[Simh] RP/RM differences in header commands (for ITS, salvager)

[Rob Doyle]

On 6/26/2019 9:54 PM, Lars Brinkhoff wrote:
> SALV actually writes data for an entire track all in one go.  I tried
> something which skips the headers in the middie.  But there must be
> something else wrong with my code, because when reading back the sector
> data I just get zeroes.
> 
> Anway, I agree something like that would go most of the way to make SALV
> happy.  There's another part of SALV that reads the header information
> go access the pack number written there, but I'm not sure how that
> number is used later.

I think that should work. When executing the "write header plus data"
command, the state machine in my FPGA's RP06 controller just handles the
first two 36-bit words (technically four 16-bit words) specially and
jumps to the "write data only" states to transfer the non-header data.
Ditto read and write check commands.

This part of the FPGA passes all of the RP06 diagnostics - so I believe
it is correct.

 From a hardware point of view, sector header "Word 3" and "Word 4" have
no particular meaning.  Just for completeness, can you point me to a
reference where "pack number" is defined or used by the software?

Rob Doyle