5 Oct
2026
5 Oct
'26
7:25 p.m.
Hi Jim!
Just watched the video. Impressive no doubt.
Fitting it on the 3 5904 board would be perfect, Then it just sits there
in the RH11/RH70/Whatever and you don't need to deal with the ribbon
cables or a nice big MASSBUS bulkhead and cable.
I would love to keep an eye on this, thank you for doing it. Tape
emulation, specifically a TU45 with a TM03 with the 18 bit fiddler would
be optimal, but just getting the drive going would be a major step. We
can load the microcode off an RM03.
Chris
On 10/5/26 21:14, Jim Bender wrote:
Hi Chris:
Don't see why it wouldn't work on a 2020, but someone with a 36-bit
machine
will need to test it.
I think your expectations of the possible drive shrinkage factor are a
bit
off... :-)
While a solution that fits inside a terminator would be convenient, it
just
is not possible. You could, however, run ribbon cables directly from
the
Massbus transceivers (usually M5904s) to the emulator and hide the
emulator
inside the rack somewhere.
My eventual goal is to reduce the emulator to a three-board "sandwich"
that
takes the place of the M5904 trio on systems that use it. That
eliminates
the differential drivers and receivers and simplifies the electronics
quite
a bit. Also solves the problem of "where do I put the emulator at?"
:-)
Something like this:
https://www.dmv.net/mbe/RS06_Setasi.pdf
Jim
On 10/5/26 19:57, Chris Zach via cctalk wrote:
Jim:
Nicely done. If it runs on a 2020 this will finally be a
game-changer. :-)
Can it be built into a Massbus terminator plug? That would be a
proper mounting....
Chris
On 10/5/26 18:00, Jim Bender via cctalk wrote:
>
>
> It's been a while since my initial posting about this project but it
> is time
> for an update.
>
> This has been mostly a spare time project, and you know how life
> tends gets in
> the way sometimes...
>
> The work itself has been a bit of a "maze of twisty little passages,
> all
> alike" with many potholes and obstacles, but progress has been made.
>
> The video below tells the tale:
>
> https://youtu.be/KwaNschJg6w
>
>
> Synopsis:
>
> A real PDP-11/70 boots RSTS/E V10.1 through it's unmodified RH70
> controller
> with the data coming from the Massbus emulator.
>
> Operation is rock solid and so far have not been able to break it.
> It also
> passes the ERHAE1 XXDP diagnostic without errors.
>
> We now have a viable option for modern storage for Massbus systems.
>
> Still to do is performance optimizations, hardening against some
> edge cases,
> and a large amount of code cleanup.
>
> I only have a PDP-11/70 to test with, but it *should* work with any
> Massbus
> system. Adherence to the DEC Massbus Specification was strict and
> every
> attempt made to make it behave as a proper Massbus device rather
> than just
> coding things to make the RH70 happy.
>
> I am kicking around the idea of putting together a blog chronicling the
> various trials, tribulations and milestones encountered along the
> way if
> anyone is interested in reading the gory details....
>
>
> Cheers!
> Jim