<s>
The	O
Macintosh	B-Device
512K	I-Device
is	O
a	O
personal	B-Device
computer	I-Device
that	O
was	O
designed	O
,	O
manufactured	O
and	O
sold	O
by	O
Apple	O
Computer	O
from	O
September	O
1984	O
to	O
April	O
1986	O
.	O
</s>
<s>
It	O
is	O
the	O
first	O
update	O
to	O
the	O
original	B-Device
Macintosh	I-Device
128K	I-Device
.	O
</s>
<s>
It	O
was	O
virtually	O
identical	O
to	O
the	O
previous	O
Macintosh	B-Device
,	O
differing	O
primarily	O
in	O
the	O
amount	O
of	O
built-in	O
random-access	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
The	O
increased	O
memory	O
turned	O
the	O
Macintosh	B-Device
into	O
a	O
more	O
business-capable	O
computer	O
and	O
gained	O
the	O
ability	O
to	O
run	O
more	O
software	O
.	O
</s>
<s>
It	O
is	O
the	O
earliest	O
Macintosh	B-Device
model	O
that	O
can	O
be	O
used	O
as	O
an	O
AppleShare	B-General_Concept
server	O
and	O
,	O
with	O
a	O
bridge	O
Mac	O
,	O
communicate	O
with	O
modern	O
devices	O
.	O
</s>
<s>
The	O
Mac	B-Device
512K	I-Device
originally	O
shipped	O
with	O
Macintosh	B-Application
System	I-Application
1.1	B-Application
but	O
was	O
able	O
to	O
run	O
all	O
versions	O
of	O
Mac	B-Application
OS	I-Application
up	O
to	O
System	O
4.1	B-Application
.	O
</s>
<s>
It	O
was	O
replaced	O
by	O
the	O
Macintosh	B-Device
512Ke	I-Device
and	O
the	O
Macintosh	B-Device
Plus	I-Device
.	O
</s>
<s>
All	O
support	O
for	O
the	O
Mac	B-Device
512K	I-Device
was	O
discontinued	O
on	O
September	O
1	O
,	O
1998	O
.	O
</s>
<s>
Like	O
the	O
Macintosh	B-Device
128K	I-Device
before	O
it	O
,	O
the	O
512K	O
contained	O
a	O
Motorola	B-Device
68000	I-Device
connected	O
to	O
512KB	O
of	O
DRAM	O
by	O
a	O
16-bit	B-Device
data	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
The	O
large	O
increase	O
earned	O
it	O
the	O
nickname	O
Fat	B-Device
Mac	I-Device
.	O
</s>
<s>
A	O
64KB	O
ROM	B-Device
chip	I-Device
boosts	O
the	O
effective	O
memory	O
to	O
576KB	O
,	O
but	O
this	O
is	O
offset	O
by	O
the	O
display	O
's	O
22KB	O
framebuffer	B-Algorithm
,	O
which	O
is	O
shared	O
with	O
the	O
DMA	B-General_Concept
video	O
controller	O
.	O
</s>
<s>
It	O
shared	O
a	O
revised	O
logic	O
board	O
with	O
the	O
rebadged	O
Macintosh	B-Device
128K	I-Device
(	O
previously	O
just	O
called	O
the	O
Macintosh	B-Device
)	O
,	O
which	O
streamlined	O
manufacturing	O
.	O
</s>
<s>
Apple	O
sold	O
a	O
memory	O
upgrade	O
for	O
the	O
Macintosh	B-Device
128K	I-Device
for	O
$995	O
initially	O
,	O
and	O
reduced	O
the	O
price	O
when	O
256	O
kb	O
DRAM	O
prices	O
fell	O
months	O
later	O
.	O
</s>
<s>
The	O
applications	O
MacPaint	B-Operating_System
and	O
MacWrite	B-Operating_System
were	O
still	O
bundled	O
with	O
the	O
Mac	O
.	O
</s>
<s>
Soon	O
after	O
this	O
model	O
was	O
released	O
,	O
several	O
other	O
applications	O
became	O
available	O
,	O
including	O
MacDraw	B-Operating_System
,	O
MacProject	B-Operating_System
,	O
Macintosh	B-Device
Pascal	B-Application
and	O
others	O
.	O
