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chitselb / pettil

6502 Forth-83 dialect for the Commodore PET 2001
http://pettil.tumblr.com
34 stars 3 forks source link

`STOP-UP` in editor new session crashes system #70

Closed chitselb closed 6 years ago

chitselb commented 6 years ago

apparently scr should not be a negative value. 0 max might help

The real fix for this is to allow block/scr/prev to be 16-bit unsigned for most purposes, pluggable VM for disk and SD-card etc.. support, and capping virtual-memory-on-cassette-tape(tm) at packet 255. Could maybe add a system user variable, VMOCT . VMOCT is the maximum # of packets available to vmbuf. When 0, VMOCT disables altogether that whole tape thing , which is what most C=64 users will want. Otherwise , and going up from packet 0 wraps around in a ring-buffer style to packet # VMOCT. This could also be used to implement 'shadow screens'

chitselb commented 6 years ago

solution: When scr becomes -1, add #vmbuf to it, wrapping around to the last screen. Since screen 0 can always be located by STOP-HOME this should improve navigation speed in the editor.

chitselb commented 6 years ago

fixed scr Thinking further, source can be loaded from screens, and screens can be loaded from any filesystem (including tape!). Since the reference machine is PET s/n 700251 with tape, that means disk block i/o support can wait for the C=64 port