<s>
The	O
MOS	B-General_Concept
Technology	I-General_Concept
65xx	I-General_Concept
series	O
is	O
a	O
family	O
of	O
8-bit	O
microprocessors	B-Architecture
from	O
MOS	B-Architecture
Technology	I-Architecture
,	O
based	O
on	O
the	O
Motorola	B-Device
6800	I-Device
(	O
introduced	O
ca	O
.	O
</s>
<s>
The	O
most	O
prolific	O
65xx	B-General_Concept
part	O
was	O
the	O
6502	B-General_Concept
,	O
used	O
in	O
home	O
computers	O
such	O
as	O
the	O
PET	B-Device
,	O
VIC-20	B-Device
,	O
Apple	B-Device
II	I-Device
,	O
Atari	B-Device
8-bit	I-Device
family	I-Device
,	O
and	O
BBC	B-Device
Micro	I-Device
.	O
</s>
<s>
The	O
6501	B-General_Concept
and	O
6502	B-General_Concept
have	O
40-pin	O
DIP	B-Algorithm
packages	O
;	O
the	O
6503	O
,	O
6504	O
,	O
6505	O
,	O
and	O
6507	B-General_Concept
are	O
28-pin	O
DIP	B-Algorithm
versions	O
,	O
for	O
reduced	O
chip	O
and	O
circuit	O
board	O
cost	O
.	O
</s>
<s>
The	O
omission	O
of	O
four	O
address	O
pins	O
reduces	O
the	O
external	O
addressability	O
to	O
4KB	O
(	O
from	O
the	O
64KB	O
of	O
the	O
6502	B-General_Concept
)	O
,	O
though	O
the	O
internal	O
PC	O
register	O
and	O
all	O
effective	O
address	O
calculations	O
remain	O
16-bit	B-Device
.	O
</s>
<s>
The	O
6507	B-General_Concept
omits	O
both	O
interrupt	O
pins	O
in	O
order	O
to	O
include	O
address	O
line	O
A12	O
,	O
providing	O
8	O
KB	O
of	O
external	O
addressability	O
but	O
no	O
interrupt	O
capability	O
.	O
</s>
<s>
The	O
6507	B-General_Concept
was	O
used	O
in	O
the	O
popular	O
Atari	B-General_Concept
2600	I-General_Concept
video	O
game	O
console	O
,	O
the	O
design	O
of	O
which	O
divides	O
the	O
8	O
KB	O
memory	O
space	O
in	O
half	O
,	O
allocating	O
the	O
lower	O
half	O
to	O
the	O
console	O
's	O
internal	O
RAM	O
and	O
peripherals	O
,	O
and	O
the	O
upper	O
half	O
to	O
the	O
Game	O
Cartridge	O
,	O
so	O
Atari	B-General_Concept
2600	I-General_Concept
cartridges	O
have	O
a	O
4	O
KB	O
address	O
limit	O
(	O
and	O
the	O
same	O
capacity	O
limit	O
unless	O
the	O
cartridge	O
contains	O
bank	B-General_Concept
switching	I-General_Concept
circuitry	O
)	O
.	O
</s>
<s>
One	O
popular	O
6502-based	O
computer	O
,	O
the	O
Commodore	O
64	O
,	O
used	O
a	O
modified	O
6502	B-General_Concept
CPU	O
,	O
the	O
6510	B-General_Concept
.	O
</s>
<s>
Unlike	O
the	O
65036505	O
and	O
6507	B-General_Concept
,	O
the	O
6510	B-General_Concept
is	O
a	O
40-pin	O
chip	O
that	O
adds	O
internal	O
hardware	O
:	O
an	O
8-bit	O
parallel	O
I/O	O
port	O
mapped	O
to	O
addresses	O
0000	O
and	O
0001	O
.	O
</s>
<s>
The	O
6508	B-General_Concept
is	O
another	O
chip	O
that	O
,	O
like	O
the	O
6510	B-General_Concept
,	O
adds	O
internal	O
hardware	O
:	O
256	O
bytes	O
of	O
SRAM	B-Architecture
and	O
the	O
same	O
8-bit	O
I/O	O
port	O
featured	O
by	O
the	O
6510	B-General_Concept
.	O
</s>
<s>
Though	O
these	O
chips	O
do	O
not	O
have	O
reduced	O
pin	O
counts	O
compared	O
to	O
the	O
6502	B-General_Concept
,	O
they	O
need	O
8	O
new	O
pins	O
for	O
the	O
added	O
parallel	O
I/O	O
port	O
.	O
</s>
