> segment (8K segments).  On the 386 the base address of each of the
 > segments is a 32 bit number, so 8K segments of size 64K gives 512 meg
 > of addressable memory.

Only 4K entries in each descriptor table is possible. See below.

 >    Each task has a LDT (local descriptor table) that is the same size
 > as the GDT, so in theory a 286 protected mode task running on a 386
 > could access 1gig.  Perhaps David Nugent will be able to explain
 > what's wrong with my theory.

There are only 8K unique descriptors available to any task in total. Each
desciptor is 16 bits (obviously), less 2 for priviledge level, less 1 for
the LDT/GDT select bit, leaving only 13 bits remaining for the actual
descriptor table index.

2^13 = 8192.


david

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