Oldskooler Ramblings

the unlikely child born of the home computer wars

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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

This entry was posted on May 14, 2014 at 9:57 pm and is filed under Demoscene, Programming, Vintage Computing. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

4 Responses to “Dev journal, day 14”

  1. William D. Jones (@cr1901) said

    May 20, 2014 at 8:46 pm

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

    Reply

    • Trixter said

      May 21, 2014 at 11:35 pm

      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.

      Reply

      • William D. Jones (@cr1901) said

        May 26, 2014 at 10:51 am

        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.

        Reply

        • William D. Jones (@cr1901) said

          May 26, 2014 at 10:53 am

          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”.

          Reply

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