Posted By
TLC
on 2010-04-09
14:19:37
|  Re: Interesting project
Gaia: actually, MegaCopy V1.1 is "not" a Her Turbo descendant... it's rather a descendant of György Rétvári's C64 compatible turbo (the one whose listing you have found in that '86 Mikro Magazin  ie. http://pcvilag.muskatli.hu/irodalom/mm/86/86112/kep.php?kepparam=m86112-5.jpg ). That's also the very reason of it successfully cooperating with "full-wave" TAP files (unlike HER, which sometimes breaks the rules implied by original full-wave TAP and can only be stored successfully in half-wave TAP files). As for the speed -- it's as fast as the usual C64 turbo tape format is. It's somewhat faster than HER, whose principle is similar to the method used here (...I'm wondering if the creator of HER Turbo had known C64 turbo tape routines previously to coding his routine), but the timing is shorter ie. the bitrate is higher. You can get an idea of how "fast" it is of the width of the color bars during load... one color bar is one byte... (that may make it something like 4-5 character rows per byte (strongly depending on the number of 0 and 1 bits, one of them takes longer as this is just pure FM encoding), ie. 6-7 bytes per frame... ie. around 300-350 bytes per second). ...I do remember of modified HER Turbo versions (none that I could have got hold of back in the time but whose recordings I used to receive from friends with whom I swapped stuff) whose timing has been tuned up similarly or just in a similar fashion.
The strong influence of Tape Messiah to MegaCopy is obviously a result of some level of envy :-D. It was a so enhanced and nice program, but I had "problems" with it (I had no floppy drive at the time) that I couldn't work around, nor could I (obviously) cure, being it (for me at the time) a relatively complex program (...and on top of that, it resided in the color and screen ram, making it pretty hard to test and being capable of list/edit it concurrently). I was also dissatisfied with the speed of all the turbos that I could get hold of, including Tape Messiah. From the other hand, there was this C64 compatible turbo, which was completely useless by itself but which also turned out to be relatively (very) fast in simple tests that I arranged. ...I disassembled it and extracted parts that I believed to be the "core" of the load/record processes (...I obviously didn't know how the "hell" tape recording should work (at all) at the time, I didn't even know that tape recording "works" through writing and reading values from the processor I/O port at $01... those were the days... :-D ). I knew what I should "support" at the end ie. what features of Tape Messiah should be "kept" at all costs (because they just ruled), together with this fast recording format and the other details that I missed and couldn't work around in TM. ...And that's what came out. Support for the extra short Kernal header was done "through" reading the Kernal disassembly and experimenting. The turboload routine could just "barely" fit in the tape buffer, it had to be re-written, even after that there weren't any free bytes left in the buffer... Support for autostart, disabling autostart on files (to be copied) and other stuff was also added by/after experimenting.
(Hmmm... Why did I write all that down now, anyway?... )
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