Physical Memory: Up to 5MB total can be installed using the
expansion card. The card can hold 1, 2, 3, or 4MB. (Apple
specifications allow up to 8MB, but 4MB is largest that was
ever manufactured.) The original Portable uses static RAM,
and the later, Backlit Portable uses Pseudo–Static RAM.
The two types are not interchangeable, nor can they be
used on any other Macintosh. Portable and PowerBook
RAM are not interchangeable.
Extended Memory: The 68000 CPU in the Mac Portable
has no Memory Management Unit (which is required to run
virtual memory). There is currently no upgrade path to
provide an MMU to the Portable and there will probably
never be one.
PowerBook 100 
Physical Memory: Up to 8MB can be installed using the
expansion card. The card can hold 2MB, 4MB, or 6MB. The
6MB cards are available only from third parties (not Apple).
PowerBooks use Pseudo–Static Thin Small–Outline
Packages (or TSOPs). You must buy memory customized
for a PowerBook 100. Some third parties offer special
DRAM that works similarly to the TSOP. No extra software is
required to address the full 8MB.
Extended Memory: The 68000 CPU in the PowerBook 100
has no Memory Management Unit which is required to run
virtual memory. There is currently no upgrade path to
provide an MMU to the PB100 and there will probably never
be one.
PowerBook 140, 145 and 145B 
140, 145 has 2MB soldered on, 145B has 4MB soldered on.
Physical Memory: Up to 8MB can be installed using the
expansion card. The card can hold 2MB, 4MB, or 6MB. The
6MB cards are available only from third parties (not Apple).
PowerBooks use Pseudo–Static Thin Small–Outline
Packages (or TSOPs). You must buy memory customized
for a PowerBook 140/145/170. Some third parties offer
special DRAM that works similarly to the TSOP. No extra
software is required to address the full 8MB. 32–bit
addressing is available, but since only 8MB can be installed
it is not very useful. In most cases, it should be left Off. The
exception to this is when using extended memory on an
8MB machine - 32-bit addressing is needed to address
more than 14MB.
Extended Memory: The 68030 CPU in the PowerBook 140/145/145B has a built–in Memory Management Unit. Therefore, the PB140/145/145B can run RAM Doubler or virtual memory without additional hardware. However, use of virtual memory while on battery power is not recommended because it requires the hard drive to constantly spin, significantly reducing battery life. We recommend RAM Doubler.
PowerBook 150 
Physical Memory: Memory cards of up to 36MB can be
installed, for a total of 40MB. RAM is unique low–power,
self–refreshing dynamic RAM, and must run 80ns or faster.
Extended Memory: The 68030 CPU in the PowerBook 150
has a built–in Memory Management Unit. Therefore, the
PB150 can run RAM Doubler or virtual memory without
additional hardware. However, use of virtual memory while
on battery power is not recommended because it requires
the hard drive to constantly spin, significantly reducing
battery life. We recommend RAM Doubler.
PowerBook 160/165 
Physical Memory: 8MB can be installed using Apple’s 4MB
expansion kit, or up to 14MB can be installed using
You must buy 85ns or faster RAM for a PowerBook 180C.
Some third parties offer special DRAM that works similarly
to the TSOP.
Virtual Memory: The 68030 CPU in the PowerBook
180/180C has a built–in Memory Management Unit.
Therefore, the PB 180/180C can run RAM Doubler or virtual
memory without additional hardware. However, use of
virtual memory while on battery power is not recommended
because it requires the hard drive to constantly spin,
significantly reducing battery life. We recommend RAM
Doubler.
PowerBook 520 and 520c 
Standard Memory: Up to 36 MB may be installed using an
expansion card. You must buy 70ns or faster RAM for a
PowerBook 520 or 520c..
Virtual Memory: The 68040 CPU in the PowerBook
520/520c has a built–in Memory Management Unit.
Therefore, the PB 520/520c can run RAM Doubler or virtual
memory without additional hardware. However, use of
virtual memory while on battery power is not recommended
because it requires the hard drive to constantly spin,
significantly reducing battery life. We recommend RAM
Doubler.
PowerBook 540 and 540c 
Standard Memory: Up to 36 MB may be installed using an
expansion card. You must buy 70ns or faster RAM for a
PowerBook 540 or 540c..
Virtual Memory: The 68040 CPU in the PowerBook
540/540c has a built–in Memory Management Unit.
