Massbus - was: Re: VAX 11/750

[Rob Doyle]

On 2/25/2021 1:37 PM, Josh Dersch via cctalk wrote:
> On Thu, Feb 25, 2021 at 12:27 PM Al Kossow via cctalk <cctalk at classiccmp.org>
> wrote:
> 
>> On 2/25/21 10:43 AM, Chris Zach via cctalk wrote:
>>> Oh this is fun stuff. Is there a specification write-up anywhere on the
>> MASSBUS overall?
>>
>> there is some documentation on bitsavers
>>
>> the register descriptions were intentionally obfuscated to prevent cloning
>> that was figured out to make SIMH work
>>
> 
> Interesting... Is this obfuscation documented anywhere (beyond looking at
> SIMH code?)  I was working on an RH11/RPxx emulation for the Unibone that
> was partially working (and that I should really get back to...)
> 
> - Josh

I did a lot of reverse engineering of the RP06 and RM05 schematics.

The implementation in my KS10 FPGA passes all the DSRPA and DSRMB 
diagnostics that matter.  I didn't simulate all of the sector header 
hardware or ECC hardware since the disk already does that.

The register descriptions are at:

https://github.com/KS10FPGA/KS10FPGA/wiki/RPxx-Disk-Simulator
https://github.com/KS10FPGA/KS10FPGA/wiki/RH11-Massbus-Disk-Controller
https://github.com/KS10FPGA/KS10FPGA/issues/8

Rob Doyle.