<s>
The	O
Intel	B-General_Concept
8080	I-General_Concept
(	O
"	O
eighty-eighty	O
"	O
)	O
is	O
the	O
second	O
8-bit	O
microprocessor	B-Architecture
designed	O
and	O
manufactured	O
by	O
Intel	O
.	O
</s>
<s>
It	O
first	O
appeared	O
in	O
April	O
1974	O
and	O
is	O
an	O
extended	O
and	O
enhanced	O
variant	O
of	O
the	O
earlier	O
8008	B-General_Concept
design	O
,	O
although	O
without	O
binary	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
<s>
Two	O
faster	O
variants	O
,	O
the	O
8080A-1	B-General_Concept
(	O
sometimes	O
referred	O
to	O
as	O
the	O
8080B	O
)	O
and	O
8080A-2	B-General_Concept
,	O
became	O
available	O
later	O
with	O
clock	O
frequency	O
limits	O
of	O
3.125MHz	O
and	O
2.63MHz	O
respectively	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
needs	O
two	O
support	O
chips	O
to	O
function	O
in	O
most	O
applications	O
:	O
the	O
i8224	O
clock	O
generator/driver	O
and	O
the	O
i8228	O
bus	O
controller	O
.	O
</s>
<s>
It	O
is	O
implemented	O
in	O
N-type	B-Algorithm
metal	I-Algorithm
–	I-Algorithm
oxide	I-Algorithm
–	I-Algorithm
semiconductor	I-Algorithm
logic	I-Algorithm
(	O
NMOS	B-Algorithm
)	O
using	O
non-saturated	O
enhancement	B-Algorithm
mode	I-Algorithm
transistors	O
as	O
loads	O
thus	O
demanding	O
a	O
+12V	O
and	O
a	O
−5V	O
voltage	O
in	O
addition	O
to	O
the	O
main	O
transistor	B-General_Concept
–	I-General_Concept
transistor	I-General_Concept
logic	I-General_Concept
(	O
TTL	B-General_Concept
)	O
compatible	O
+5V	O
.	O
</s>
<s>
Although	O
earlier	O
microprocessors	B-Architecture
were	O
commonly	O
used	O
in	O
mass-produced	O
devices	O
such	O
as	O
calculators	B-Application
,	O
cash	O
registers	B-General_Concept
,	O
computer	B-General_Concept
terminals	I-General_Concept
,	O
industrial	O
robots	O
,	O
and	O
other	O
applications	O
,	O
the	O
8080	B-General_Concept
saw	O
greater	O
success	O
in	O
a	O
wider	O
set	O
of	O
applications	O
,	O
and	O
is	O
largely	O
credited	O
with	O
starting	O
the	O
microcomputer	B-Architecture
industry	O
.	O
</s>
<s>
Several	O
factors	O
contributed	O
to	O
its	O
popularity	O
:	O
its	O
40-pin	O
package	O
made	O
it	O
easier	O
to	O
interface	O
than	O
the	O
18-pin	O
8008	B-General_Concept
,	O
and	O
also	O
made	O
its	O
data	B-General_Concept
bus	I-General_Concept
more	O
efficient	O
;	O
its	O
NMOS	B-Algorithm
implementation	O
gave	O
it	O
faster	O
transistors	O
than	O
those	O
of	O
the	O
P-type	B-Algorithm
metal	I-Algorithm
–	I-Algorithm
oxide	I-Algorithm
–	I-Algorithm
semiconductor	I-Algorithm
logic	I-Algorithm
(	O
PMOS	O
)	O
8008	B-General_Concept
,	O
while	O
also	O
simplifying	O
interfacing	B-Protocol
by	O
making	O
it	O
TTL-compatible	B-General_Concept
;	O
a	O
wider	O
variety	O
of	O
support	O
chips	O
were	O
available	O
;	O
its	O
instruction	B-General_Concept
set	I-General_Concept
was	O
enhanced	O
over	O
the	O
8008	B-General_Concept
;	O
and	O
its	O
full	O
16-bit	B-Device
address	B-Architecture
bus	I-Architecture
(	O
versus	O
the	O
14-bit	O
one	O
of	O
the	O
8008	B-General_Concept
)	O
enabled	O
it	O
to	O
access	O
64KB	O
of	O
memory	O
,	O
four	O
times	O
more	O
than	O
the	O
8008	B-General_Concept
's	O
range	O
of	O
16KB	O
.	O
</s>
<s>
It	O
was	O
used	O
in	O
the	O
Altair	B-Architecture
8800	I-Architecture
and	O
subsequent	O
S-100	B-Architecture
bus	I-Architecture
personal	O
computers	O
until	O
it	O
was	O
replaced	O
by	O
the	O
Z80	B-General_Concept
in	O
this	O
role	O
,	O
and	O
was	O
the	O
original	O
target	O
CPU	O
for	O
CP/M	B-Application
operating	I-Application
systems	I-Application
developed	O
by	O
Gary	O
Kildall	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
directly	O
influenced	O
the	O
later	O
x86	B-Operating_System
architecture	I-Operating_System
.	O
</s>
<s>
Intel	O
designed	O
the	O
8086	B-General_Concept
