May 2014
Intermediate to advanced
320 pages
13h 41m
English
Content preview from Servicing Personal Computers, 3rd Edition
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Servicing 68000-based microcomputers 273
Address (Hex)
coooo
40000
28000
20000
18000
ocooo
00000
Expansion I/O
Expansion RAM
System RAM
Screen RAM
I/O
Plug-in ROM
System ROM
Figure
7.1.
Sinclair QL memory map
plug-in expansion ROM. The screen RAM occupies 32K bytes of memory from 20000 to
27FFF hex. whilst the remaining 96K bytes of internally fitted system board RAM extends from
28000 to 3FFFF hex. Expansion RAM (in the form of plug-in cards from third-party
manufacturers and vendors) can extend the RAM above 40000 hex. Finally, the region above
COOOO is reserved for expansion I/O.
QL firmware
The software contained within the two QL syste ...