<s>
The	O
Amiga	B-Device
500	I-Device
,	O
also	O
known	O
as	O
the	O
A500	O
,	O
is	O
the	O
first	O
low-end	O
version	O
of	O
the	O
Amiga	B-Device
home	O
computer	O
.	O
</s>
<s>
It	O
contains	O
the	O
same	O
Motorola	B-Device
68000	I-Device
as	O
the	O
Amiga	B-Device
1000	I-Device
,	O
as	O
well	O
as	O
the	O
same	O
graphics	O
and	O
sound	O
coprocessors	O
,	O
but	O
is	O
in	O
a	O
smaller	O
case	O
similar	O
to	O
that	O
of	O
the	O
Commodore	B-Device
128	I-Device
.	O
</s>
<s>
Commodore	O
announced	O
the	O
Amiga	B-Device
500	I-Device
at	O
the	O
January	O
1987	O
winter	O
Consumer	O
Electronics	O
Showat	O
the	O
same	O
time	O
as	O
the	O
high-end	O
Amiga	B-Device
2000	I-Device
.	O
</s>
<s>
It	O
competed	O
directly	O
against	O
models	O
in	O
the	O
Atari	B-Device
ST	I-Device
line	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
was	O
sold	O
in	O
the	O
same	O
retail	O
outlets	O
as	O
the	O
Commodore	O
64	O
,	O
as	O
opposed	O
to	O
the	O
computer	O
store-only	O
Amiga	B-Device
1000	I-Device
.	O
</s>
<s>
It	O
was	O
followed	O
by	O
a	O
revised	O
version	O
of	O
the	O
computer	O
,	O
the	O
Amiga	B-Device
500	I-Device
Plus	O
,	O
and	O
the	O
500	O
series	O
was	O
discontinued	O
in	O
1992	O
.	O
</s>
<s>
In	O
October	O
1989	O
,	O
the	O
Amiga	B-Device
500	I-Device
dropped	O
its	O
price	O
from	O
£499	O
to	O
£399	O
and	O
was	O
bundled	O
with	O
the	O
Batman	B-Application
Pack	O
in	O
the	O
United	O
Kingdom	O
(	O
from	O
October	O
1989	O
to	O
September	O
1990	O
)	O
which	O
included	O
the	O
games	O
Batman	B-Application
,	O
F/A	B-Application
-18	I-Application
Interceptor	I-Application
,	O
The	B-Application
New	I-Application
Zealand	I-Application
Story	I-Application
and	O
the	O
bitmap	O
graphics	O
editor	O
Deluxe	B-Application
Paint	I-Application
2	I-Application
.	O
</s>
<s>
Also	O
included	O
was	O
the	O
Amiga	B-Protocol
video	I-Protocol
connector	I-Protocol
which	O
allows	O
the	O
A500	O
to	O
be	O
used	O
with	O
a	O
conventional	O
CRT	O
television	O
.	O
</s>
<s>
In	O
November	O
1991	O
,	O
the	O
enhanced	O
Amiga	B-Device
500	I-Device
Plus	O
replaced	O
the	O
500	O
in	O
some	O
markets	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
Plus	O
was	O
virtually	O
identical	O
except	O
for	O
its	O
new	O
operating	O
system	O
,	O
and	O
in	O
mid-1992	O
,	O
the	O
two	O
were	O
discontinued	O
and	O
effectively	O
replaced	O
by	O
the	O
Amiga	B-Device
600	I-Device
.	O
</s>
<s>
In	O
late	O
1992	O
,	O
Commodore	O
released	O
the	O
Amiga	B-Application
1200	I-Application
,	O
a	O
machine	O
closer	O
in	O
concept	O
to	O
the	O
original	O
Amiga	B-Device
500	I-Device
,	O
but	O
with	O
significant	O
technical	O
improvements	O
.	O
</s>
<s>
Despite	O
this	O
,	O
neither	O
the	O
A1200	B-Application
nor	O
the	O
A600	O
replicated	O
the	O
commercial	O
success	O
of	O
its	O
predecessor	O
.	O
</s>
<s>
By	O
this	O
time	O
,	O
the	O
home	O
market	O
was	O
strongly	O
shifting	O
to	O
IBM	B-Device
PC	I-Device
compatibles	O
with	O
VGA	B-Protocol
graphics	I-Protocol
and	O
the	O
"	O
low-cost	O
"	O
Macintosh	B-Device
Classic	I-Device
,	O
LC	B-Device
,	O
and	O
IIsi	B-Device
models	O
.	O
</s>
<s>
Outwardly	O
resembling	O
the	O
Commodore	B-Device
128	I-Device
and	O
codenamed	O
"	O
Rock	O
Lobster	O
"	O
during	O
development	O
,	O
the	O
Amiga	B-Device
500	I-Device
's	O
base	O
houses	O
a	O
keyboard	O
and	O
a	O
CPU	B-General_Concept
in	O
one	O
shell	O
