DESCRIPTION

This directory holds Xinu sources for Virtual Box.  They are derived from
the Galileo version described in:

	Douglas Comer, Operating System Design -- The Xinu Approach,
	Second edition, CRC Press, 2015.

The changes are:

 1) The tty driver uses port-mapped I/O in place of the memory-mapped I/O
    used on the Galileo.  The include file io.h contains macros that
    handle both.  Also, in uart.h, the Control and Status Registers are
    sing;e bytes instead of the word-oriented approach used on the Galileo.

 2) The Ethernet driver is for an Intel 82545EM chip, which is a form of
    Intel's E1000E Ethernet design.  The internals of the driver differ
    completely from the driver used with the Ethernet on the Galileo SoC.

 3) The startup sequence (file start.S) differs from the Galileo startup
    sequence.  It may be possible to move toward a more common form; we
    adopted an older startup sequence that works, and haven't tried to
    blend them.

 4) The platform initialization used with the Galileo (platinit.c) has
    been removed, and basic PC functions have been substituted (in file
    i386.c).

 5) The Galileo version uses the memory map left by grub to construct a
    free list.  We deleted the code that depends on grub and substituted
    simpler free list code from an earlier version of Xinu because we
    had trouble reading the grub free list.  Additional work may be
    needed to ensure the free list is correct.

 6) The code includes a pipe device, and the shell has pipes.