not actually ever sold
as a PDP11 option. But it works just fine on a fast Massbus (one capable of
supporting an RM03 rather than just an RM02). In the RSTS/E development group,
there was an RP07 which I think was used to hold all the .LST files produced
during system build.
>
> And of course, you also have the TM02/TM03 and TM78, which have yet again
> different registers on the massbus.
Yes. And mixing disk and tape on a massbus is something that I don't think was
done on PDP-11s. It certainly could have been done, and it was on VMS and/or
TOPS if I remember right.
>
>> While, MSCP is interesting in that it's somewhat drive independent, it's
>> complex and it only really works with newer OS's.
>
> Well, "newer" in this case is sortof anything beyond the mid 80s. :-)
RSTS added MSCP support in V8, so if you want to run V7 you'll want to have a
traditional disk emulation.
paul