,	O
unlike	O
the	O
Amiga	B-Device
1000	I-Device
.	O
</s>
<s>
The	O
keyboard	O
for	O
Amiga	B-Device
500s	I-Device
sold	O
in	O
the	O
United	O
States	O
contains	O
94	O
keys	O
,	O
including	O
ten	O
function	B-Application
keys	I-Application
,	O
four	O
cursor	O
keys	O
,	O
and	O
a	O
number	O
pad	O
.	O
</s>
<s>
It	O
uses	O
a	O
Motorola	B-Device
68000	I-Device
microprocessor	I-Device
running	O
at	O
in	O
NTSC	O
regions	O
and	O
in	O
PAL	B-Language
regions	O
.	O
</s>
<s>
The	O
CPU	B-General_Concept
implements	O
a	O
32-bit	O
model	O
and	O
has	O
32-bit	O
registers	O
,	O
but	O
it	O
has	O
a	O
16-bit	O
main	O
ALU	B-General_Concept
and	O
uses	O
a	O
16-bit	O
external	O
data	O
bus	O
and	O
a	O
23-bit	O
address	O
bus	O
,	O
providing	O
a	O
maximum	O
of	O
16MB	O
of	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
Also	O
built	O
in	O
to	O
the	O
base	O
of	O
the	O
computer	O
is	O
a	O
-inch	O
floppy	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
The	O
user	O
can	O
also	O
install	O
up	O
to	O
three	O
external	O
floppy	B-Device
drives	I-Device
,	O
either	O
-	O
or	O
-inch	O
,	O
via	O
the	O
disk	O
drive	O
port	O
.	O
</s>
<s>
The	O
second	O
and	O
third	O
additional	O
drives	O
are	O
installed	O
by	O
daisy-chaining	B-Application
them	O
.	O
</s>
<s>
Supported	O
by	O
these	O
drives	O
are	O
double-sided	O
disks	O
with	O
a	O
capacity	O
of	O
901,120	O
bytes	O
,	O
as	O
well	O
as	O
360	O
-	O
and	O
720-KB	O
disks	O
formatted	O
for	O
IBM	B-Device
PC	I-Device
compatibles	O
.	O
</s>
<s>
The	O
earliest	O
Amiga	B-Device
500	I-Device
models	O
use	O
nearly	O
the	O
same	O
Original	B-Device
Amiga	I-Device
chipset	I-Device
as	O
the	O
Amiga	B-Device
1000	I-Device
.	O
</s>
<s>
Resolutions	O
vary	O
from	O
320×200	O
(	O
up	O
to	O
32	O
colors	O
)	O
to	O
640×400	O
(	O
up	O
to	O
16	O
colors	O
)	O
for	O
NTSC	O
(	O
704×484	O
overscan	O
)	O
and	O
320×256	O
to	O
640×512	O
for	O
PAL	B-Language
(	O
704×576	O
overscan	O
.	O
)	O
</s>
<s>
The	O
system	O
uses	O
planar	B-Device
graphics	O
,	O
with	O
up	O
to	O
five	O
bitplanes	O
(	O
four	O
in	O
high	O
resolution	O
)	O
allowing	O
2-	O
,	O
4-	O
,	O
8-	O
,	O
16-	O
,	O
and	O
32-color	O
screens	O
,	O
from	O
a	O
palette	O
of	O
4096	O
colors	O
.	O
</s>
<s>
Two	O
special	O
graphics	O
modes	O
are	O
also	O
available	O
:	O
Extra	O
HalfBrite	O
,	O
which	O
uses	O
a	O
6th	O
bitplane	O
as	O
a	O
mask	O
to	O
cut	O
the	O
brightness	O
of	O
any	O
pixel	B-Algorithm
in	O
half	O
(	O
resulting	O
in	O
32	O
arbitrary	O
colors	O
plus	O
32	O
more	O
colors	O
set	O
at	O
half	O
the	O
value	O
of	O
the	O
first	O
32	O
)	O
,	O
and	O
Hold-And-Modify	O
(	O
HAM	O
)	O
which	O
allows	O
all	O
4096	O
colors	O
to	O
be	O
used	O
on	O
screen	O
simultaneously	O
.	O
</s>
<s>
Later	O
revisions	O
of	O
the	O
chipset	O
are	O
PAL/NTSC	O
switchable	O
in	O
software	O
.	O
</s>
<s>
The	O
sound	O
chip	O
produces	O
four	O
hardware-mixed	O
channels	O
,	O
two	O
to	O
the	O
left	O
and	O
two	O
to	O
the	O
right	O
,	O
of	O
8-bit	O
PCM	B-Algorithm
at	O
a	O
sampling	O
frequency	O
up	O
to	O
.	O
</s>
<s>
With	O
DMA	B-General_Concept
disabled	O
it	O
's	O
possible	O
to	O
output	O
with	O
a	O
sampling	O
frequency	O
up	O
to	O
.	O
</s>
<s>
The	O
stock	O
system	O
comes	O
with	O
AmigaOS	B-Application
version	O
1.2	O
or	O
1.3	O
and	O
of	O
chip	B-Device
RAM	I-Device
(	O
150	O
ns	O
access	O
time	O
)	O
,	O
one	O
built-in	O
double-density	O
