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Move the comment down to where appropriate

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Jonathan Campbell
2021-03-23 19:24:15 -07:00
parent 36a6d49587
commit e5e7c5e088
1 changed files with 15 additions and 16 deletions
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31
src/ints/bios.cpp
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@@ -9310,22 +9310,6 @@ public:
* and not a multiple of 32KB, things can break. */
if ((t_conv % 32) != 0)
LOG(LOG_MISC,LOG_WARN)("Warning: Conventional memory size %uKB in Tandy mode is not a multiple of 32KB, games may not display graphics correctly",t_conv);
/* Take 16KB off the top for video RAM.
* This value never changes after boot, even if you then use the 16-color modes which then moves
* the video RAM region down 16KB to make a 32KB region. Neither MS-DOS nor INT 10h change this
* top of memory value. I hope your DOS game doesn't put any important structures or MCBs above
* the 32KB below top of memory, because it WILL get overwritten with graphics!
*
* This is apparently correct behavior, and DOSBox SVN and other forks follow it too.
*
* See also: [https://www.vogons.org/viewtopic.php?p=948879#p948879]
* Issue: [https://github.com/joncampbell123/dosbox-x/issues/2380]
*
* Mickeys Space Adventure assumes it can find video RAM by calling INT 12h, subtracting 16KB, and
* converting KB to paragraphs. Note that it calls INT 12h while in CGA mode, and subtracts 16KB
* knowing video memory will extend downward 16KB into a 32KB region when it switches into the
* Tandy/PCjr 16-color mode. */
}
else if (machine == MCH_PCJR) {
/* PCjr also shares video/system memory, but the video memory can only exist
@@ -9343,6 +9327,21 @@ public:
}
if (machine == MCH_TANDY) {
/* Take 16KB off the top for video RAM.
* This value never changes after boot, even if you then use the 16-color modes which then moves
* the video RAM region down 16KB to make a 32KB region. Neither MS-DOS nor INT 10h change this
* top of memory value. I hope your DOS game doesn't put any important structures or MCBs above
* the 32KB below top of memory, because it WILL get overwritten with graphics!
*
* This is apparently correct behavior, and DOSBox SVN and other forks follow it too.
*
* See also: [https://www.vogons.org/viewtopic.php?p=948879#p948879]
* Issue: [https://github.com/joncampbell123/dosbox-x/issues/2380]
*
* Mickeys Space Adventure assumes it can find video RAM by calling INT 12h, subtracting 16KB, and
* converting KB to paragraphs. Note that it calls INT 12h while in CGA mode, and subtracts 16KB
* knowing video memory will extend downward 16KB into a 32KB region when it switches into the
* Tandy/PCjr 16-color mode. */
if (t_conv > 640) t_conv = 640;
if (ulimit > 640) ulimit = 640;
t_conv -= 16;