[Simh] EXT : Questions regarding future simulator development

[Larry Baker]

On 10 Apr 2013, at 11:22 AM, <simh-request at trailing-edge.com> <simh-request at trailing-edge.com> wrote:

> 2> Assuming that the MASSBUS hardware devices actually supported the extended configuration, you could certainly add the extra components into the configuration. The question then becomes do any of the operating systems that ran on the original hardware support the extended configuration? If the operation systems don't support the extensions, then adding the extra simulated components is a waste of time. Otherwise, you just have to ask yourself "Is it worth the effort?" Note that any new components added to a simulation should be disabled by default for compatibility with older scripts.


RXS-11M-Plus did a very nice job of supporting multiple MASSBUS controllers.  Not only that, it supported mixed-MASSBUS configurations -- tapes and disks on the same controller.  And, multi-path MASSBUS configurations to dual-port disk drives.  Our PDP-11/70 had several MASSBUS disk drives all dual-ported to two MASSBUS controllers.  RSX-11M-Plus issued seeks separate from data transfers.  Whichever controller was available could be used to issue any command to any drive it could reach.  As I recall, the PDP-11/74 could have even more than 4 MASSBUS controllers, because each processor had its own MASSBUS/UNIBUS.  Some rather powerful disk configurations could be configured.  RSX-11M-Plus had all the code to make it work.  (The developers used a PDP-11/74 system.)

Larry Baker
US Geological Survey
650-329-5608
baker at usgs.gov

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