These lines provide kernel support for various filesystems and other options.
This line allows the kernel to simulate a math co-processor if your computer does not have one (386 or 486SX). If you have a Pentium, a 486DX, or a 386 or 486SX with a separate 387 or 487 chip, you can comment this line out.
Note: The normal math co-processor
emulation routines that come with FreeBSD are
not very accurate. If you do not have a
math co-processor, and you need the best accuracy,
I recommend that you change this option to
GPL_MATH_EMULATE to use the superior GNU
math support, which is not included by default
for licensing reasons.
Compatibility with 4.3BSD. Leave this in; some programs will act strangely if you comment this out.
ISA devices and EISA devices operating in an ISA compatibility mode can only perform DMA (Direct Memory Access) to memory below 16 megabytes. This option enables such devices to work in systems with more than 16 megabytes of memory.
Allow users to grab the console, useful for X
Windows. For example, you can create a console
xterm by typing xterm -C, which will
display any `write', `talk', and other messages you
receive, as well as any console messages sent by the
kernel.
This option provides for System V shared memory. The most common use of this is the XSHM extension in X Windows, which many graphics-intensive programs (such as the movie player XAnim, and Linux DOOM) will automatically take advantage of for extra speed. If you use the X Window System, you will definitely want to include this.
Support for System V semaphores. Less commonly used but only adds a few hundred bytes to the kernel.
Support for System V messages. Again, only adds a few hundred bytes to the kernel.
Note: The ipcs(1) command will
tell will list any processes using each of
these System V facilities.