standard	B-Device
floppy	I-Device
disk	I-Device
drive	I-Device
that	O
is	O
completely	O
programmable	O
and	O
can	O
read	O
IBM	B-Device
PC	I-Device
disks	O
,	O
standard	O
Amiga	B-Device
disks	O
,	O
and	O
up	O
to	O
using	O
custom-formatting	O
drivers	O
.	O
</s>
<s>
Despite	O
the	O
lack	O
of	O
Amiga	B-Device
2000-compatible	I-Device
internal	I-Device
expansion	I-Device
slots	I-Device
,	O
there	O
are	O
many	O
ports	O
and	O
expansion	O
options	O
.	O
</s>
<s>
There	O
are	O
two	O
DE9M	B-Protocol
Atari	B-Protocol
joystick	I-Protocol
ports	I-Protocol
for	O
joysticks	B-Device
or	O
mice	B-Device
,	O
and	O
stereo	O
audio	O
RCA	B-Protocol
connectors	I-Protocol
(	O
1V	O
p-p	O
)	O
.	O
</s>
<s>
There	O
is	O
a	O
floppy	B-Device
drive	I-Device
port	O
for	O
daisy-chaining	B-Application
up	O
to	O
three	O
extra	O
floppy	B-Device
disk	I-Device
drives	I-Device
via	O
a	O
DB23F	B-Protocol
connector	O
.	O
</s>
<s>
The	O
then-standard	O
RS-232	O
serial	O
port	O
(	O
DB25M	B-Protocol
)	O
and	O
Centronics	O
parallel	B-Device
port	I-Device
(	O
DB25F	B-Protocol
)	O
are	O
also	O
included	O
.	O
</s>
<s>
The	O
system	O
displays	O
video	O
in	O
analog	O
RGB	O
PAL	B-Language
or	O
NTSC	O
through	O
a	O
proprietary	O
DB23M	O
connector	O
and	O
in	O
NTSC	O
mode	O
the	O
line	O
frequency	O
is	O
HSync	O
for	O
standard	O
video	O
modes	O
,	O
which	O
is	O
compatible	O
with	O
NTSC	O
television	O
and	O
CVBS/RGB	O
video	O
,	O
but	O
out	O
of	O
range	O
for	O
most	O
VGA-compatible	O
monitors	O
,	O
while	O
a	O
multisync	B-General_Concept
monitor	I-General_Concept
is	O
required	O
for	O
some	O
of	O
the	O
higher	O
resolutions	O
.	O
</s>
<s>
The	O
system	O
was	O
bundled	O
with	O
an	O
RF	O
adapter	O
to	O
provide	O
output	O
on	O
televisions	O
with	O
a	O
coaxial	O
RF	O
input	O
,	O
while	O
monochrome	O
video	O
is	O
available	O
via	O
an	O
RCA	B-Protocol
connector	I-Protocol
(	O
also	O
coaxial	O
)	O
.	O
</s>
<s>
On	O
the	O
left	O
side	O
,	O
behind	O
a	O
plastic	O
cover	O
,	O
there	O
is	O
a	O
Zorro	B-Device
(	O
Zorro	B-Device
I	O
)	O
bus	O
expansion	O
external	O
edge	O
connector	O
with	O
86	O
pins	O
.	O
</s>
<s>
Peripherals	O
such	O
as	O
a	O
hard	O
disk	O
drive	O
can	O
be	O
added	O
via	O
the	O
expansion	B-Device
slot	I-Device
and	O
are	O
configured	O
automatically	O
by	O
the	O
Amiga	B-Device
's	O
AutoConfig	B-Device
standard	O
,	O
so	O
that	O
multiple	O
devices	O
do	O
not	O
conflict	O
with	O
each	O
other	O
.	O
</s>
<s>
Up	O
to	O
of	O
so-called	O
"	O
fast	B-Device
RAM	I-Device
"	O
(	O
memory	O
that	O
can	O
be	O
accessed	O
by	O
the	O
CPU	B-General_Concept
only	O
)	O
can	O
be	O
added	O
using	O
the	O
side	O
expansion	B-Device
slot	I-Device
.	O
</s>
<s>
This	O
connector	O
is	O
electronically	O
identical	O
with	O
the	O
Amiga	B-Device
1000	I-Device
's	O
,	O
but	O
swapped	O
on	O
the	O
other	O
side	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
has	O
a	O
"	O
trap-door	O
"	O
slot	O
on	O
the	O
underside	O
for	O
a	O
RAM	B-Architecture
upgrade	O
(	O
typically	O
)	O
.	O
</s>
<s>
This	O
extra	O
RAM	B-Architecture
is	O
classified	O
as	O
"	O
fast	O
"	O
RAM	B-Architecture
,	O
but	O
is	O
sometimes	O
referred	O
to	O
as	O
"	O
slow	O
"	O
RAM	B-Architecture
:	O
due	O
to	O
the	O
design	O
of	O
the	O
expansion	B-Device
bus	I-Device
,	O
it	O
is	O
actually	O
on	O
the	O
chipset	O
bus	O
.	O
</s>
<s>
All	O
versions	O
of	O
the	O
A500	O
can	O