to	O
have	O
its	O
assembly	B-Language
language	I-Language
be	O
similar	O
enough	O
to	O
the	O
8080	B-General_Concept
,	O
with	O
most	O
instructions	O
mapping	O
directly	O
onto	O
each	O
other	O
,	O
that	O
transpiled	B-Language
8080	B-General_Concept
assembly	B-Language
code	I-Language
could	O
be	O
executed	O
on	O
the	O
8086	B-General_Concept
.	O
</s>
<s>
Microprocessor	B-Architecture
customers	O
were	O
reluctant	O
to	O
adopt	O
the	O
8008	B-General_Concept
because	O
of	O
limitations	O
such	O
as	O
the	O
single	O
addressing	O
mode	O
,	O
low	O
clock	O
speed	O
,	O
low	O
pin	O
count	O
,	O
and	O
small	O
on-chip	O
stack	B-Application
,	O
which	O
restricted	O
the	O
scale	O
and	O
complexity	O
of	O
software	O
.	O
</s>
<s>
There	O
were	O
several	O
proposed	O
designs	O
for	O
the	O
8080	B-General_Concept
,	O
ranging	O
from	O
simply	O
adding	O
stack	B-Application
instructions	O
to	O
the	O
8008	B-General_Concept
to	O
a	O
complete	O
departure	O
from	O
all	O
previous	O
Intel	O
architectures	O
.	O
</s>
<s>
Federico	O
Faggin	O
,	O
the	O
originator	O
of	O
the	O
8080	B-General_Concept
architecture	O
in	O
early	O
1972	O
,	O
proposed	O
the	O
chip	O
to	O
Intel	O
's	O
management	O
and	O
pushed	O
for	O
its	O
implementation	O
.	O
</s>
<s>
Shima	O
did	O
the	O
detailed	O
design	O
under	O
Faggin	O
's	O
direction	O
,	O
using	O
the	O
design	O
methodology	O
for	O
random	O
logic	O
with	O
silicon	O
gate	O
that	O
Faggin	O
had	O
created	O
for	O
the	O
4000	O
family	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
was	O
explicitly	O
designed	O
to	O
be	O
a	O
general-purpose	O
microprocessor	B-Architecture
for	O
a	O
larger	O
number	O
of	O
customers	O
.	O
</s>
<s>
Much	O
of	O
the	O
development	O
effort	O
was	O
spent	O
trying	O
to	O
integrate	O
the	O
functionalities	O
of	O
the	O
8008	B-General_Concept
's	O
supplemental	O
chips	O
into	O
one	O
package	O
.	O
</s>
<s>
It	O
was	O
decided	O
early	O
in	O
development	O
that	O
the	O
8080	B-General_Concept
was	O
not	O
to	O
be	O
binary-compatible	B-General_Concept
with	O
the	O
8008	B-General_Concept
,	O
instead	O
opting	O
for	O
source	B-General_Concept
compatibility	I-General_Concept
once	O
run	O
through	O
a	O
transpiler	B-Language
,	O
to	O
allow	O
new	O
software	O
to	O
not	O
be	O
subject	O
to	O
the	O
same	O
restrictions	O
as	O
the	O
8008	B-General_Concept
.	O
</s>
<s>
For	O
the	O
same	O
reason	O
,	O
as	O
well	O
as	O
the	O
expand	O
the	O
capabilities	O
of	O
stack-based	O
routines	O
and	O
interrupts	O
,	O
the	O
stack	B-Application
was	O
moved	O
to	O
external	O
memory	O
.	O
</s>
<s>
Noting	O
the	O
specialized	O
use	O
of	O
general-purpose	O
registers	B-General_Concept
by	O
programmers	O
in	O
mainframe	O
systems	O
,	O
Stanley	O
Mazor	O
,	O
the	O
chip	O
architect	O
,	O
decided	O
the	O
8080	B-General_Concept
's	O
registers	B-General_Concept
would	O
be	O
specialized	O
,	O
with	O
register	B-General_Concept
pairs	O
having	O
a	O
different	O
set	O
of	O
uses	O
.	O
</s>
<s>
After	O
the	O
regulation	O
of	O
NMOS	B-Algorithm
fabrication	O
,	O
a	O
prototype	O
of	O
the	O
8080	B-General_Concept
was	O
completed	O
in	O
January	O
1974	O
.	O
</s>
<s>
It	O
had	O
a	O
flaw	O
,	O
in	O
that	O
driving	O
with	O
standard	O
TTL	B-General_Concept
devices	O
increased	O
the	O
ground	O
voltage	O
because	O
high	O
current	O
flowed	O
into	O
the	O
narrow	O
line	O
.	O
</s>
<s>
Intel	O
had	O
already	O
produced	O
40,000	O
units	O
of	O
the	O
8080	B-General_Concept
at	O
the	O
direction	O
of	O
the	O
sales	O
section	O
before	O
Shima	O
characterized	O
the	O
prototype	O
.	O
</s>
<s>
It	O
was	O
released	O
as	O
requiring	O
Low-power	O
Schottky	O
TTL	B-General_Concept
(	O
LS	O
TTL	B-General_Concept
)	O
devices	O
.	O
</s>
<s>
The	O
8080A	B-General_Concept
fixed	O
this	O
flaw	O
.	O
