Put the stub in both addresses? Best regards, Ed Johnson -----Original Message----- From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Gábor Lénárt Sent: Tuesday, February 07, 2012 8:31 AM To: CBM Hackers Subject: VIC-20 basic memory start + basic stub + etc Hi All, All we know the trick to use "basic stub" in our assembly projects (usually consist of a single basic line with a SYS). On C64 the behaviour is well known, the .prg itself starts with word $0801, etc etc. However, now I want to play with VIC-20. Now I have the situation that I don't really understand what address a basic prg will be loaded to. Also, I need plenty of RAM, so I am thinking about memory expansion first (well, to be honest it just mean some clicks in VICE - as I use emulator). But in this case: is it really true that load address will be different? Also, I've read that screen etc address may vary depending on the memory expansion. Now my question: can I write a program in assembly (with the basic stub) which works on both of unexpanded and expanded VIC-20 without any modification? Of course only, if the program would fit into the unexpanded VIC-20's memory :) But this means another question: if I have an expanded VIC-20 to the max (as far as I remember something like +28K RAM is reported by the basic startup msg) then will it be continous, that I can load a single prg file which is sized - let's say - 25K ? Now I've tried to save a simple BASIC program in VICE with max expansion and without it. The first word of the basic programs: unexpanded: $1001 expanded: $1201 Hmm, so according to this, it is simply not possible to do assembly projects work with and without memory expansions? (And I don't even count the case when video memory is at another location maybe ...) I'm thinking on writing some simple code (which contains only PC-relative jumps, etc) as the relocation code, which copies the rest of the code so I have a "fixed" address then for it, regardless of the memory expansion (but I will lose some memory then maybe about $200=512 bytes) to compensate the difference, and also I need to handle screen address not as a constant anymore ... Any suggestion is welcome. thanks, - Gábor Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2012-02-07 14:01:04
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