American Megatrends 42 Series User Manual page 16

Step 1 Set Switch and Jumper Options,
J21 COM2 IRQ Select
J21 is a three-pin single-inline berg. Short pins 2-3 to select IRQ3 for COM2 (this is the default). Short pins 1-2 to select IRQ4
for COM2.
J23 Parallel Port IRQ Select
J23 is a three-pin single-inline berg. Short pins 1-2 to select IRQ5 for the parallel port. Short pins 2-3 to select IRQ7 for the
parallel port (this is the default).
J14 ROM Access 0 Wait State
J14 is a two-pin single-inline berg. This jumper is factory shipped with pins 1-2 jumpered for 0 wait ROM access.
J18 BIOS ROM Size Select
J18 is a three-pin single-inline berg. Short pins 1-2 to select 27256 ROM chips (this is the default). Short pins 2-3 to select
27512 ROM chips.
Selecting the Cache Memory Size
The setting of four-pin berg jumpers J50 and J51 and the presence or absence of an SRAM DIP in U32 control the cache size
setting:
Continued
Jumper/ For 64 KB
SRAM Cache
J50 OPEN
J51 OPEN
U32 PRESENT
For 256 KB
Cache
Short pins 1-2
and pins 3-4
Short pins 1-2
and pins 3-4
ABSENT