flash (or ide) storage for unibus 11?

Johnny Billquist bqt at update.uu.se
Mon Nov 23 12:00:23 CST 2015

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 <dab at 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.

And of course, you also have the TM02/TM03 and TM78, which have yet 
again different registers on the massbus.

> 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. :-)


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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