</s>
<s>
Intel	O
offered	O
an	O
instruction	B-Application
set	I-Application
simulator	I-Application
for	O
the	O
8080	B-General_Concept
named	O
INTERP/80	O
to	O
run	O
compiled	O
PL/M	B-Language
programs	O
.	O
</s>
<s>
The	O
Intel	B-General_Concept
8080	I-General_Concept
is	O
the	O
successor	O
to	O
the	O
8008	B-General_Concept
.	O
</s>
<s>
It	O
uses	O
the	O
same	O
basic	O
instruction	B-General_Concept
set	I-General_Concept
and	O
register	B-General_Concept
model	O
as	O
the	O
8008	B-General_Concept
,	O
although	O
it	O
is	O
neither	O
source	B-General_Concept
code	I-General_Concept
compatible	I-General_Concept
nor	O
binary	B-General_Concept
code	I-General_Concept
compatible	I-General_Concept
with	O
its	O
predecessor	O
.	O
</s>
<s>
Every	O
instruction	O
in	O
the	O
8008	B-General_Concept
has	O
an	O
equivalent	O
instruction	O
in	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
The	O
8080	B-General_Concept
also	O
adds	O
16-bit	B-Device
operations	O
in	O
its	O
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
Whereas	O
the	O
8008	B-General_Concept
required	O
the	O
use	O
of	O
the	O
HL	O
register	B-General_Concept
pair	O
to	O
indirectly	O
access	O
its	O
14-bit	O
memory	O
space	O
,	O
the	O
8080	B-General_Concept
added	O
addressing	O
modes	O
to	O
allow	O
direct	O
access	O
to	O
its	O
full	O
16-bit	B-Device
memory	O
space	O
.	O
</s>
<s>
The	O
internal	O
7-level	O
push-down	O
call	B-General_Concept
stack	I-General_Concept
of	O
the	O
8008	B-General_Concept
was	O
replaced	O
by	O
a	O
dedicated	O
16-bit	B-Device
stack-pointer	O
(	O
SP	O
)	O
register	B-General_Concept
.	O
</s>
<s>
The	O
8080	B-General_Concept
's	O
40-pin	O
DIP	B-Algorithm
packaging	I-Algorithm
permits	O
it	O
to	O
provide	O
a	O
16-bit	B-Device
address	B-Architecture
bus	I-Architecture
and	O
an	O
8-bit	O
data	B-General_Concept
bus	I-General_Concept
,	O
enabling	O
access	O
to	O
64KiB	O
(	O
216	O
bytes	O
)	O
of	O
memory	O
.	O
</s>
<s>
The	O
processor	O
has	O
seven	O
8-bit	O
registers	B-General_Concept
(	O
A	O
,	O
B	O
,	O
C	B-Algorithm
,	O
D	O
,	O
E	O
,	O
H	O
,	O
and	O
L	O
)	O
,	O
where	O
A	O
is	O
the	O
primary	O
8-bit	O
accumulator	B-General_Concept
.	O
</s>
<s>
The	O
other	O
six	O
registers	B-General_Concept
can	O
be	O
used	O
as	O
either	O
individual	O
8-bit	O
registers	B-General_Concept
or	O
in	O
three	O
16-bit	B-Device
register	B-General_Concept
pairs	O
(	O
BC	O
,	O
DE	O
,	O
and	O
HL	O
,	O
referred	O
to	O
as	O
B	O
,	O
D	O
and	O
H	O
in	O
Intel	O
documents	O
)	O
depending	O
on	O
the	O
particular	O
instruction	O
.	O
</s>
<s>
Some	O
instructions	O
also	O
enable	O
the	O
HL	O
register	B-General_Concept
pair	O
to	O
be	O
used	O
as	O
a	O
(	O
limited	O
)	O
16-bit	B-Device
accumulator	B-General_Concept
.	O
</s>
<s>
A	O
pseudo-register	O
M	O
,	O
which	O
refers	O
to	O
the	O
dereferenced	O
memory	O
location	O
pointed	O
to	O
by	O
HL	O
,	O
can	O
be	O
used	O
almost	O
anywhere	O
other	O
registers	B-General_Concept
can	O
be	O
used	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
has	O
a	O
16-bit	B-Device
stack	B-General_Concept
pointer	I-General_Concept
to	O
memory	O
,	O
replacing	O
the	O
8008	B-General_Concept
's	O
internal	O
stack	B-Application
,	O
and	O
a	O
16-bit	B-Device
program	B-General_Concept
counter	I-General_Concept
.	O
</s>
<s>
The	O
processor	O
maintains	O
internal	O
flag	O
bits	O
(	O
a	O
status	B-General_Concept
register	I-General_Concept
)	O
,	O
which	O
indicate	O
the	O
results	O
of	O
arithmetic	O
and	O
logical	O
instructions	O
.	O
</s>
<s>
Sign	B-Algorithm
(	O
S	B-Algorithm
)	O
,	O
set	O
if	O
the	O
result	O
is	O
negative	O
.	O
</s>
<s>
Zero	B-Algorithm
(	O
Z	B-Algorithm
)	O
,	O
set	O
if	O
the	O
result	O
is	O
zero	B-Algorithm
.	O
</s>
<s>
Parity	B-General_Concept
(	O
