[Simh] RA70/73 simh support

[Tim Shoppa]

"Bob Armstrong" <bob at jfcl.com> wrote:
>   After a look at the source code, it appears that the only reason the RA70
> and 73 aren't supported is because some information about the drive
> geometry, notably the size of the RCT, isn't known.  Am I right about that?
> Is that all that's missing?

In fact very few OS's care about the exact MSCP mumbo-jumbo; most just want
a bunch of blocks and are happy with that. And in fact MSCP emulation
works just fine with an arbitray number of blocks on almost everything
except the real PITA OS's :-). It's not like we ever expect the disk
image to fail and for the OS under emulation to have to do the bad-block
replacement step-by-step. But in case the emulated OS ever wants to delve
into the RCT it's nice if it matches everything expected.

>   As it happens, I have a PDP-11 with two working RA70 drives.  Is there
> some XXDP diagnostic that will tell me the RCT size?  If there is, I'll be
> happy to run it and report the results.

Under RT-11, .SPFUN #373 can be used to access all the MSCP mumbo-jumbo.
A program that does so and prints it in a pretty manner is DUSTAT.MAC at

  http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/rt/misc/dustat/

Tim.