Posted By
Pigmy
on 2023-03-26
04:57:46
|  Re: Elite +4: Circle Closes
@Csabo: Wow, I didn't know these were all converted. My Plus/4 interest somehow passed in 1991 and I don't really know what happened after that. But Crown didn't even tell me he converted all those adventures in 1998, even though I was living in his flat at the end of 1998 when I moved to Budapest (or I forgot it meantime). I knew about Twin Kingdom Valley only.
Pigmy was frozen in 1991 and it's a time jump every time I switch back to him in a nostalgic wave  It's always 1991 in my head at such times and sometimes I am surprised.
Yesterday I thought I would have been happy to convert many of these if I had them, but there was no internet to just download them and I could reach only these. I liked converting them and I like complete collections of good things.
But you know what I talk about as I can see 
@MMS: the converted codes were always full of inserted JSR's - sometimes with a few NOPs following - at the critical parts where it was not enough to just overwrite some addresses. That subroutine had to replace the overwritten part and to solve the task that did not fit in the original code. It was a kind of brain surgery with a scalpel It was always a task to find an unused area in memory where all these hacking subroutines could take place after each other. That's why Battle Chess did not have sound at all because the memory was just full, I had to sacrifice something. The converted code was always longer than the original one because of these hackings. An other problem was calling ROM routines, because the +4 ROM used different memory addresses and buffers than the C64 one, and calling a ROM routine could screw up the game, overwriting used areas. Sometimes it was needed to save critical areas used by the +4 ROM to a safe place while calling it and to copy that area back after it returned. But in Elite there was a very small free place for that, that's why I had to put a turbo for tape I/O because it did not have to use the ROM routines. And the ROM generally was switched off, but it had to be switched on sometimes when needed, and this was always a critical part not only because of the used RAM areas but the IRQ routine that was possibly running in the RAM area under the ROM. But there were no general solutions, every game was different, that's why it was an exciting challenge if you can solve it.
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