have	O
the	O
additional	O
RAM	B-Architecture
configured	O
as	O
chip	B-Device
RAM	I-Device
by	O
a	O
simple	O
hardware	O
modification	O
,	O
which	O
involves	O
fitting	O
a	O
later	O
model	O
(	O
8372A	O
)	O
Agnus	B-Device
chip	O
.	O
</s>
<s>
Likewise	O
,	O
all	O
versions	O
of	O
the	O
A500	O
can	O
be	O
upgraded	O
to	O
chip	B-Device
RAM	I-Device
by	O
fitting	O
the	O
chip	O
and	O
adding	O
additional	O
memory	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
also	O
sports	O
an	O
unusual	O
feature	O
for	O
a	O
budget	O
machine	O
,	O
socketed	O
chips	O
,	O
which	O
allow	O
easy	O
replacement	O
of	O
defective	O
chips	O
.	O
</s>
<s>
The	O
CPU	B-General_Concept
can	O
be	O
directly	O
upgraded	O
on	O
the	O
motherboard	O
to	O
a	O
68010	B-Device
;	O
or	O
to	O
a	O
68020	B-Device
,	O
68030	B-Device
,	O
or	O
68040	B-Device
via	O
the	O
side	O
expansion	B-Device
slot	I-Device
;	O
or	O
by	O
removing	O
the	O
CPU	B-General_Concept
and	O
plugging	O
a	O
CPU	B-General_Concept
expansion	B-Device
card	I-Device
into	O
the	O
CPU	B-General_Concept
socket	O
(	O
this	O
requires	O
opening	O
the	O
computer	O
and	O
thus	O
voided	O
any	O
remaining	O
warranty	O
)	O
.	O
</s>
<s>
In	O
fact	O
,	O
all	O
the	O
custom	O
chips	O
can	O
be	O
upgraded	O
to	O
the	O
Amiga	B-Device
Enhanced	I-Device
Chip	I-Device
Set	I-Device
(	O
ECS	B-Device
)	O
versions	O
.	O
</s>
<s>
OCS	B-Device
(	O
1.2	O
&	O
1.3	O
models	O
)	O
or	O
ECS	B-Device
(	O
1.3	O
and	O
500+	O
2.04	O
models	O
)	O
chipset	O
.	O
</s>
<s>
ECS	B-Device
revisions	O
of	O
the	O
chipset	O
made	O
PAL/NTSC	O
mode	O
switchable	O
in	O
software	O
.	O
</s>
<s>
512KB	O
of	O
chip	B-Device
RAM	I-Device
(	O
150ns	O
access	O
time	O
)	O
.	O
</s>
<s>
One	O
3.5	B-Device
"	I-Device
double-density	O
floppy	B-Device
disk	I-Device
drive	I-Device
is	O
built	O
in	O
,	O
which	O
is	O
completely	O
programmable	O
and	O
thus	O
can	O
read	O
IBM	B-Device
PC	I-Device
disks	O
,	O
standard	O
Amiga	B-Device
disks	O
,	O
and	O
up	O
to	O
with	O
custom	O
formatting	O
(	O
such	O
as	O
Klaus	O
Deppich	O
's	O
diskspare.device	O
)	O
.	O
</s>
<s>
PAL	B-Language
mode	O
:	O
768×580	O
maximum	O
(	O
overscan	O
interlaced	O
if	O
viewed	O
on	O
composite	O
monitor/TV	O
)	O
.	O
</s>
<s>
The	O
Amiga	B-Device
can	O
show	O
multiple	O
resolution	O
modes	O
at	O
the	O
same	O
time	O
,	O
splitting	O
the	O
screen	O
vertically	O
.	O
</s>
<s>
Planar	B-Device
graphics	O
are	O
used	O
,	O
with	O
up	O
to	O
5	O
bitplanes	O
(	O
4	O
in	O
hires	O
)	O
;	O
this	O
allowed	O
2	O
,	O
4	O
,	O
8	O
,	O
16	O
and	O
32	O
colour	O
screens	O
,	O
from	O
a	O
palette	O
of	O
4096	O
colours	O
.	O
</s>
<s>
This	O
works	O
by	O
letting	O
each	O
pixel	B-Algorithm
position	O
use	O
the	O
previous	O
RGB	O
value	O
and	O
modify	O
one	O
of	O
the	O
red	O
,	O
green	O
or	O
blue	O
values	O
to	O
a	O
new	O
4-bit	O
value	O
.	O
</s>
<s>
Using	O
various	O
expansion	O
techniques	O
,	O
the	O
A500	O
's	O
total	O
RAM	B-Architecture
can	O
reach	O
up	O
to	O
138MB	O
–	O
2MB	O
Chip	B-Device
RAM	I-Device
,	O
8MB	O
16-bit	O
Fast	B-Device
RAM	I-Device
,	O
and	O
128MB	O
32-bit	O
Fast	B-Device
RAM	I-Device
.	O
</s>
<s>
The	O
stock	O
512KB	O
Chip	B-Device
RAM	I-Device
can	O
be	O
complemented	O
by	O
512KB	O
using	O
a	O
"	O
trapdoor	O
"	O
expansion	O
(	O
Commodore	O
A501	O
or	O
compatible	O
)	O
.	O
</s>
<s>
While	O
that	O
expansion	O
memory	O
is	O
connected	O
to	O
the	O