Therefore, the PB 540/540c can run RAM Doubler or virtual
memory without additional hardware. However, use of
virtual memory while on battery power is not recommended
because it requires the hard drive to constantly spin,
significantly reducing battery life. We recommend RAM
Doubler.
PowerBook Duo 210 
Physical Memory: Up to 12MB can be installed using
Apple’s 4MB or 8MB PowerBook Duo expansion kit, or up
to 24MB can be installed using third–party expansion cards.
RAM is unique for the PowerBook Duo (called low–power,
self–refreshing dynamic RAM), and must run 80ns or faster.
Extended Memory: The 68030 CPU in the Duo 210 has a
built–in Memory Management Unit. Therefore, the PBD 210
can run RAM Doubler or virtual memory without requiring
any additional hardware. However, use of virtual memory
while on battery power is not recommended because it
requires the hard drive to constantly spin, significantly
reducing battery life. We recommend RAM Doubler.
PowerBook Duo 230 
Physical Memory: Up to 12MB can be installed using
Apple’s 4MB or 8MB PowerBook Duo expansion kit, or up
to 24MB can be installed using third–party expansion cards.
RAM is unique for the PowerBook Duo (called low–power,
self–refreshing dynamic RAM), and must run 80ns or faster.
Extended Memory: The 68030 CPU in the Duo 230 has a
built–in Memory Management Unit. Therefore, the PBD 230
can run RAM Doubler or virtual memory without additional
hardware. However, use of virtual memory while on battery
power is not recommended because it requires the hard
drive to constantly spin, significantly reducing battery life.
We recommend RAM Doubler.
PowerBook Duo 250 
Physical Memory: Up to 12MB can be installed using
Apple’s 4MB or 8MB PowerBook Duo expansion kit, or up
to 24MB can be installed using third–party expansion cards.
RAM is unique for the PowerBook Duo (called low–power,
self–refreshing dynamic RAM), and must run 70ns or faster.
Extended Memory: The 68030 CPU in the Duo 250 has a
built–in Memory Management Unit. Therefore, the PBD 250
can run RAM Doubler or virtual memory without additional
hardware. However, use of virtual memory while on battery
power is not recommended because it requires the hard
drive to constantly spin, significantly reducing battery life.
We recommend RAM Doubler.
PowerBook Duo 270c 
Physical Memory: Up to 12MB can be installed using
Apple’s 4MB or 8MB PowerBook Duo expansion kit, or up
to 32MB can be installed using third–party expansion cards.
RAM is unique for the PowerBook Duo (called low–power,
self–refreshing dynamic RAM), and must run 70ns or faster.
Extended Memory: The 68030 CPU in the Duo 270c has a
built–in Memory Management Unit. Therefore, the PBD
270c can run RAM Doubler or virtual memory without
additional hardware. However, use of virtual memory while
on battery power is not recommended because it requires
the hard drive to constantly spin, significantly reducing
battery life. We recommend RAM Doubler.
PowerBook Duo 280 and 280c 
Physical Memory: Up to 12MB can be installed using
Apple’s 4MB or 8MB PowerBook Duo expansion kit, or up
to 40MB can be installed using third–party expansion cards.
RAM is unique for the PowerBook Duo (called low–power,
self–refreshing dynamic RAM), and must run 70ns or faster.
Extended Memory: The 68040 CPU in the Duo 280 has a
built–in Memory Management Unit. Therefore, the PBD
280 can run RAM Doubler or virtual memory without
additional hardware. However, use of virtual memory while
on battery power is not recommended because it requires
the hard drive to constantly spin, significantly reducing
battery life. We recommend RAM Doubler.
Macintosh Duo Dock and Duo Dock II
Video RAM: The Macintosh Duo Dock has 512K of 68–pin VRAM soldered on and 1 expansion slot in 1 bank. The standard 512K of VRAM is enough to support 8–bit color on all monitors up to and including the 16" color monitor. This can be expanded up to 1MB, which is enough to support 16–bit color on all monitors up to and including the 16" color monitor. The Duo Dock only supports 100ns 512K VRAM SIMMs.
Macintosh Duo MiniDock
Video RAM: The Macintosh Duo MiniDock has 512K of 68–pin VRAM soldered on. This is enough to support 8–bit color on all monitors up to and including the 16" color monitor. 512K is the maximum amount of VRAM that can be installed in the Duo MiniDock.