DOSBox v0.72 - How to run resource-demanding games

DOSBox emulates the CPU, the sound and graphic cards, and other peripherals
of a PC, all at the same time. The speed of an emulated DOS application
depends on how many instructions can be emulated, which is adjustable
(number of cycles).
CPU Cycles
By default (cycles=auto) DOSBox tries to detect whether a game needs to
be run with as many instructions emulated per time interval as possible.
You can force this behaviour by setting cycles=max in the DOSBox
configuration file. The DOSBox window will display a line "Cpu Cyles: max"
at the top then. In this mode you can reduce the amount of cycles on a
percentage-basis (hit CTRL-F11) or raise it again (CTRL-F12).

Sometimes manually setting the number of cycles achieves better results,
in the DOSBox configuration file specify for example cycles=30000. When
running some DOS application you can raise the cycles with CTRL-F12 even
more, but you will be limited by the power of your actual CPU. You can see
how much free time your true CPU has by looking at the Task Manager in
Windows 2000/XP and the System Monitor in Windows 95/98/ME. Once 100% of
your real CPU time is used there is no further way to speed up DOSBox
unless you reduce the load generated by the non-CPU parts of DOSBox.
CPU Cores
On x86 architectures you can try to force the usage of a dynamically
recompiling core (set core=dynamic in the DOSBox configuration file).
This usually gives better results if the auto detection (core=auto) fails.
It is best accompanied by cycles=max. Note that there might be games
that work worse with the dynamic core, or do not work at all!
Graphics emulation
VGA emulation is a very demanding part of DOSBox in terms of actual CPU
usage. Increase the number of frames skipped (in increments of one) by
pressing CTRL-F8. Your CPU usage should decrease when using a fixed
cycle setting.
Go back one step and repeat this until the game runs fast enough for you.
Please note that this is a trade-off: you lose in fluidity of video what
you gain in speed.
Sound emulation
You can also try to disable the sound through the setup utility of the game
to reduce load on your CPU further. Setting nosound=true does NOT disable
the emulation of sound devices, just the sound output will be disabled.
Also try to close every program but DOSBox to reserve as much resources
as possible for DOSBox.
Advanced cycles configuration:
The cycles=auto and cycles=max settings can be parameterized to have
different startup defaults. The syntax is
cycles=auto ["realmode default"] ["protected mode default"%]
[limit "cycle limit"]
cycles=max ["protected mode default"%] [limit "cycle limit"]
Example:
cycles=auto 1000 80% limit 20000
will use cycles=1000 for real mode games, 80% CPU throttling for
protected mode games along with a hard cycle limit of 20000