chip	O
bus	O
,	O
hardware	O
limitations	O
of	O
early	O
stock	O
Agnus	B-Device
chip	O
revisions	O
prevent	O
its	O
use	O
as	O
Chip	B-Device
RAM	I-Device
,	O
only	O
the	O
CPU	B-General_Concept
can	O
access	O
it	O
.	O
</s>
<s>
Suffering	O
from	O
the	O
same	O
contention	O
limitations	O
as	O
Chip	B-Device
RAM	I-Device
,	O
that	O
memory	O
is	O
known	O
as	O
"	O
Slow	O
RAM	B-Architecture
"	O
or	O
"	O
Pseudo-fast	O
RAM	B-Architecture
"	O
.	O
</s>
<s>
Agnus	B-Device
revisions	O
shipped	O
with	O
late	O
A500	O
are	O
ECS	B-Device
and	O
allow	O
use	O
of	O
trapdoor	O
RAM	B-Architecture
as	O
real	O
Chip	B-Device
RAM	I-Device
for	O
a	O
total	O
1MB	O
.	O
</s>
<s>
after	O
changing	O
the	O
memory-layout	O
jumper	O
allows	O
use	O
of	O
trapdoor	O
RAM	B-Architecture
as	O
real	O
Chip	B-Device
RAM	I-Device
for	O
a	O
total	O
1MB	O
.	O
</s>
<s>
Using	O
a	O
Gary	O
adapter	O
,	O
that	O
memory	O
will	O
be	O
mapped	O
as	O
either	O
split	O
on	O
Chip	B-Device
RAM	I-Device
and	O
Slow	O
RAM	B-Architecture
or	O
fully	O
as	O
Slow	O
RAM	B-Architecture
,	O
depending	O
on	O
configuration	O
.	O
</s>
<s>
Furthermore	O
,	O
using	O
an	O
A3000	B-Device
Agnus	B-Device
on	O
an	O
adapter	O
board	O
,	O
it	O
is	O
possible	O
to	O
expand	O
the	O
Chip	B-Device
RAM	I-Device
to	O
2MB	O
,	O
matching	O
the	O
A500+	O
.	O
</s>
<s>
"	O
Fast	O
"	O
RAM	B-Architecture
is	O
located	O
on	O
the	O
CPU-side	O
bus	O
.	O
</s>
<s>
Its	O
access	O
is	O
exclusive	O
to	O
the	O
CPU	B-General_Concept
and	O
not	O
slowed	O
by	O
any	O
chipset	O
access	O
.	O
</s>
<s>
The	O
side	O
expansion	B-Device
port	I-Device
allows	O
for	O
up	O
to	O
8MB	O
of	O
Zorro-style	B-Device
expansion	O
RAM	B-Architecture
.	O
</s>
<s>
Alternatively	O
,	O
a	O
CPU	B-General_Concept
adapter	O
allows	O
for	O
internal	O
expansion	O
.	O
</s>
<s>
Internal	O
or	O
external	O
CPU	B-General_Concept
accelerators	O
often	O
include	O
their	O
own	O
expansion	O
memory	O
.	O
</s>
<s>
16-bit	O
CPUs	O
are	O
limited	O
by	O
the	O
24-bit	O
address	B-General_Concept
space	I-General_Concept
but	O
they	O
can	O
repurpose	O
otherwise	O
unused	O
memory	O
space	O
for	O
their	O
included	O
RAM	B-Architecture
.	O
</s>
<s>
32-bit	O
CPU	B-General_Concept
accelerators	O
are	O
n't	O
limited	O
by	O
24-bit	O
addressing	O
and	O
can	O
include	O
up	O
to	O
128MB	O
of	O
Fast	B-Device
RAM	I-Device
(	O
and	O
potentially	O
more	O
)	O
.	O
</s>
<s>
+Amiga	O
system	O
memory	O
map	O
Address	O
Size	O
in	O
KB	O
Description	O
0x00	O
0000	O
256	O
Chip	B-Device
RAM	I-Device
0x04	O
0000	O
256	O
Chip	B-Device
RAM	I-Device
(	O
A1000	B-Device
option	O
card	O
)	O
0x08	O
0000	O
512	O
Chip	B-Device
RAM	I-Device
expansion	O
0x10	O
0000	O
1024	O
Extended	O
Chip	B-Device
RAM	I-Device
for	O
ECS/AGA	O
0x20	O
0000	O
8192	O
Primary	O
auto-config	O
space	O
(	O
Fast	B-Device
RAM	I-Device
)	O
0xA0	O
0000	O
1984	O
Reserved	O
0xBF	O
D000	O
3.8	O
8520-B	B-Device
(	O
even-byte	O
addresses	O
)	O
0xBF	O
E001	O
3.8	O
8520-A	O
(	O
odd-byte	O
addresses	O
)	O
0xC0	O
0000	O
1536	O
Internal	O
expansion	O
memory	O
(	O
pseudo-fast	O
,	O
"	O
slow	O
"	O
RAM	B-Architecture
on	O
Amiga	B-Device
500	I-Device
)	O
0xD8	O
0000	O
256	O
Reserved	O
0xDC	O
0000	O
64	O
Real	O
time	O
clock	O
0xDD	O
0000	O
188	O
Reserved	O
0xDF	O
F000	O
4	O
Custom	O
chip	O
registers	O
0xE0	O
0000	O
512	O
Reserved	O
0xE8	O
0000	O
64	O
Zorro	B-Device
II	I-Device
auto-config	O
