<s>
The	O
Mega	B-Device
II	I-Device
is	O
a	O
custom	O
chip	O
from	O
Apple	O
Computer	O
that	O
is	O
essentially	O
an	O
entire	O
Apple	B-Device
II	I-Device
computer-on-a-chip	B-Architecture
.	O
</s>
<s>
It	O
was	O
most	O
predominantly	O
used	O
in	O
the	O
Apple	B-Device
IIGS	I-Device
microcomputer	B-Architecture
,	O
and	O
the	O
basis	O
for	O
a	O
modified	O
variant	O
,	O
called	O
the	O
"	O
Gemini	O
"	O
chip	O
,	O
which	O
was	O
later	O
used	O
in	O
the	O
Apple	B-Device
IIe	I-Device
Card	I-Device
for	O
the	O
Macintosh	B-Device
LC	I-Device
.	O
</s>
<s>
This	O
custom	O
application-specific	O
integrated	O
circuit	O
(	O
ASIC	O
)	O
integrated	O
most	O
of	O
the	O
circuitry	O
from	O
earlier	O
Apple	B-Device
II	I-Device
models	O
onto	O
one	O
84-pin	O
PLCC	B-Algorithm
integrated	O
circuit	O
,	O
drastically	O
simplifying	O
design	O
and	O
cost	O
for	O
Apple	O
.	O
</s>
<s>
The	O
Mega	B-Device
II	I-Device
contained	O
the	O
functional	O
equivalent	O
of	O
an	O
entire	O
Apple	O
IIe	O
computer	O
(	O
sans	O
processor	O
)	O
,	O
which	O
,	O
combined	O
with	O
the	O
65C02	B-General_Concept
emulation	O
mode	O
of	O
the	O
65C816	B-General_Concept
processor	O
,	O
plus	O
ROM	B-Device
and	O
RAM	O
,	O
provided	O
full	O
support	O
for	O
legacy	O
(	O
8-bit	O
)	O
Apple	B-Device
II	I-Device
software	O
in	O
the	O
Apple	B-Device
IIGS	I-Device
.	O
</s>
<s>
The	O
Mega	B-Device
II	I-Device
has	O
the	O
built-in	O
equivalent	O
of	O
the	O
IOU	O
and	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
(	O
MMU	O
)	O
chips	O
,	O
video	O
and	O
keyboard	O
ROMs	O
(	O
with	O
support	O
for	O
other	O
display	O
languages	O
)	O
and	O
likely	O
the	O
keyboard	O
encoder	O
found	O
in	O
the	O
IIe	O
.	O
</s>
<s>
It	O
also	O
has	O
a	O
built-in	O
keyboard	O
and	O
mouse	O
controller	O
(	O
neither	O
were	O
used	O
in	O
the	O
Apple	B-Device
IIGS	I-Device
)	O
.	O
</s>
<s>
Potentially	O
the	O
Mega	B-Device
II	I-Device
could	O
have	O
been	O
used	O
to	O
produce	O
future	O
models	O
of	O
the	O
8-bit	O
Apple	B-Device
II	I-Device
with	O
a	O
very	O
low	O
chip	O
count	O
(	O
and	O
reduced	O
physical	O
size	O
)	O
but	O
instead	O
used	O
for	O
IIe	O
emulation	O
on	O
the	O
Apple	B-Device
IIGS	I-Device
and	O
Macintosh	B-Device
LC	I-Device
with	O
plug-in	O
card	O
,	O
which	O
used	O
a	O
similar	O
all-in-one	O
IC	O
based	O
on	O
it	O
.	O
</s>
<s>
It	O
was	O
also	O
used	O
as	O
support	O
circuitry	O
on	O
the	O
Apple	B-Device
II	I-Device
Video	O
Overlay	O
Card	O
.	O
</s>
<s>
In	O
1984	O
,	O
after	O
the	O
cancellation	O
of	O
the	O
Apple	B-Device
IIx	I-Device
project	O
,	O
Dan	O
Hillman	O
and	O
Jay	O
Rickard	O
,	O
engineers	O
at	O
Apple	O
,	O
were	O
assigned	O
to	O
lower	O
the	O
cost	O
of	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
They	O
were	O
able	O
to	O
compress	O
the	O
design	O
of	O
almost	O
the	O
entire	O
Apple	B-Device
II	I-Device
onto	O
one	O
chip	O
which	O
they	O
named	O
Mega	B-Device
II	I-Device
.	O
</s>
<s>
When	O
the	O
16-bit	B-Device
Apple	B-Device
IIGS	I-Device
project	O
came	O
onto	O
the	O
table	O
,	O
the	O
virtually	O
completed	O
design	O
of	O
the	O
Mega	B-Device
II	I-Device
was	O
a	O
clear	O
starting	O
point	O
for	O
seamless	O
backwards	O
8-bit	O
system	O
compatibility	O
.	O
</s>
