Accessing a TK50 or TK70 from RT

Jerome H. Fine jhfinedp3k at
Sun Jun 12 10:19:38 CDT 2016

 >Rod Smallwood wrote:

>        Firstly one important fact that I did not know.  If you bulk 
> erase a TK50 you can turn it into a TK70 tape with an INIT.
>        Thank you I did not know that.

A bulk erase was the first thing that seemed to be the solution
since I had, fortunately, found a blank TK50 tape and was
able to use it to both read and write in a TK70.  There was
a long discussion, probably a decade ago, about CompacTape,
supposedly just for the TK50, and CompacTapeII, supposedly
just for the TK70.  From a Memorex internet site, probably over
10 years ago and long gone now, there was a table of all of the
physical characteristics of CompacTape.  While the tapes for
even higher density drives were different, the physical properties
of CompacTape (I) and CompacTapeII were IDENTICAL!!!!
So that also gave me the confidence to use the CompacTape
media in the TK70 drives - which gave excellent results.

Let us know if you are finally successful with the TK70 drives
and tapes.

>        Secondly I have made a little discovery.  We all know the tapes 
> go sticky and attach themselves to guide rollers etc.
>       Well its not always the tape.  I have three instances of tapes 
> that would not feed or lace up where I got rid of the problem
>       without doing anything to the tape at all.  In fact all 
> subsequent tapes have had no problems.   It took 30 seconds and
>       apart from taking the metal cover off the back off the drive I 
> dismantled nothing.
>       If I am right and can run a load of tapes through the drive. 
> Then I'll say what I did. If I'm wrong then nobody will needlessly try 
> my method.
>       I will say its not cleaning the heads or the EOT sensors. You 
> should do that any way.

It would be appreciated if you would state what you did in any case.
It is always helpful to know what has been tried and does not produce
a result since it can be ignored in the future.

>       Its clear the way to go is bulk erase TK50 tapes and then to use 
> the TK70 drive and controller.
>       Was there ever a UNIBUS TQK70 controller?

I never used Unibus, so I never found out.  YES!!  Bulk
erase is easy and does work well.

>      RX02 and a RX01 (I have one of each and a spare chassis)
>     I'll be back to them when this tape situation is sorted.
>     I had got to the stage where I could get commands through to the 
> drive electronics

I have an RX02 around which I have not used in a while.  My
preference, if I need the RX02 hardware is to use the DSD 880/30
which has an RX03 drive which can also function as an RX02 and
also reads and writes RX01 media as well.  My RX03 drive has
been modified by placing a DPDT switch into the detection circuit
for the single-sided vs double-sided sensors.  That way, I can use
any RX02 floppy media as double-sided without having to punch
the extra holes.  The DY.MAC device driver from V04.00 of RT-11
contained extra code to support double-sided operation, but that
code was no longer present with the V05.00 of DY.MAC when
it was released in 1983.  So I added the code back and that
made the DYX.SYS device driver under RT-11 able to support
double-sided RX03 floppies.  However, the boot code is still
a bit stupid and can't boot a monitor file which is partly at the
end of side 1 and continues onto side 2.

>    RD53 - Yes out of a bag of scrap drives I managed to get the 
> remains of a bump stop out and replace it.
>                 It produced one good drive which boots RT-11 every time.

I still have a few RD53 drives around which I stopped using.
I also converted a couple of Micropolis 1325 drives to
RD53 drives by adding jumper R7.  I really don't use
my PDP-11/83 very much since Ersatz-11 is really so
much more convenient and my goal for RT-11 is only
software bug fixes and enhancements.

Jerome Fine

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