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1

As I know it probably does not have any effect on the IRQ routine. Or does it? It does indeed: It allows other IRQs to be serviced. The 6502 I flag "masks" IRQs, and it is set automatically as soon as an IRQ is serviced and cleared implicitly by RTI. So, normally, IRQs are only ever serviced sequentially. By clearing the I flag yourself in an ISR (interrupt ...


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"Character memory" is the bitmapped definitions for each of the characters (e.g. "glyphs") that are displayed in text mode, based on the "character codes" that are poked into the "screen memory". Depending on which graphics mode you enable, there are several different memory areas that will be accessed by the VIC-II in creating the display. If we only focus ...


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Many Amiga games used hard coded addresses, for example to detect if extra memory had been installed by looking for it at specific locations. The introduction of floppy disks for storage also made multi-loading more practical. Most tape games tried to avoid it because of very slow load times, but with floppy disks it was common to load between levels. ...


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At least several answers (and comments) seem to interpret the question with an implied idea that one can have an assembler that does not resolve symbolic addresses. I think that this interpretation is misguided. In theory, yes, a program like this can be developed (there are some examples of such programs in the comments). However, in practice, starting with ...


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We certainly always used labels. There was interesting things done to reuse start up code as data. We were not above stealing buffers and things from the supposed OS but they still got labels. People also put variables into code which nobody seems to even know about any more. If you take Z80 then it's faster to do LD HL,constant than LD HL,...


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