</s>
<s>
In	O
particular	O
,	O
Microsoft	B-Application
Excel	I-Application
,	O
which	O
was	O
written	O
specifically	O
for	O
the	O
Macintosh	B-Device
,	O
required	O
a	O
minimum	O
of	O
512KB	O
of	O
RAM	B-Architecture
,	O
but	O
solidified	O
the	O
Macintosh	B-Device
as	O
a	O
serious	O
business	O
computer	O
.	O
</s>
<s>
Models	O
with	O
the	O
enhanced	O
ROM	B-Device
also	O
supported	O
Apple	O
's	O
Switcher	O
,	O
allowing	O
cooperative	O
multitasking	O
among	O
(	O
necessarily	O
few	O
)	O
applications	O
.	O
</s>
<s>
It	O
utilized	O
Apple	O
's	O
built-in	O
networking	O
scheme	O
LocalTalk	B-Device
which	O
allows	O
sharing	O
of	O
devices	O
among	O
several	O
users	O
.	O
</s>
<s>
The	O
512K	O
was	O
the	O
oldest	O
Macintosh	B-Device
capable	O
of	O
supporting	O
Apple	O
's	O
AppleShare	B-General_Concept
built-in	O
file	O
sharing	O
network	O
,	O
when	O
introduced	O
in	O
1987	O
.	O
</s>
<s>
The	O
original	O
512K	O
could	O
accept	O
Macintosh	B-Application
system	I-Application
software	I-Application
up	O
to	O
version	O
4.1	B-Application
;	O
System	B-Application
Software	I-Application
5	O
was	O
possible	O
if	O
used	O
with	O
the	O
Hard	B-Device
Disk	I-Device
20	I-Device
.	O
</s>
<s>
An	O
updated	O
version	O
replaced	O
the	O
Macintosh	B-Device
512K	I-Device
and	O
debuted	O
as	O
the	O
Macintosh	B-Device
512K	I-Device
enhanced	O
in	O
April	O
1986	O
.	O
</s>
<s>
It	O
differed	O
from	O
the	O
original	O
512K	O
in	O
that	O
it	O
had	O
an	O
800	B-Device
KB	I-Device
floppy	I-Device
disk	I-Device
drive	I-Device
and	O
the	O
same	O
improved	O
ROM	B-Device
as	O
the	O
Macintosh	B-Device
Plus	I-Device
.	O
</s>
<s>
The	O
stock	O
512K	O
could	O
also	O
use	O
an	O
800KB	O
floppy	O
disk	O
drive	O
as	O
well	O
as	O
the	O
Hard	B-Device
Disk	I-Device
20	I-Device
,	O
the	O
first	O
hard	O
disk	O
manufactured	O
by	O
Apple	O
exclusively	O
for	O
use	O
with	O
the	O
512K	O
,	O
but	O
required	O
a	O
special	O
system	O
file	O
(	O
not	O
required	O
by	O
the	O
512Ke	O
)	O
that	O
loaded	O
the	O
improved	O
ROM	B-Device
code	O
into	O
RAM	B-Architecture
,	O
thus	O
reducing	O
the	O
RAM	B-Architecture
available	O
for	O
other	O
uses	O
.	O
</s>
<s>
One	O
further	O
OEM	O
upgrade	O
replaced	O
the	O
logic	O
board	O
and	O
the	O
rear	O
case	O
entirely	O
with	O
that	O
of	O
the	O
Macintosh	B-Device
Plus	I-Device
.	O
</s>
<s>
As	O
with	O
the	O
original	O
Macintosh	B-Device
,	O
the	O
512K	O
was	O
designed	O
with	O
no	O
slots	O
for	O
upgrade	O
boards	O
and	O
had	O
no	O
hard-disk	O
controller	O
,	O
so	O
the	O
few	O
internal	O
upgrades	O
that	O
were	O
available	O
for	O
the	O
512K	O
,	O
such	O
as	O
General	O
Computer	O
's	O
US$	O
2,795	O
Hyperdrive	O
hard	O
drive	O
,	O
had	O
to	O
plug	O
directly	O
into	O
the	O
68000	B-Device
processor	O
socket	O
.	O
</s>
<s>
Other	O
such	O
upgrades	O
included	O
"	O
snap-on	O
"	O
SCSI	B-Architecture
cards	O
and	O
RAM	B-Architecture
upgrades	O
of	O
2MB	O
or	O
more	O
.	O
</s>
