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X-Hacker.org- CA-Clipper/ExoSpace 1.0g - <b>pc/at compatibility</b>
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PC/AT Compatibility
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CA-Clipper/ExoSpace works on all IBM PC/AT-compatible computers. There
are, however, some machines that claim AT compatibility, but fail in
certain important respects--an 80286 CPU does not make a machine
compatible. The BIOS code must also be compatible.
Because the 80286 does not have a direct way to switch from protected
mode to real mode, CA-Clipper/ExoSpace forces the switch by requesting a
reset (much like power on or rebooting). When it receives the reset,
your ROM BIOS startup code must be able to distinguish a restart from a
power up, in order to return to the CA-Clipper/ExoSpace kernel.
The 80386 and 80486 processors have a direct way to switch from
protected mode to real mode. If you have an 80386 or 80486, you will
not encounter this problem.
CA-Clipper/ExoSpace will run on any PC that:
1. Has an 80286, 80386, or 80486 CPU.
2. Can run MS-DOS or compatible operating system, Version 3.0 or later.
3. Supports IBM-PC/AT BIOS Interrupt 15h function 88h (get extended
memory size).
4. Is compatible with the IBM PC/AT in these respects:
. CMOS RAM (for saving time/date, configuration data, and the
restart code) accessible via I/O ports 70h and 71h
. Intel 8259-compatible Programmable Interrupt Controller,
accessible via I/O ports 20h and 21h (additional controllers may
be cascaded to the first)
. Intel 8042 auxiliary processor, with control port at I/O
60h, and status port at I/O address 64h
. "AT-compatible" ROM BIOS code that supports some form of
restarting
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