<s>
The	O
Macintosh	B-Device
IIsi	I-Device
is	O
a	O
personal	B-Device
computer	I-Device
designed	O
,	O
manufactured	O
and	O
sold	O
by	O
Apple	O
Computer	O
,	O
Inc	O
.	O
from	O
October	O
1990	O
to	O
March	O
1993	O
.	O
</s>
<s>
Introduced	O
as	O
a	O
lower-cost	O
alternative	O
to	O
the	O
other	O
Macintosh	B-Device
II	I-Device
family	I-Device
of	O
desktop	O
models	O
,	O
it	O
was	O
popular	O
for	O
home	O
use	O
,	O
as	O
it	O
offered	O
more	O
expandability	O
and	O
performance	O
than	O
the	O
Macintosh	B-Device
LC	I-Device
,	O
which	O
was	O
introduced	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
IIsi	B-Device
remained	O
on	O
the	O
market	O
for	O
two	O
and	O
a	O
half	O
years	O
and	O
was	O
discontinued	O
shortly	O
after	O
the	O
introduction	O
of	O
its	O
replacement	O
,	O
the	O
Centris	B-Device
610	I-Device
.	O
</s>
<s>
The	O
IIsi	B-Device
's	O
case	O
design	O
is	O
a	O
compact	O
desktop	O
unit	O
not	O
used	O
for	O
any	O
other	O
Macintosh	O
model	O
,	O
one	O
of	O
the	O
few	O
Macintosh	O
designs	O
that	O
was	O
used	O
for	O
a	O
single	O
model	O
.	O
</s>
<s>
Positioned	O
below	O
the	O
Macintosh	B-Device
IIci	I-Device
as	O
Apple	O
's	O
entry-level	O
professional	O
model	O
,	O
the	O
IIsi	B-Device
's	O
price	O
was	O
lowered	O
by	O
the	O
redesign	O
of	O
the	O
motherboard	O
substituting	O
a	O
different	O
memory	O
controller	O
and	O
the	O
deletion	O
of	O
all	O
but	O
one	O
of	O
the	O
expansion	O
card	O
slots	O
(	O
a	O
single	O
Processor	B-Device
Direct	I-Device
Slot	I-Device
)	O
and	O
removal	O
of	O
the	O
level	O
2	O
cache	O
slot	O
.	O
</s>
<s>
The	O
Motorola	B-General_Concept
68882	I-General_Concept
FPU	B-General_Concept
was	O
an	O
optional	O
upgrade	O
,	O
mounted	O
on	O
a	O
special	O
plug-in	O
card	O
.	O
</s>
<s>
Ports	O
included	O
SCSI	B-Architecture
,	O
two	O
serial	O
ports	O
,	O
an	O
ADB	B-Device
port	I-Device
,	O
a	O
floppy	O
drive	O
port	O
,	O
and	O
3.5mm	O
stereo	O
headphone	O
sound	O
output	O
and	O
microphone	O
sound	O
input	O
sockets	O
.	O
</s>
<s>
A	O
bridge	O
card	O
was	O
available	O
for	O
the	O
IIsi	B-Device
to	O
convert	O
the	O
Processor	B-Device
Direct	I-Device
slot	I-Device
to	O
a	O
standard	O
internal	O
NuBus	B-Device
card	O
slot	O
,	O
compatible	O
with	O
other	O
machines	O
in	O
the	O
Macintosh	B-Device
II	I-Device
family	I-Device
.	O
</s>
<s>
The	O
bridge	O
card	O
included	O
the	O
68882	B-General_Concept
FPU	B-General_Concept
to	O
improve	O
floating-point	O
performance	O
.	O
</s>
<s>
The	O
NuBus	B-Device
card	O
was	O
mounted	O
horizontally	O
above	O
the	O
motherboard	O
.	O
</s>
<s>
To	O
cut	O
costs	O
,	O
the	O
IIsi	B-Device
's	O
video	O
shared	O
the	O
main	O
system	O
memory	O
,	O
which	O
also	O
had	O
the	O
effect	O
of	O
slowing	O
down	O
video	O
considerably	O
,	O
especially	O
as	O
the	O
IIsi	B-Device
had	O
1MB	O
of	O
slow	O
RAM	O
soldered	O
to	O
the	O
motherboard	O
.	O
</s>
<s>
David	O
Pogue	O
's	O
book	O
Macworld	O
Macintosh	O
Secrets	O
observed	O
that	O
one	O
could	O
speed	O
up	O
video	O
considerably	O
if	O
one	O
set	O
the	O
disk	O
cache	O
size	O
large	O
enough	O
to	O
force	O
the	O
computer	O
to	O
draw	O
video	O
RAM	O
from	O
faster	O
RAM	O
installed	O
in	O
the	O
SIMM	B-General_Concept
banks	O
.	O
</s>
<s>
The	O
IIsi	B-Device
also	O
suffers	O
from	O
sound	O
difficulties	O
:	O
over	O
time	O
,	O
the	O
speaker	O
contacts	O
can	O
fail	O
,	O
causing	O
the	O
sound	O
to	O
periodically	O
drop	O
out	O
.	O
</s>
<s>
As	O
the	O
IIsi	B-Device
is	O
the	O
only	O
Macintosh	O
to	O
use	O
this	O
case	O
design	O
,	O
these	O
issues	O
were	O
never	O
corrected	O
in	O
a	O
subsequent	O
model	O
.	O
</s>
<s>
The	O
IIsi	B-Device
was	O
designed	O
to	O
be	O
easily	O
and	O
cheaply	O
manufactured	O
,	O
such	O
that	O
no	O
tools	O
were	O
required	O
to	O
put	O
one	O
together	O
–	O
everything	O
is	O
held	O
in	O
place	O
with	O
clips	O
or	O
latches	O
.	O
</s>
<s>
Because	O
of	O
its	O
heritage	O
as	O
a	O
cut-down	O
IIci	B-Device
,	O
it	O
was	O
a	O
simple	O
modification	O
to	O
substitute	O
a	O
new	O
clock	O
crystal	O
to	O
increase	O
the	O
system	O
's	O
clock	O
rate	O
to	O
25MHz	O
for	O
a	O
slight	O
increase	O
in	O
performance	O
and	O
a	O
large	O
increase	O
in	O
video	O
rendering	O
speed	O
.	O
</s>
<s>
Charles	O
Bukowski	O
was	O
an	O
enthusiastic	O
user	O
of	O
the	O
IIsi	B-Device
.	O
</s>
