Board
Section 2
BIOS setup
System Speed
The two options are: “Low” and “High.” Selecting
“High” will run the system board at the maximum
clock speed, i.e.
The “Low” option will run
the system board at
This option is useful for
debugging problems or running speed sensitive
software.
Exception Trap
This option is used to enable or disable a feature in
the Mylex BIOS that traps illegal instructions made
by software programs. When this feature is en-
abled, errors will be trapped and the location in
memory where the error
will be displayed
in hex. With this option disabled, the system may
either ignore the instruction or hang depending
upon the circumstances. For more information re-
view Appendix A in this section.
Primary Cache
This option may be used to enable or disable the
486’s internal cache memory.
Secondary
Cache
This option may be used to enable or disable the
external cache on the
Block 1
Because certain expansion boards have shared
memory, that is memory used by both the adatper
and the system board that resides on the adapter.
This option was provided to ensure compatibility
with these expansion boards.
If an expansion
board that uses shared memory addressing above
1 MB (decimal) is installed, use this option to disable
caching this memory area.
For example, an adapter board such as a frame
grabber that uses
of shared memory is in-
stalled at
(decimal). The Non-Cache Block
1 should be enabled. The size of the non-cache
block should be set at 512K and the base address
of the non-cache block should be set at
(Note:
Except normal video memory addresses,
memory in the 384K “shadow zone” between 640K
and 1 MB is never cached.)
10
Version DO1
Copyright 1993
