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Some notes about porting DOSBox to systems with certain restrictions,
like handheld devices.
General:
- depending on where you start off with the port, assure that the
config.h entries are correct/exhausting, like GCC_ATTRIBUTE is
required (struct packing) but is undefined if you base the port
on msvc sources which have a special config.h
If memory is a constraint:
- in paging.h out-comment the USE_FULL_TLB define to enable special
TLB linking code that uses less memory
drawback: none (the code is not heavily tested though)
gain: reduces memory requirements about ~15mb
- in render.h lower the scaler integration:
#define RENDER_USE_ADVANCED_SCALERS 1
or
#define RENDER_USE_ADVANCED_SCALERS 0
drawback: complex scalers and the scaler cache are disabled,
be sure to test if this affects speed!
with define RENDER_USE_ADVANCED_SCALERS==0 most simple
scalers are disabled as well, some graphics modes won't
work due to reduced cache sizes
gain: ~2mb with RENDER_USE_ADVANCED_SCALERS==1
~5mb with RENDER_USE_ADVANCED_SCALERS==0
- in dos_system.h reduce the drive cache entries:
#define MAX_OPENDIRS 256
drawback: some apps might not work with large directory trees
gain: ~1mb per mounted drive
- remove the GUS emulation (gus.cpp, especially GUSRam[1024*1024] )
drawback: no gravis ultrasound
gain: reduces memory requirements about 1mb
- reduce the size of the emulated graphics memory:
see the memory sizing in SVGA_Setup_*, especially the defaults
in vga_s3.cpp's SVGA_Setup_S3Trio
drawback: some graphics modes won't work then
gain: reduces memory requirements
TODO: fully check this, introduce hard limits
If speed is a constraint:
- see if the simple core is faster, possibly remove the normal core
set the simple core as default
drawback: one game is known to not work with the simple core;
the simple core does only work for games which don't use paging
(when paging is requested the normal core is used automatically)
gain: the simple core should be somewhat faster
TODO: add possibility to easily remove the normal core, use fullcore fallback
- raise the default frameskip value
drawback: minor graphics smoothness loss for some games (video playback)
gain: reduces graphics load
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