P	B-General_Concept
)	O
,	O
set	O
if	O
the	O
number	O
of	O
1	O
bits	O
in	O
the	O
result	O
is	O
even	O
.	O
</s>
<s>
Auxiliary	B-Device
carry	I-Device
(	O
AC	B-Device
or	O
H	O
)	O
,	O
used	O
for	O
binary-coded	O
decimal	O
arithmetic	O
(	O
BCD	O
)	O
.	O
</s>
<s>
The	O
carry	B-Algorithm
bit	I-Algorithm
can	O
be	O
set	O
or	O
complemented	O
by	O
specific	O
instructions	O
.	O
</s>
<s>
The	O
flags	O
can	O
be	O
copied	O
as	O
a	O
group	O
to	O
the	O
accumulator	B-General_Concept
.	O
</s>
<s>
The	O
A	O
accumulator	B-General_Concept
and	O
the	O
flags	O
together	O
are	O
called	O
the	O
PSW	O
register	B-General_Concept
,	O
or	O
program	O
status	O
word	O
.	O
</s>
<s>
As	O
with	O
many	O
other	O
8-bit	O
processors	O
,	O
all	O
instructions	O
are	O
encoded	O
in	O
one	O
byte	O
(	O
including	O
register	B-General_Concept
numbers	O
,	O
but	O
excluding	O
immediate	O
data	O
)	O
,	O
for	O
simplicity	O
.	O
</s>
<s>
Like	O
more	O
advanced	O
processors	O
,	O
it	O
has	O
automatic	O
CALL	O
and	O
RET	O
instructions	O
for	O
multi-level	O
procedure	O
calls	O
and	O
returns	O
(	O
which	O
can	O
even	O
be	O
conditionally	O
executed	O
,	O
like	O
jumps	O
)	O
and	O
instructions	O
to	O
save	O
and	O
restore	O
any	O
16-bit	B-Device
register	B-General_Concept
pair	O
on	O
the	O
machine	O
stack	B-Application
.	O
</s>
<s>
These	O
are	O
intended	O
to	O
be	O
supplied	O
by	O
external	O
hardware	O
in	O
order	O
to	O
invoke	O
a	O
corresponding	O
interrupt	B-General_Concept
service	I-General_Concept
routine	I-General_Concept
,	O
but	O
are	O
also	O
often	O
employed	O
as	O
fast	O
system	B-Operating_System
calls	I-Operating_System
.	O
</s>
<s>
The	O
instruction	O
that	O
executes	O
slowest	O
is	O
,	O
which	O
is	O
used	O
for	O
exchanging	O
the	O
register	B-General_Concept
pair	O
HL	O
with	O
the	O
value	O
stored	O
at	O
the	O
address	O
indicated	O
by	O
the	O
stack	B-General_Concept
pointer	I-General_Concept
.	O
</s>
<s>
All	O
8-bit	O
operations	O
with	O
two	O
operands	O
can	O
only	O
be	O
performed	O
on	O
the	O
8-bit	O
accumulator	B-General_Concept
(	O
the	O
A	O
register	B-General_Concept
)	O
.	O
</s>
<s>
The	O
other	O
operand	O
can	O
be	O
either	O
an	O
immediate	O
value	O
,	O
another	O
8-bit	O
register	B-General_Concept
,	O
or	O
a	O
memory	O
byte	O
addressed	O
by	O
the	O
16-bit	B-Device
register	B-General_Concept
pair	O
HL	O
.	O
</s>
<s>
Increments	O
and	O
decrements	O
can	O
be	O
performed	O
on	O
any	O
8	O
bit	O
register	B-General_Concept
or	O
an	O
HL-addressed	O
memory	O
byte	O
.	O
</s>
<s>
Direct	O
copying	O
is	O
supported	O
between	O
any	O
two	O
8-bit	O
registers	B-General_Concept
and	O
between	O
any	O
8-bit	O
register	B-General_Concept
and	O
an	O
HL-addressed	O
memory	O
byte	O
.	O
</s>
<s>
Due	O
to	O
the	O
regular	O
encoding	O
of	O
the	O
instruction	O
(	O
using	O
a	O
quarter	O
of	O
available	O
opcode	O
space	O
)	O
,	O
there	O
are	O
redundant	O
codes	O
to	O
copy	O
a	O
register	B-General_Concept
into	O
itself	O
(	O
,	O
for	O
instance	O
)	O
,	O
which	O
are	O
of	O
little	O
use	O
,	O
except	O
for	O
delays	O
.	O
</s>
<s>
Although	O
the	O
8080	B-General_Concept
is	O
generally	O
an	O
8-bit	O
processor	O
,	O
it	O
has	O
limited	O
abilities	O
to	O
perform	O
16-bit	B-Device
operations	O
.	O
</s>
<s>
Any	O
of	O
the	O
three	O
16-bit	B-Device
register	B-General_Concept
pairs	O
(	O
BC	O
,	O
DE	O
,	O
or	O
HL	O
,	O
referred	O
to	O
as	O
B	O
,	O
D	O
,	O
H	O
in	O
Intel	O
documents	O
)	O
or	O
SP	O
can	O
be	O
loaded	O
with	O
an	O
immediate	O
16-bit	B-Device
value	O
(	O
using	O
)	O
,	O
incremented	O
or	O
decremented	O
(	O
using	O
and	O
)	O
,	O
or	O
added	O
to	O
HL	O
(	O
using	O
)	O
.	O
</s>
<s>
By	O
adding	O
HL	O
to	O
itself	O
,	O
it	O
is	O
possible	O
to	O
achieve	O
the	O
same	O
result	O
as	O
a	O
16-bit	B-Device
arithmetical	O
