[Simh] Questions regarding future simulator development

[Mark Pizzolato - Info Comm]

On Thursday, April 11, 2013 at 1:37 PM, Johnny Billquist wrote:
> On 2013-04-11 22:14, Mark Pizzolato - Info Comm wrote:
> > On Thursday, April 11, 2013 at 7:00 AM, Bob Supnik wrote:
> >> 1. Four Massbus channels on the PDP-11 (or VAX). This is straightforward.
> >> The RH simulator already supports two, and the extensions from two to
> >> four use the existing mechanisms:
> >>
> >> - add the register blocks definitions to the header file
> >> - define additional RHC, RHD devices with matching unit and register
> >> definitions
> >> - look for places where "2" is hardwired as the maximum number
> >> - modify the autoconfiguration table for the additional device
> >> addresses
> >
> > This is most of it, but additional devices and units must also be defined in
> the pdp11_rp and pdp11_tu which then need to be connected to the new
> RHC and RHD devices created above.  Maybe a way to dynamically assign
> particular rp or tu devices to  a particular Massbus is also be necessary
> (someone might want 3 disk controllers and 1 tape, while others might want
> 3 tape and 1 disk controller, etc.).  If mixed configurations are possible
> something needs to validate that there are no Massbus conflicts.
> 
> Isn't there already? I mean you should not be able to attach two different
> disk drives with the same unit number. And that is the only kind of conflict
> you can have.
> 
>  From an RSX point of view, even having an RM and an RP disk on the same
> Massbus is considered a mixed Massbus. Like I said before. RM and RP are
> not the same from the host point of view, and should most likely not be
> considered the same from simh point of view either. But that is another
> issue.
> 
> Conflicts, as such, can only be about the unit number.

Ignoring mixed massbus or not and the details of what unit the OS refers to a device as, the current pdp11_rp device is structured to have a total of 8 disk drives.  These 8 drives can be a combination of RP or RM drives.  The real goal of this exercise (what I believe the original poster was asking for) was to expand the number of total RP and RM disks which the guest OS can have access to.  I'm pretty sure that such an expansion would take more than expanding the unit array sizes in the pdp11_rp code.

- Mark