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This will leave the maximum amount of memory free for use
as UMB space. For information on UMB space refer to
your DOS documentation, and the help files supplied with
your computer.
I/O ports
I/O ports are used by the processor to control the operation
of peripherals. Some expansion cards are controlled via an
I/O port or group of ports.
Which port or ports the card uses can normally be selected
on the card. Refer to the following table, and the
documentation supplied with the card to establish which
ports, if any, to use and how to select them.
Note
1. I/O ports are always given in hex notation. If you are
unfamiliar with this notation refer to Numbers and
computers earlier in this appendix.
2. If 10-bit I/O decode is selected in SETUP only ports 0 to
3FFh can be accessed on ISA cards. To access ports
from 400h to FFFFh 16-bit I/O decode must be enabled.
62
Free
I/O ports
(Hex)
100 - 11F
128 - 1EF
202 - 2F7
324 - 387
390 - 3B3
3B6 - 3B9
3D0 - 3D3
3D6 - 3D9
3DB - 3EF
400 - 51F
528 - 917
928 - FFFF
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