left	O
shift	O
with	O
one	O
instruction	O
.	O
</s>
<s>
The	O
only	O
16-bit	B-Device
instructions	O
that	O
affect	O
any	O
flag	O
is	O
,	O
which	O
sets	O
the	O
CY	O
(	O
carry	B-Algorithm
)	O
flag	O
in	O
order	O
to	O
allow	O
for	O
programmed	O
24-bit	O
or	O
32-bit	O
arithmetic	O
(	O
or	O
larger	O
)	O
,	O
needed	O
to	O
implement	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
.	O
</s>
<s>
A	O
stack	B-Application
frame	O
can	O
be	O
allocated	O
using	O
and	O
.	O
</s>
<s>
The	O
instruction	O
exchanges	O
the	O
values	O
of	O
the	O
HL	O
and	O
DE	O
register	B-General_Concept
pairs	O
.	O
</s>
<s>
exchanges	O
last	O
item	O
pushed	O
on	O
stack	B-Application
with	O
HL	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
supports	O
up	O
to	O
256	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
ports	O
,	O
accessed	O
via	O
dedicated	O
I/O	B-General_Concept
instructions	O
taking	O
port	O
addresses	O
as	O
operands	O
.	O
</s>
<s>
This	O
I/O	B-General_Concept
mapping	O
scheme	O
is	O
regarded	O
as	O
an	O
advantage	O
,	O
as	O
it	O
frees	O
up	O
the	O
processor	O
's	O
limited	O
address	O
space	O
.	O
</s>
<s>
Many	O
CPU	O
architectures	O
instead	O
use	O
so-called	O
memory-mapped	B-Architecture
I/O	I-Architecture
(	O
MMIO	B-Architecture
)	O
,	O
in	O
which	O
a	O
common	O
address	O
space	O
is	O
used	O
for	O
both	O
RAM	O
and	O
peripheral	O
chips	O
.	O
</s>
<s>
This	O
removes	O
the	O
need	O
for	O
dedicated	O
I/O	B-General_Concept
instructions	O
,	O
although	O
a	O
drawback	O
in	O
such	O
designs	O
may	O
be	O
that	O
special	O
hardware	O
must	O
be	O
used	O
to	O
insert	O
wait	O
states	O
,	O
as	O
peripherals	O
are	O
often	O
slower	O
than	O
memory	O
.	O
</s>
<s>
However	O
,	O
in	O
some	O
simple	O
8080	B-General_Concept
computers	O
,	O
I/O	B-General_Concept
is	O
indeed	O
addressed	O
as	O
if	O
they	O
were	O
memory	O
cells	O
,	O
"	O
memory-mapped	O
"	O
,	O
leaving	O
the	O
I/O	B-General_Concept
commands	O
unused	O
.	O
</s>
<s>
I/O	B-General_Concept
addressing	O
can	O
also	O
sometimes	O
employ	O
the	O
fact	O
that	O
the	O
processor	O
outputs	O
the	O
same	O
8-bit	O
port	O
address	O
to	O
both	O
the	O
lower	O
and	O
the	O
higher	O
address	O
byte	O
(	O
i.e.	O
,	O
would	O
put	O
the	O
address	O
0505h	O
on	O
the	O
16-bit	B-Device
address	B-Architecture
bus	I-Architecture
)	O
.	O
</s>
<s>
Similar	O
I/O	B-General_Concept
-port	O
schemes	O
are	O
used	O
in	O
the	O
backward-compatible	O
Zilog	B-General_Concept
Z80	I-General_Concept
and	O
Intel	B-General_Concept
8085	I-General_Concept
,	O
and	O
the	O
closely	O
related	O
x86	B-Operating_System
microprocessor	I-Operating_System
families	O
.	O
</s>
<s>
One	O
of	O
the	O
bits	O
in	O
the	O
processor	O
state	O
word	O
(	O
see	O
below	O
)	O
indicates	O
that	O
the	O
processor	O
is	O
accessing	O
data	O
from	O
the	O
stack	B-Application
.	O
</s>
<s>
Using	O
this	O
signal	O
,	O
it	O
is	O
possible	O
to	O
implement	O
a	O
separate	O
stack	B-General_Concept
memory	I-General_Concept
space	O
.	O
</s>
<s>
For	O
more	O
advanced	O
systems	O
,	O
during	O
one	O
phase	O
of	O
its	O
working	O
loop	O
,	O
the	O
processor	O
set	O
its	O
"	O
internal	O
state	O
byte	O
"	O
on	O
the	O
data	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
This	O
byte	O
contains	O
flags	O
that	O
determine	O
whether	O
the	O
memory	O
or	O
I/O	B-Architecture
port	I-Architecture
is	O
accessed	O
and	O
whether	O
it	O
is	O
necessary	O
to	O
handle	O
an	O
interrupt	O
.	O
</s>
<s>
For	O
simple	O
systems	O
,	O
where	O
the	O
interrupts	O
are	O
not	O
used	O
,	O
it	O
is	O
possible	O
to	O
find	O
cases	O
where	O
this	O
pin	O
is	O
used	O
as	O
an	O
additional	O
single-bit	O
output	O
port	O
(	O
the	O
popular	O
Radio-86RK	B-Device
computer	O
made	O
in	O
the	O
Soviet	O
Union	O
,	O
for	O
