Hi

I've been looking at the mapping register:

port 0 "extended memory"
bits D0 - D3 switch pages by 32Kb
page 0 - ROM
digits D4 - D7 are not used

# 0000 - # 3FFF - first 16Kb of ROM
# 4000 - # 7FFF - first 16Kb of the first page of RAM
# 8000 - #FFFF - turnable pages of 32Kb
page 0 - ROM,
page 1 - first page of RAM
page 2 ... RAM


So, when register is 0, ROM is mapped on 8000H-FFFH
When register is 1, first 32 KB of RAM (ram 0) are mapped on 8000H-FFFH
When register is 2, second 32 KB of RAM (ram 1) are mapped on 8000H-FFFH
If you have a General Sound 512KB, the mapping register will be maximum value 15, so, when you are paging RAM 15-1=14, that means you can have different 15 pages mapped, so 15 X 16 = 480 KB

So the last 32 kb can't be used... right?

Using the same example, a General Sound with 128kb ram, can map up to 128-32=96 KB ram (but I read on some places than can map up to 112 KB)

Is there anything wrong here? Have I understood it well?

Thanks

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Could it be that:

# 4000 - # 7FFF - LAST 16 kb of RAM

?