Oldskooler Ramblings

the unlikely child born of the home computer wars

Dev journal, day 14

Posted by Trixter on May 14, 2014


1E            PUSH    DS
0E            PUSH    CS
1F            POP     DS
BEFFFF        MOV     SI,FFFF
B800B8        MOV     AX,B800
8EC0          MOV     ES,AX
FC            CLD
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4 Responses to “Dev journal, day 14”

  1. I guess you’re going to increment SI BEFORE MOVSWing your data? Otherwise you’re quite out of bounds of the CGA segment :P.

    • Trixter said

      I think you’re confusing SI with DI. But don’t worry, SI isn’t really FFFF either; it’s patched runtime by the compiler.

      • Yes, indeed I WAS confusing the two. I must be misunderstanding the context of the code, but from what I gathered, you’re about to do a write to the CGA segment.

        Curious why the compiler’s runtime included that mov to SI though if it doesn’t do anything.

        • Oh nevermind, I get what you’re saying now, ignore my second paragraph. SI’s real value isn’t determined until runtime as in “time to execute code”; I was thinking “runtime” as in the “C runtime library routines”.

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