[Open-graphics] Address space of S3

[Timothy Normand Miller]

The "engine" space is broken up into 64 1K-word (word=32-bit)
sections.  Other logic can subdivide it further as necessary, but
that's how it's decoded in the "address_decode" block in the S3.
Patrick had cleverly minimized the logic for the blocks that are in
there, but I think I want to go ahead and generalize it, so the
address decoder will basically be a 6-to-64 demux.  For the moment,
I'm going to just hack it to use the new addresses; later, we can
rewrite it.  The word address is 16 bits, meaning that there are 64K
words or 256K bytes of "engine" address space.


Word address:  0x0000 - 0x03ff
PCI address: 0x0000 - 0x0ffc
# Reserved for XP10 config registers

Word address:  0x0400 - 0x07ff
PCI address: 0x1000 - 0x1ffc
# Memory controller/arbiter

Word address: 0x0800 - 0x0bff
PCI address: 0x2000 - 0x2ffc
# Unused

Word address: 0x1000 - 0x13ff
PCI address: 0x3000 - 0x3ffc
# Video controller 0

Word address: 0x1400 - 0x17ff
PCI address: 0x4000 - 0x4ffc
# Video controller 1


In the next email, I'll break down the memory controller and arbiter registers.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project