Shark memory map?

I've got a shark.  It works fine.

But I've got only one, so I'd like to insulate myself against it
breaking.

So, I figured, I'd build an emulator while it still works and I thus
have something to compare against.  But that means I need more detailed
info.

I've got EC-R8JLB-TE, the user guide.  It helps some.  I probably can
figure out a lot by experimenting; I did find a note in the user guide
(page 4-12) which implies that the ROM exists based at 0x8a000000 but
there is a PAL in the address path which effectively ORs 0x8a000000
into the address lines for the sake of early startup, so that would be
an interesting place to start looking.

But I thought I'd ask here first to see if anyone can point me at a
document already written that describes the memory map and such.
Presumably something of the sort existed once upon a time - DEC could
hardly have built it without one - but that's not to say that any
copies made it out to the public, nor for that matter than any copies
still exist.

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