instance	O
)	O
.	O
</s>
<s>
The	O
following	O
8080/8085	O
assembler	B-Language
source	O
code	O
is	O
for	O
a	O
subroutine	O
named	O
that	O
copies	O
a	O
block	O
of	O
data	O
bytes	O
of	O
a	O
given	O
size	O
from	O
one	O
location	O
to	O
another	O
.	O
</s>
<s>
The	O
data	O
block	O
is	O
copied	O
one	O
byte	O
at	O
a	O
time	O
,	O
and	O
the	O
data	O
movement	O
and	O
looping	O
logic	O
utilizes	O
16-bit	B-Device
operations	O
.	O
</s>
<s>
rz	O
;	O
Return	O
if	O
the	O
zero-flag	O
is	O
set	O
high	O
.	O
</s>
<s>
ora	O
c	B-Algorithm
;	O
A	O
=	O
A	O
|	O
C	B-Algorithm
(	O
are	O
both	O
B	O
and	O
C	B-Algorithm
zero	B-Algorithm
?	O
)	O
</s>
<s>
jnz	O
loop	O
;	O
Jump	O
to	O
'	O
loop	O
:	O
'	O
if	O
the	O
zero-flag	O
is	O
not	O
set	O
.	O
</s>
<s>
The	O
address	B-Architecture
bus	I-Architecture
has	O
its	O
own	O
16	O
pins	O
,	O
and	O
the	O
data	B-General_Concept
bus	I-General_Concept
has	O
8	O
pins	O
that	O
are	O
usable	O
without	O
any	O
multiplexing	O
.	O
</s>
<s>
Using	O
the	O
two	O
additional	O
pins	O
(	O
read	O
and	O
write	O
signals	O
)	O
,	O
it	O
is	O
possible	O
to	O
assemble	O
simple	O
microprocessor	B-Architecture
devices	O
very	O
easily	O
.	O
</s>
<s>
The	O
pin-out	O
table	O
,	O
from	O
the	O
chip	O
's	O
accompanying	O
documentation	O
,	O
describes	O
the	O
pins	O
as	O
follows	O
:	O
</s>
<s>
Bidirectional	O
data	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
The	O
content	O
of	O
other	O
processor	B-General_Concept
registers	I-General_Concept
is	O
not	O
modified	O
.	O
</s>
<s>
The	O
processor	O
is	O
requested	O
to	O
switch	O
the	O
data	O
and	O
address	B-Architecture
bus	I-Architecture
to	O
the	O
high	O
impedance	O
(	O
"	O
disconnected	O
"	O
)	O
state	O
.	O
</s>
<s>
This	O
is	O
an	O
inverted	O
output	O
,	O
the	O
active	O
level	O
being	O
logical	O
zero	B-Algorithm
.	O
</s>
<s>
Output	O
Active	O
level	O
indicates	O
that	O
the	O
processor	O
has	O
put	O
the	O
"	O
state	O
word	O
"	O
on	O
the	O
data	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
This	O
signal	O
is	O
required	O
to	O
pass	O
through	O
additional	O
logic	O
before	O
it	O
can	O
be	O
used	O
to	O
write	O
the	O
processor	O
state	O
word	O
from	O
the	O
data	B-General_Concept
bus	I-General_Concept
into	O
some	O
external	O
register	B-General_Concept
,	O
e.g.	O
,	O
8238-System	O
Controller	O
and	O
Bus	O
Driver	O
.	O
</s>
<s>
With	O
this	O
signal	O
it	O
is	O
possible	O
to	O
suspend	O
the	O
processor	O
's	O
work	O
.	O
</s>
<s>
A	O
key	O
factor	O
in	O
the	O
success	O
of	O
the	O
8080	B-General_Concept
was	O
the	O
broad	O
range	O
of	O
support	O
chips	O
available	O
,	O
providing	O
serial	O
communications	O
,	O
counter/timing	O
,	O
input/output	B-General_Concept
,	O
direct	O
memory	O
access	O
,	O
and	O
programmable	O
interrupt	O
control	O
amongst	O
other	O
functions	O
:	O
</s>
<s>
The	O
8080	B-General_Concept
integrated	O
circuit	O
uses	O
non-saturated	O
enhancement-load	O
nMOS	B-Algorithm
gates	O
,	O
demanding	O
extra	O
voltages	O
(	O
for	O
the	O
load-gate	O
bias	O
)	O
.	O
</s>
<s>
A	O
single	O
layer	O
of	O
metal	O
is	O
used	O
to	O
interconnect	B-Protocol
the	O
approximately	O
4,500	O
transistors	O
in	O
the	O
design	O
,	O
but	O
the	O
higher	O
resistance	O
polysilicon	O
layer	O
,	O
which	O
required	O
higher	O
voltage	O
for	O
some	O
interconnects	B-General_Concept
,	O
is	O
implemented	O
with	O
transistor	O
gates	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
is	O
used	O
in	O
many	O
early	O
microcomputers	B-Architecture
,	O
such	O
as	O
the	O
MITS	B-Architecture
Altair	I-Architecture
8800	I-Architecture
Computer	O
,	O
Processor	O
Technology	O
SOL-20	B-Architecture
Terminal	O
Computer	O
and	O
IMSAI	B-Device
8080	I-Device
Microcomputer	B-Architecture
,	O
forming	O
the	O
basis	O
for	O
machines	O
