Rom wait states, Rom 1, Ram 1 – Apple Macintosh PowerBook 165c User Manual
Page 18: Rom wait states 1
C H A P T E R 1
Hardware
8
Hardware Overview
Figure 1-3
32-bit and 24-bit memory map comparison
ROM
1
The Macintosh PowerBook 165c ROM is identical to the ROM used in the PowerBook 160
and PowerBook 180 computers. The ROM chips have been moved from the secondary
logic board to a new RAM/ROM board to make room for the color display circuits.
A new 32K x 8-bit declaration ROM appears in NuBus
™
slot $C address space and
provides firmware support for the color LCD.
ROM Wait States
1
ROM accesses by the CPU require 4 processor wait states (7 clock cycles at 33 MHz),
which is equivalent to 180 ns per access.
RAM
1
The PowerBook 165c includes 4 MB of 85 ns pseudostatic RAM, consisting of eight
512K x 8-bit chips. The RAM chips are contained on a new RAM/ROM board to provide
room for the color display circuitry on the secondary logic board.
$FF FFFF
I/O space
Slot E (external video)
ROM
RAM
8 MB maximum,
one continuous bank
$F0 0000
$E0 0000
$90 0000
$80 0000
$00 0000
32-bit memory map
24-bit memory map
$6000 0000
$5000 0000
$4400 0000
$4000 0000
$0400 0000
$00E0 0000
$0000 0000
$FFFF FFFF
$FEF0 FFFF
I/O
Reserved
ROM
Expansion RAM
(bus error)
Illegal
RAM
14 MB maximum,
one continuous bank
Reserved
Slot E (external video)
Reserved
$FE00 0000
$FD00 0000
$FC00 0000
Reserved
Slot C (internal video)
Reserved
$D0 0000
$C0 0000
Reserved
Slot C (internal video)