Massbus - was: Re: VAX 11/750

John H. Reinhardt johnhreinhardt at
Fri Feb 26 08:48:18 CST 2021

On 2/26/2021 8:40 AM, Lars Brinkhoff via cctalk wrote:
> Toby Thain wrote:
>> Rich Alderson wrote:
>>> You could ask our friends Keith Perez (Massbus Disk Emulator v1) and
>>> Bruce Sherry (MDE v2) about it, or even ask me.  ...  produced, and
>>> we had to do something.  My brilliant friend Keith sat down with a
>>> logic analyzer and an RP06 attached to a KL-10, and proceeded to
>>> spend the next two years (when not called on for other projects)
>>> creating a disk emulator. ...
>>> Later, Bruce came on board as the museum was ramping up, and redid
>>> the design in a Xilinx chip with VHDL. ...
>> Are the above projects published?
> See here:
Also here is Rich's announcement on DEC-10 day of 2017

> Happy DEC-10 Day!
> It is my honor to announce that we at Living Computers: Museum + Labs
> are releasing to the computing community our Massbus Disk Emulator
> and all the associated software.  This device connects via Massbus
> cables to the RH10 and RH20 interfaces on KI-10 and KL-10 systems, to
> the RH11 interface on KS-10 and small PDP-11 systems (including the
> front end 11/40 on the KL-10), and to the RH70 on the PDP-11/70.  The
> MDE provides up to 8 emulated RP06 or RP07 disks (represented by disk
> files in the format used by the SimH emulation of these systems).
> We expect that it will also work with the RH780 on the VAX-11/780 and
> VAX-11/785 although we have not yet tested it in this configuration.
> The original MDE was designed by Keith Perez in 2005, and emulated up
> to four RP06 drives connected to a KL-10.  The current generation was
> a redesign by Bruce Sherry in conjunction with the restoration of our
> DECsystem-1070 in 2012, and initially provided eight RP06 drives on
> the RH10.  It has undergone continual development, with associated
> software created for us by Bob Armstrong, and is now being opened up
> for the use of the relevant communities.
> To this end, we have placed the design files for the hardware and the
> source files for the software to interface with it, along with our
> library of Universal Peripheral Emulator routines, on public access
> repositories at Github.  The URLs for these repositories are
> These are released under a very liberal license which will allow for
> free use of the MDE by any interested party.
> Happy Dec-10 Day!
>                                                                  Rich
> Richard Alderson, Sr. Systems Engineer
> Living Computers: Museum + Labs
> 2245 1st Avenue S
> Seattle, WA 98134
> Cell: (206) 465-2916
> Desk: (206) 342-2239

John H. Reinhardt

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