space	O
(	O
before	O
relocation	O
)	O
0xE9	O
0000	O
448	O
Secondary	O
auto-config	O
space	O
(	O
usually	O
64K	O
I/O	O
boards	O
)	O
0xF0	O
0000	O
512	O
512K	O
System	O
ROM	B-Device
(	O
reserved	O
for	O
extended	O
ROM	B-Device
image	O
e.g.	O
</s>
<s>
Analogue	O
RGB	O
PAL	B-Language
and	O
NTSC	O
video	O
output	O
,	O
provided	O
on	O
an	O
Amiga-specific	O
DB23M	O
video	B-Protocol
connector	I-Protocol
.	O
</s>
<s>
Can	O
drive	O
video	O
with	O
HSync	O
for	O
standard	O
Amiga	B-Device
video	O
modes	O
.	O
</s>
<s>
This	O
is	O
not	O
compatible	O
with	O
most	O
VGA	B-Protocol
monitors	I-Protocol
.	O
</s>
<s>
A	O
Multisync	B-General_Concept
monitor	I-General_Concept
is	O
required	O
for	O
some	O
higher	O
resolutions	O
.	O
</s>
<s>
An	O
RF	O
adapter	O
(	O
A520	B-Protocol
)	O
was	O
frequently	O
bundled	O
with	O
the	O
machine	O
to	O
provide	O
output	O
on	O
regular	O
televisions	O
or	O
on	O
composite	O
monitors	O
.	O
</s>
<s>
Expansion	B-Device
ports	I-Device
are	O
limited	O
to	O
a	O
side	O
expansion	B-Device
port	I-Device
and	O
a	O
trapdoor	O
expansion	O
on	O
the	O
underside	O
of	O
the	O
machine	O
.	O
</s>
<s>
The	O
casing	O
can	O
also	O
be	O
opened	O
up	O
(	O
voiding	O
the	O
warranty	O
)	O
,	O
all	O
larger	O
chips	O
are	O
socketed	O
rather	O
than	O
being	O
TH/SMD	O
soldered	O
directly	O
to	O
the	O
motherboard	O
,	O
so	O
they	O
can	O
be	O
replaced	O
by	O
hand	O
.	O
</s>
<s>
The	O
CPU	B-General_Concept
can	O
be	O
upgraded	O
to	O
a	O
Motorola	B-Device
68010	I-Device
directly	O
or	O
to	O
a	O
68020	B-Device
,	O
68030	B-Device
or	O
68040	B-Device
via	O
the	O
side	O
expansion	B-Device
slot	I-Device
or	O
a	O
CPU	B-General_Concept
socket	O
adapter	O
board	O
.	O
</s>
<s>
The	O
chip	B-Device
RAM	I-Device
can	O
be	O
upgraded	O
to	O
directly	O
on	O
the	O
motherboard	O
,	O
provided	O
a	O
Fat	B-Device
Agnus	I-Device
chip	O
is	O
also	O
installed	O
to	O
support	O
it	O
.	O
</s>
<s>
Likewise	O
,	O
all	O
the	O
custom	O
chips	O
can	O
be	O
upgraded	O
to	O
the	O
ECS	B-Device
chipset	O
.	O
</s>
<s>
The	O
A500+	O
model	O
instead	O
allowed	O
upgrading	O
by	O
trapdoor	O
chip	B-Device
RAM	I-Device
without	O
clock	O
,	O
but	O
there	O
was	O
no	O
visible	O
means	O
on	O
board	O
to	O
map	O
any	O
of	O
this	O
as	O
FAST	O
,	O
causing	O
incompatibility	O
with	O
some	O
stubbornly	O
coded	O
programs	O
.	O
</s>
<s>
There	O
were	O
modification	O
instructions	O
available	O
for	O
the	O
A500	O
to	O
solder	O
or	O
socket	O
another	O
RAM	B-Architecture
on	O
the	O
board	O
,	O
then	O
run	O
extra	O
address	O
lines	O
to	O
the	O
trapdoor	O
slot	O
to	O
accommodate	O
an	O
additional	O
of	O
fast	O
or	O
chip	B-Device
RAM	I-Device
depending	O
on	O
the	O
installed	O
chipset	O
.	O
</s>
<s>
Up	O
to	O
of	O
"	O
fast	B-Device
RAM	I-Device
"	O
can	O
be	O
added	O
via	O
the	O
side	O
expansion	B-Device
slot	I-Device
,	O
even	O
more	O
if	O
an	O
accelerator	B-General_Concept
with	O
a	O
non-EC	O
(	O
without	O
reduced	O
data/address	O
bus	O
)	O
processor	O
and	O
32-bit	O
RAM	B-Architecture
is	O
used	O
.	O
</s>
<s>
Hard	O
drive	O
and	O
other	O
peripherals	O
can	O
be	O
added	O
via	O
the	O
side	O
expansion	B-Device
slot	I-Device
.	O
</s>
<s>
Several	O
companies	O
provided	O
combined	O
CPU	B-General_Concept
,	O
memory	O
and	O
hard	O
drive	O
upgradesor	O
provided	O
chainable	O
expansions	O
that	O
extended	O
the	O
bus	O
as	O
they	O
were	O