running	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
(	O
the	O
later	O
,	O
almost	O
fully	O
compatible	O
and	O
more	O
able	O
,	O
Zilog	B-General_Concept
Z80	I-General_Concept
processor	O
would	O
capitalize	O
on	O
this	O
,	O
with	O
Z80	B-General_Concept
and	O
CP/M	B-Application
becoming	O
the	O
dominant	O
CPU	O
and	O
OS	O
combination	O
of	O
the	O
period	O
circa	O
1976	O
to	O
1983	O
much	O
as	O
did	O
the	O
x86	B-Operating_System
and	O
DOS	B-Device
for	O
the	O
PC	B-Device
a	O
decade	O
later	O
)	O
.	O
</s>
<s>
In	O
1979	O
,	O
even	O
after	O
the	O
introduction	O
of	O
the	O
Z80	B-General_Concept
and	O
8085	B-General_Concept
processors	O
,	O
five	O
manufacturers	O
of	O
the	O
8080	B-General_Concept
were	O
selling	O
an	O
estimated	O
500,000	O
units	O
per	O
month	O
at	O
a	O
price	O
around	O
$3	O
to	O
$4	O
each	O
.	O
</s>
<s>
The	O
first	O
single-board	O
microcomputers	B-Architecture
,	O
such	O
as	O
MYCRO-1	B-Device
and	O
the	O
dyna-micro	O
/	O
MMD-1	O
(	O
see	O
:	O
Single-board	B-Device
computer	I-Device
)	O
were	O
based	O
on	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
.	O
</s>
<s>
One	O
of	O
the	O
early	O
uses	O
of	O
the	O
8080	B-General_Concept
was	O
made	O
in	O
the	O
late	O
1970s	O
by	O
Cubic-Western	O
Data	O
of	O
San	O
Diego	O
,	O
California	O
,	O
in	O
its	O
Automated	O
Fare	O
Collection	O
Systems	O
custom	O
designed	O
for	O
mass	O
transit	O
systems	O
around	O
the	O
world	O
.	O
</s>
<s>
An	O
early	O
industrial	O
use	O
of	O
the	O
8080	B-General_Concept
is	O
as	O
the	O
"	O
brain	O
"	O
of	O
the	O
DatagraphiX	O
Auto-COM	O
(	O
Computer	O
Output	O
Microfiche	O
)	O
line	O
of	O
products	O
which	O
takes	O
large	O
amounts	O
of	O
user	O
data	O
from	O
reel-to-reel	O
tape	O
and	O
images	O
it	O
onto	O
microfiche	O
.	O
</s>
<s>
Several	O
early	O
video	O
arcade	O
games	O
were	O
built	O
around	O
the	O
8080	B-General_Concept
microprocessor	I-General_Concept
.	O
</s>
<s>
The	O
first	O
commercially-available	O
arcade	O
video	O
game	O
to	O
incorporate	O
a	O
microprocessor	B-Architecture
was	O
Gun	B-Application
Fight	I-Application
,	O
Midway	O
Games	O
 '	O
8080-based	O
reimplementation	O
of	O
Taito	O
's	O
discrete-logic	O
Western	B-Application
Gun	I-Application
,	O
which	O
was	O
released	O
in	O
November	O
1975	O
.	O
</s>
<s>
(	O
A	O
pinball	O
machine	O
which	O
incorporated	O
a	O
Motorola	B-Device
6800	I-Device
processor	O
,	O
The	O
Spirit	O
of	O
'	O
76	O
,	O
had	O
already	O
been	O
released	O
the	O
previous	O
month	O
.	O
)	O
</s>
<s>
The	O
8080	B-General_Concept
was	O
then	O
used	O
in	O
later	O
Midway	O
arcade	O
video	O
games	O
and	O
in	O
Taito	O
's	O
1978	O
Space	B-Application
Invaders	I-Application
,	O
one	O
of	O
the	O
most	O
successful	O
and	O
well-known	O
of	O
all	O
arcade	O
video	O
games	O
.	O
</s>
<s>
Zilog	O
introduced	O
the	O
Z80	B-General_Concept
,	O
which	O
has	O
a	O
compatible	O
machine	B-Language
language	I-Language
instruction	B-General_Concept
set	I-General_Concept
and	O
initially	O
used	O
the	O
same	O
assembly	B-Language
language	I-Language
as	O
the	O
8080	B-General_Concept
,	O
but	O
for	O
legal	O
reasons	O
,	O
Zilog	O
developed	O
a	O
syntactically-different	O
(	O
but	O
code	O
compatible	O
)	O
alternative	O
assembly	B-Language
language	I-Language
for	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
At	O
Intel	O
,	O
the	O
8080	B-General_Concept
was	O
followed	O
by	O
the	O
compatible	O
and	O
electrically	O
more	O
elegant	O
8085	B-General_Concept
.	O
</s>
<s>
Later	O
,	O
Intel	O
issued	O
the	O
assembly-language	O
compatible	O
(	O
but	O
not	O
binary-compatible	B-General_Concept
)	O
16-bit	B-Device
8086	B-General_Concept
and	O
then	O
the	O
8/16	O
-bit	O
8088	B-Device
,	O
which	O
was	O
selected	O
by	O
IBM	O
for	O
its	O
new	O
PC	B-Device
