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Thread: TU60 TA8E / M8331 maindec and caps-8 questions

  1. #11

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    I wonder is these will work too...
    WTB: Case for Altair 8800 ...... Rolands Github projects

  2. #12
    Join Date
    Mar 2008
    Location
    Westchester County, NY
    Posts
    1,300

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    Folks,

    Sorry for being offline for so long. We've been working on our move from the NYC area to the Washington DC area.

    Indeed Mattis is correct that OS/8 works with the TA8E/TU60 as a non-system device. However, that is not a problem for making a CAPS-8 system cassette. To use OS/8 to make a CAPS-8 bootable cassette, one does not use BUILD as they are used to. Instead, you simply copy the files to a cassette that has first been ZEROed. Your OS/8 system head should of course have the TA8E handler INSERTed, or I think one can use MCPIP (I did the former.)

    The sequence of the files to be put on the cassette to make it bootable is critical. The first file must be the secondary loader, then second is the monitor. The remaining file order is not important. The TA8E bootstrap (either the one fat-fingered/MI8E'd into memor or the OS/8 BOOT TA) will read the secondary loader in to memory, which will proceed to load the monitor in off the cassette.

    It is important that cassettes used have clear leaders and have a hole/notch in the top approriate for a datacassette. Most of my original DEC TU60K media is unreliable, however I have had some success with more modern cassettes. I saved the clear leaders and housings from old cassettes and re-packed them with new tape. I found BASF (pre-EMTEC spinoff) tape to be the most reliable, however, even some recent Memorex tape was OK.

    And here is my post to alt.sys.pdp8 from 13 years ago when I first got CAPS-8 running again : https://alt.sys.pdp8.narkive.com/2ud...-original-iron. You will see that I built the bootable cassette the hard way. Back then I had very little hardware and no OS/8.

    In a fit of insanity some years back, I tried "playing" a TU60 datacassette in an audio cassette deck and digitizing the audio. At an 11kHz sampling rate (monaural, of course), I converted the audio to a raw data file. I made a crazy Excel spreadsheet that could process one block of data at a time, decoding the audio file, using the writeups in the manuals. It read the header and even verified the checksum. If there was tape dropout, you could look at the plot of the audio file and recover the bits by eye. It really did work and could handle the fact that "playback" of a Philips Compact Cassette used for audio has a constant 1-7/8 IPS tape speed while the TU60 which has no capstan, moves at varying tape speed (and therefore bit rate) depending on how much tape is on the the takeup reel. I made it while preparing to recover CAPS-11 Basic source tapes (which we recovered OK on the real hardware!) I will look for this file in the coming weeks and send it to anyone who is intersted. Recall that I am a mechanical engineer, so some things are brute force.

    Lou
    Last edited by Lou - N2MIY; August 14th, 2019 at 05:31 PM.

  3. #13

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    Hi Lou,

    Quote Originally Posted by Lou - N2MIY View Post
    To use OS/8 to make a CAPS-8 bootable cassette, one does not use BUILD as they are used to. Instead, you simply copy the files to a cassette that has first been ZEROed.
    Thanks a lot for your info! That sounds quite easy to do. But I still think it would be very nice
    to have a DumpRest version for the TU60 too. You never know what interesting kinds of tapes show up in the future.

    Quote Originally Posted by Lou - N2MIY View Post
    Your OS/8 system head should of course have the TA8E handler INSERTed, or I think one can use MCPIP
    That was one of my questions in general. How to add devices in an existing system. Not only the TU60, but also the TU56, RX01 etc...
    I hope someone can point me into the right direction on that...

    Quote Originally Posted by Lou - N2MIY View Post
    The sequence of the files to be put on the cassette to make it bootable is critical. The first file must be the secondary loader, then second is the monitor. The remaining file order is not important.
    Are these files on the http://simh.trailing-edge.com/kits/caps8_all.zip file usable on real tape?
    I wonder which files I need to put on the tape. What are the filenames of the secondary loader and from the monitor?

    Thanks for your help here!

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

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