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Hacking the Hardware ("Choosy" software) 
written by N. Hacking / SUC/UK
Source: SUC-magazine March 1991, Volume 11 Number 1, p. 54  
Sharp Users Club - MZ-700 Section - Hacking the wares

“Choosy“ software shouldn‘t be a problem: when our data-recorders were split-new they had tight mechanisms, round pinch rollers and central capstans; the heads were perfectly aligned and the motors all ran at exactly the same speed. Under these conditions just about anything would work with one machine if it would work on another. Sadly, nothing lasts forever and some data-recorders will now be approaching their eighth birthdays... how healthy is the car cassette player that you bought in 1982? You can do something about head alignment, if you are adventurous you can even strip down the data-recorder and adjust its speed ( there‘s a pot on the control board ) but I doubt it will do much good; however, when the belts get slack, when the springs cease to be springy, when the capstan becomes eccentric and the pinch roller wears down to a sad oval shape it‘s time to put the old girl out of her misery. ( sounds like the wife, sub-ed ) Not only so old data-recorders become idiosyncratic - so that your machine can only swap software with a limited numbers of others - but they lose consistency. The signal that goes to your data-recorder is not reproduced faithfully on playback: in hifi terms, you are getting too much wow and flutter. At £9.00 ( from M&B ) replacement data-recorders have never been so cheap, and I doubt if they‘ll ever be so freely available again. Even if your recorder is healthy now, I count £9.00 as pretty cheap insurance for the future. It is, infact, possible to adapt a 700 and an “ordinary“ cassette player so that you can have motor sense / control. When recorders were £50 a shot I did it for one of my machines, but the built-in data-recorder is infinitely more convenient.

So, Paul asked, in an earlier issue, why he was getting check sum errors with his QD BASIC and not with S-BASIC. I have similar problems and did a bit of experimenting: Firstly, from what I can gather with my disassembler, S-BASIC uses a slightly different set of tape routines from those in the ROM monitor. ( BASIC has to worry about paging in the RAM from $D000 to $FFFF: the monitor doesn‘t ). QD BASIC uses a third set, different from the other two, and slightly less forgiving. One tape I was trying to TRANS was a commercial adventure that had obviously been recorded as an audio copy: a buzzing noise was audible with the tape eavesdropping switch ( see earlier issue ). I loaded this to S-BASIC and then saved it to the B side of the cassette: QD BASIC then accepted it quite happily, so that's one thing to try. This also ties up with Paul‘s own solution. ( I have no need for any other - sub-ed ).

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last updated September 12, 2003
SUC / UK: N. Hacking

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