addedas	O
there	O
is	O
only	O
one	O
side	O
expansion	B-Device
slot	I-Device
.	O
</s>
<s>
Expansions	O
are	O
configured	O
automatically	O
by	O
AutoConfig	B-Device
software	O
,	O
so	O
multiple	O
pieces	O
of	O
hardware	O
did	O
not	O
conflict	O
with	O
each	O
other	O
.	O
</s>
<s>
Medium	O
green	O
means	O
no	O
chip	B-Device
RAM	I-Device
found	O
or	O
is	O
damaged	O
.	O
</s>
<s>
Red	O
means	O
bad	O
kickstart-ROM	O
.	O
</s>
<s>
Yellow	O
means	O
the	O
CPU	B-General_Concept
has	O
crashed	O
(	O
no	O
trap	O
routine	O
or	O
trying	O
to	O
run	O
bad	O
code	O
)	O
or	O
a	O
bad	O
Zorro	B-Device
expansion	B-Device
card	I-Device
.	O
</s>
<s>
Blue	O
means	O
a	O
custom	O
chip	O
problem	O
(	O
Denise	O
,	O
Paula	O
,	O
or	O
Agnus	B-Device
)	O
.	O
</s>
<s>
Light	O
green	O
means	O
CIA	B-Device
problem	O
.	O
</s>
<s>
Light	O
gray	O
means	O
that	O
the	O
CIA	B-Device
might	O
be	O
defective	O
.	O
</s>
<s>
mean	O
there	O
is	O
a	O
ROM	B-Device
or	O
CIA	B-Device
problem	O
.	O
</s>
<s>
One	O
blink	O
means	O
the	O
keyboard	O
ROM	B-Device
has	O
a	O
checksum	O
error	O
.	O
</s>
<s>
Two	O
blinks	O
means	O
RAM	B-Architecture
failure	O
.	O
</s>
<s>
A	O
popular	O
expansion	O
for	O
the	O
Amiga	B-Device
500	I-Device
was	O
the	O
Amiga	B-Device
501	O
circuit	O
board	O
that	O
can	O
be	O
installed	O
underneath	O
the	O
computer	O
behind	O
a	O
plastic	O
cover	O
.	O
</s>
<s>
The	O
expansion	O
contains	O
RAM	B-Architecture
configured	O
by	O
default	O
as	O
"	O
Slow	O
RAM	B-Architecture
"	O
or	O
"	O
trap-door	O
RAM	B-Architecture
"	O
and	O
a	O
battery-backed	O
real-time	O
clock	O
(	O
RTC	O
)	O
.	O
</s>
<s>
The	O
512	O
KB	O
trap-door	O
RAM	B-Architecture
and	O
512	O
KB	O
of	O
original	O
chip	B-Device
RAM	I-Device
will	O
result	O
in	O
1	O
MB	O
of	O
total	O
memory	O
.	O
</s>
<s>
The	O
added	O
memory	O
is	O
known	O
as	O
"	O
Slow	O
RAM	B-Architecture
"	O
,	O
as	O
its	O
access	O
is	O
impacted	O
by	O
chip-bus	O
bandwidth	O
contention	O
,	O
while	O
the	O
chipset	O
is	O
not	O
actually	O
able	O
to	O
address	O
it	O
.	O
</s>
<s>
Later	O
revisions	O
of	O
the	O
motherboard	O
provide	O
solder-jumpers	O
to	O
relocate	O
the	O
trap-door	O
RAM	B-Architecture
to	O
the	O
chip	O
memory	O
pool	O
,	O
given	O
the	O
Agnus	B-Device
chip	O
is	O
the	O
newer	O
ECS	B-Device
version	O
,	O
shipped	O
in	O
later	O
A500	O
motherboards	O
.	O
</s>
<s>
Each	O
time	O
the	O
Amiga	B-Device
500	I-Device
is	O
booted	O
,	O
it	O
executes	O
code	O
from	O
the	O
Kickstart	B-Device
ROM	B-Device
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
initially	O
came	O
shipped	O
with	O
AmigaOS	B-Application
1.2	O
,	O
but	O
units	O
since	O
October	O
1988	O
had	O
version	O
1.3	O
installed	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
was	O
the	O
best-selling	O
model	O
in	O
the	O
Amiga	B-Device
family	O
of	O
computers	O
.	O
</s>
<s>
Owing	O
to	O
the	O
inexpensive	O
cost	O
of	O
the	O
Amiga	B-Device
500	I-Device
in	O
then	O
price-sensitive	O
Europe	O
,	O
sales	O
of	O
the	O
Amiga	B-Device
family	O
of	O
computers	O
were	O
strongest	O
there	O
,	O
constituting	O
85	O
percent	O
of	O
Commodore	O
's	O
total	O
sales	O
in	O
the	O
fourth	O
quarter	O
of	O
1990	O
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
was	O
widely	O
perceived	O
as	O
a	O
gaming	O
machine	O
and	O
the	O
Amiga	B-Device
2000	I-Device
a	O
computer	O
for	O
artists	O
and	O
hobbyists	O
.	O
</s>
<s>
