No announcement yet.

OT Old time computer question...

  • Filter
  • Time
  • Show
Clear All
new posts

  • OT Old time computer question...

    Not really, really old like Hollerith days, but rather the dawn of the PC age, TRS80s et al.

    I have a couple of 'computers' from that era, very small Z80 jobs. Now the question is regarding the audio tape data storage.

    The idea is to write the data on a regular PC to a CD and play the 'data' back as audio for the antique to read, using a portable CD player.

    I know the data was written with a bit cell method but I dont know the exact format of the data.

    Anyone played with this?

  • #2
    Wow, I remember using those audio cassettes... Even as a 12 year old, it seemed like kind of a hack, but that may be because I was jealous of my friend who had an Apple II with floppy disk.

    Anyway, this guy seems to have some useful stuff:

    I just like to make stuff.


    • #3
      well many moon/eons ago I did a scratch build of a Zilog Z80 based computer which ran at 4 mzh and had 64 k of ram ( 4116 chips )

      anyway most of the audio tape interfaces were of the cuts type ,they used two tones high and low to record the data high = 1 low = 0
      therefore the data was sound hence the use of the audio tape.

      unless you know the frequency you will be in trouble.

      my build included a 8 inch floppy drive which I designed and built the interface and wrote the machine code to run it



      • #4
        I built a S100 system at one point, there were more than one system iirc the one I used was based on what the trs80 used. the encoding was based on NRZI.

        I used a SDLC chip, and iirc recorded the NRZI stream directly to the recorder. some where I have a notebook . . .



        • #5
          Originally posted by The Artful Bodger
          I have a couple of 'computers' from that era, very small Z80 jobs.....
          Would they be the Sinclair ZX-80?

          I still have mine from that era.
          Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
          ~Practitioner of the Electromechanical Arts~


          • #6
            Thanks Pete, that is a very good site and I will be going back there..

            Stuart, the tape modulation was quite simple I do know that as I have the circuit which was just two gate outputs and a resistor voltage divider.

            Fred, thanks, that what I needed to know, NRZI.

            Weston, VZ200 and VZ300. I have a cassette tape (which I hope is still good) with an assemblerand a bit of technical information. These little machines used the same tape format and I think much of the same firmware as the TRS80. Neither machine has a disk drive so it is all cassette tape.

            I am considering how I can do something useful with these but I well recall how patient one had to be to get a program to load from the audio tape, hopefully that would be glitch free if the sounds are digitally created and played on a CD player.


            • #7
              I think that this may be exactly what you need.

              Free software for calculating bolt circles and similar: Click Here


              • #8
                I had a TRS-80 Color Computer back then, and it read tapes pretty reliably. The dedicated cassette deck for TRS-80's had its frequency response tweaked to emphasize the upper midrange, as I recall. The bass was pretty well filtered out. It was a pretty standard portable cassette player except for that, and the omission of the microphone. When I first got the computer I tried using a regular cassette player and it had poor results, but the dedicated one was quite reliable. So I'm guessing that you'll want to limit the bandwidth of whatever source you substitute.


                • #9
                  Not sure about the creating new data on the PC part.....

                  As to the storage part.... I don't see why one couldn't route the output from the old PC's tape output into a soundcard and create a wav file containing your data. Once you created the file the PC could playback your new wav file into your old PC. Think of the PC system with a soundcard as an expensive cassette data recorder. With some sound editing sofware one could likely cleanup the data to make the transfer more reliable.



                  • #10
                    Ahh, old computers!

                    Over the years I've had (in no particular order);

                    Olivetti P652
                    Acorn Atom (two + floppy drive)
                    BBC B (about 6 + Music 500 + 6502, Z80 & 68000 co-processors)
                    BBC Master
                    Jupiter Ace

                    Back in the ZX81 days a friend managed to transfer programmes to another friend several houses away using a pair of FM trainceiver modules! He also had a 2K ram chip giving him 5 times the programme space!
                    Paul Compton


                    • #11
                      I did some piggybacking of chips in my ZX-80, doubling the onboard RAM.

                      In search of a genuinely useful application, I piggybacked a zero insertion force socket onto the system ROM chip and added a few logic gates to program 1702 EPROMS. Wow, took me a while to remember the 1702 - only 256 bytes!

                      Still have the little bugger.
                      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                      ~Practitioner of the Electromechanical Arts~


                      • #12
                        Lookie here:


                        • #13
                          I have one or more of each of these.

                          Free software for calculating bolt circles and similar: Click Here


                          • #14
                            Yeah, I've got a box full of Sinclair ZX-81 (and T1000) systems and parts, including a Wildonix eprom programmer and a bunch of ram packs. I still have the wirewrap expansion board I made too, and a bin full of eproms. No idea why I still have them. Sentimental I guess. Someday I'll browse Ebay, become totally disillusioned ... and then probably just bin them. Well, maybe I'll keep them until my kid gets old enough to complain about how slow his computer is... then I'll show him what I had at his age... he should get a good laugh out of that. 2K of RAM? 2K? My phone has 8 million times more!

                            You do know that you can emulate these systems on a modern computer, including downloading binaries - doing completely away with the audio cassettes? My little Nokia N810 Linux pocket computer even has an emulator for the Sinclairs, and the TRS-80, and ...


                            • #15
                              If there is anyone here that collects this sort of stuff I have half a
                              file drawer full of such.
                              A sort of list if of interest:
                              Timex 1000 , Commodore Plus 4 , TI 99/4A
                              All the manuals for the above.
                              Other booklets etc.
                              Mostek Z80 tech manual
                              ZX81 Basic programming, Assembly instructions, Software catalog.
                              SYNC special issue ( The magazine for Sinclair users )
                              Syntax ZX80 Vol 3 Nr 2 Feb 1982 (a pub of the Harvard Group )
                              Plus a bunch of misc schematics and interface info.