[cctalk] Re: Massbus emulation - UPDATE

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 >