[Simh] VAX emulator slow to configure extra disks

[Paul Koning]

> On Jun 23, 2019, at 4:44 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
> 
> ...
> As Tim mentioned, some of the hardware that is modeled did indeed 
> allow arbitrary unit numbers (via plugs on the drive).  
> 
> Some 14 months ago support was added to provide per drive Unit plug 
> values to be set.   This is set via:
> 
>    sim> SET RQn UNIT=plug
> 
> plug can be any value from 0 thru 65534.  Default unit plug for each 
> RQn is n.

I know of 8 bit unit number plugs, in the RA series drives.  I haven't run into 16 bit unit numbers.

Some operating systems may limit the supported numbers.  For example, RSTS allows unit numbers 0 to 15 for MSCP disks.  And it supports multiple MSCP controllers, but the unit numbers must be unique -- unlike VMS which allows DUA0 and DUB0.

	paul