Looking for Tektronix 4051 programs... - test-drb@ccmp.vtda.org

27 May 2010

...
  Josh wrote: 
...
  I was working on software to dump 4051 tapes over a
serial port or the 
...
  GPIB bus, as well as an emulator.  Both are still
works in progress 
 (progress being very slow at the moment) based on disassembling the 
 system ROMs and going through the service manuals.  I recently came into 
...
  possession of the actual source code for the
4051's ROMs on microfiche, 
...
  which I've passed on to Al for archiving.  Looking
forward to reading 
 through those once he's done!

 I'm hoping that once I work out enough to write a basic emulation, I'll 
...
  know enough about the hardware to write some assembly
code for the real 
...
  4051 to allow raw dumps of 4051 tapes (and hopefully
writing them 
 back!).  But I have a few other things stealing time from me at the 
 moment, so it won't be in the near future...  

 I found some of my notes to "un-secret" the programs on the 4051.   You
need to load a string variable with 6800 program code and execute it to
clear the secret flag.   This is what I found:

You can execute at the command line:

L$="7?008039"

CALL "exec",L$

The string is code for the hexadecimal equivalent, where A through F is
replaced with a=":", b=";" c="<", d="=",
e=">", f="?"

Or the real hex codes are: 7F,00,80,39

Which represent the 6800 instructions:

CLR 00 80      ; clear memory at 0x8000

RTS               ; return from subroutine

I have one tape that came with the 4051 I recently acquired.  After
replacing the broken band I borrowed from another cartridge I have been
able to read parts of it.   It gets a read error part way through the
first file.    My question is, how long will old tapes and disk media
remain readable?   This tape was written about 20 years ago, and I have
tapes & disks for other systems that are much older.   Other than
keeping media in a cool, dry climate away from magnetic fields, what is
the best way to preserve them?   How long can the magnetic encoding
survive?