Accessing a TK50 or TK70 from RT

js at js at
Sun Jun 12 13:18:49 CDT 2016

On 6/12/2016 12:00 PM, Rod Smallwood wrote:
> On 12/06/2016 16:19, Jerome H. Fine 
> wrote:
>> >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
> Thanks Jerome
>  Rod

Trim on long bottom posts, please.   
Especially if there's nothing 
interesting added at the bottom.

- J.

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