However	O
,	O
Commodore	O
UK	O
refuted	O
that	O
figure	O
and	O
said	O
that	O
the	O
entire	O
Amiga	B-Device
line	O
sold	O
between	O
four	O
and	O
five	O
million	O
computers	O
.	O
</s>
<s>
Indeed	O
,	O
Ars	O
Technica	O
provides	O
a	O
year-by-year	O
graph	O
of	O
the	O
sales	O
of	O
all	O
Amiga	B-Device
computers	I-Device
.	O
</s>
<s>
The	O
Amiga	B-Device
500	I-Device
Plus	O
(	O
often	O
A500	O
Plus	O
or	O
simply	O
A500+	O
)	O
is	O
a	O
revised	O
version	O
of	O
the	O
original	O
Amiga	B-Device
500	I-Device
computer	O
.	O
</s>
<s>
It	O
was	O
notable	O
for	O
introducing	O
new	O
versions	O
of	O
Kickstart	B-Device
and	O
Workbench	B-Application
,	O
and	O
for	O
some	O
minor	O
improvements	O
in	O
the	O
custom	O
chips	O
,	O
known	O
as	O
the	O
Enhanced	B-Device
Chip	I-Device
Set	I-Device
(	O
or	O
ECS	B-Device
)	O
.	O
</s>
<s>
Although	O
officially	O
introduced	O
in	O
1992	O
,	O
some	O
Amiga	B-Device
500	I-Device
units	O
sold	O
in	O
late	O
1991	O
actually	O
featured	O
the	O
revised	O
motherboard	O
used	O
in	O
the	O
A500+	O
.	O
</s>
<s>
Although	O
the	O
Amiga	O
500+	O
was	O
an	O
improvement	O
to	O
the	O
Amiga	B-Device
500	I-Device
,	O
it	O
was	O
minor	O
.	O
</s>
<s>
It	O
was	O
discontinued	O
and	O
replaced	O
by	O
the	O
Amiga	B-Device
600	I-Device
in	O
summer	O
1992	O
,	O
making	O
it	O
the	O
shortest-lived	O
Amiga	B-Device
model	O
.	O
</s>
<s>
Due	O
to	O
the	O
new	O
Kickstart	B-Device
v2.04	O
,	O
quite	O
a	O
few	O
popular	O
games	O
(	O
such	O
as	O
Treasure	B-Application
Island	I-Application
Dizzy	I-Application
,	O
SWIV	B-Application
,	O
and	O
Lotus	O
Esprit	O
Turbo	O
Challenge	O
)	O
failed	O
to	O
work	O
on	O
the	O
Amiga	O
500+	O
,	O
and	O
some	O
people	O
took	O
them	O
back	O
to	O
dealers	O
demanding	O
an	O
original	O
Kickstart	B-Device
1.3	O
Amiga	B-Device
500	I-Device
.	O
</s>
<s>
This	O
problem	O
was	O
solved	O
by	O
third	O
parties	O
who	O
produced	O
Kickstart	B-Device
ROM	B-Device
switching	O
boards	O
,	O
that	O
could	O
allow	O
the	O
Amiga	O
500+	O
to	O
be	O
downgraded	O
to	O
Kickstart	B-Device
1.2	O
or	O
1.3	O
.	O
</s>
<s>
It	O
also	O
encouraged	O
game	O
developers	O
to	O
use	O
better	O
programming	O
habits	O
,	O
which	O
was	O
important	O
since	O
Commodore	O
already	O
had	O
plans	O
for	O
the	O
introduction	O
of	O
the	O
next-generation	O
Amiga	B-Application
1200	I-Application
computer	O
.	O
</s>
<s>
A	O
program	O
,	O
Relokick	O
,	O
was	O
also	O
released	O
(	O
and	O
included	O
with	O
an	O
issue	O
of	O
CU	O
Amiga	B-Device
)	O
which	O
loaded	O
a	O
Kickstart	B-Device
1.3	O
ROM	B-Device
image	O
into	O
memory	O
and	O
booted	O
the	O
machine	O
into	O
Kickstart	B-Device
1.3	O
,	O
allowing	O
incompatible	O
software	O
to	O
run	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
updated	O
compatible	O
versions	O
of	O
games	O
were	O
later	O
released	O
,	O
such	O
as	O
budget	O
versions	O
of	O
Lotus	O
1	O
and	O
SWIV	B-Application
.	O
</s>
<s>
Double	O
Dragon	O
2	O
by	O
Binary	O
Design	O
received	O
an	O
update	O
for	O
ECS	B-Device
machines	O
with	O
the	O
"	O
Amiga	B-Device
phase-alternated	O
linescan	O
version	O
4.01/ECS	O
"	O
.	O
</s>
<s>
This	O
solved	O
compatibility	O
issues	O
with	O
the	O
graphics	O
which	O
appeared	O
garbled	O
on	O
ECS	B-Device
machines	O
,	O
and	O
it	O
also	O
slashed	O
the	O
in-game	O
loading	O
times	O
from	O
around	O
20	O
seconds	O
to	O
just	O
over	O
6	O
.	O
</s>