to	O
be	O
launched	O
in	O
1981	O
.	O
</s>
<s>
Later	O
NEC	O
made	O
the	O
NEC	B-Device
V20	I-Device
(	O
an	O
8088	B-Device
clone	O
with	O
Intel	B-Device
80186	I-Device
instruction	B-General_Concept
set	I-General_Concept
compatibility	O
)	O
which	O
also	O
supports	O
an	O
8080	B-General_Concept
emulation	O
mode	O
.	O
</s>
<s>
This	O
is	O
also	O
supported	O
by	O
NEC	O
's	O
V30	B-Device
(	O
a	O
similarly	O
enhanced	O
8086	B-General_Concept
clone	O
)	O
.	O
</s>
<s>
Thus	O
,	O
the	O
8080	B-General_Concept
,	O
via	O
its	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
,	O
made	O
a	O
lasting	O
impact	O
on	O
computer	O
history	O
.	O
</s>
<s>
A	O
number	O
of	O
processors	O
compatible	O
with	O
the	O
Intel	B-General_Concept
8080A	I-General_Concept
were	O
manufactured	O
in	O
the	O
Eastern	O
Bloc	O
:	O
the	O
KR580VM80A	O
(	O
initially	O
marked	O
as	O
КР580ИК80	O
)	O
in	O
the	O
Soviet	O
Union	O
,	O
the	O
MCY7880	B-General_Concept
made	O
by	O
Unitra	O
CEMI	O
in	O
Poland	O
,	O
the	O
MHB8080A	B-General_Concept
made	O
by	O
TESLA	O
in	O
Czechoslovakia	O
,	O
the	O
8080APC	O
made	O
by	O
Tungsram	O
/	O
MEV	O
in	O
Hungary	O
,	O
and	O
the	O
MMN8080	O
made	O
by	O
Microelectronica	O
Bucharest	O
in	O
Romania	O
.	O
</s>
<s>
,	O
the	O
8080	B-General_Concept
is	O
still	O
in	O
production	O
at	O
Lansdale	O
Semiconductors	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
also	O
changed	O
how	O
computers	O
were	O
created	O
.	O
</s>
<s>
When	O
the	O
8080	B-General_Concept
was	O
introduced	O
,	O
computer	O
systems	O
were	O
usually	O
created	O
by	O
computer	O
manufacturers	O
such	O
as	O
Digital	O
Equipment	O
Corporation	O
,	O
Hewlett-Packard	O
,	O
or	O
IBM	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
was	O
designed	O
for	O
almost	O
any	O
application	O
except	O
a	O
complete	O
computer	O
system	O
.	O
</s>
<s>
Hewlett-Packard	O
developed	O
the	O
HP	B-General_Concept
2640	I-General_Concept
series	O
of	O
smart	O
terminals	O
around	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
The	O
HP	B-General_Concept
2647	I-General_Concept
is	O
a	O
terminal	O
which	O
runs	O
the	O
programming	O
language	O
BASIC	O
on	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
Microsoft	O
's	O
founding	O
product	O
,	O
Microsoft	B-Language
BASIC	I-Language
,	O
was	O
originally	O
programmed	O
for	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
The	O
8080	B-General_Concept
and	O
8085	B-General_Concept
gave	O
rise	O
to	O
the	O
8086	B-General_Concept
,	O
which	O
was	O
designed	O
as	O
a	O
source	B-General_Concept
code	I-General_Concept
compatible	I-General_Concept
,	O
albeit	O
not	O
binary	B-General_Concept
compatible	I-General_Concept
,	O
extension	O
of	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
This	O
design	O
,	O
in	O
turn	O
,	O
later	O
spawned	O
the	O
x86	B-Operating_System
family	O
of	O
chips	O
,	O
which	O
continue	O
to	O
be	O
Intel	O
's	O
primary	O
line	O
of	O
processors	O
.	O
</s>
<s>
Many	O
of	O
the	O
8080	B-General_Concept
's	O
core	O
machine	B-Language
instructions	I-Language
and	O
concepts	O
survive	O
in	O
the	O
widespread	O
x86	B-Operating_System
platform	O
.	O
</s>
<s>
Examples	O
include	O
the	O
registers	B-General_Concept
named	O
A	O
,	O
B	O
,	O
C	B-Algorithm
,	O
and	O
D	O
and	O
many	O
of	O
the	O
flags	O
used	O
to	O
control	O
conditional	O
jumps	O
.	O
</s>
<s>
8080	B-General_Concept
assembly	B-Language
code	I-Language
can	O
still	O
be	O
directly	O
translated	O
into	O
x86	B-Operating_System
instructions	O
,	O
since	O
all	O
of	O
its	O
core	O
elements	O
are	O
still	O
present	O
.	O
</s>
<s>
Asteroid	O
8080	B-General_Concept
Intel	O
is	O
named	O
as	O
a	O
pun	O
and	O
praise	O
on	O
the	O
name	O
of	O
Intel	B-General_Concept
8080	I-General_Concept
.	O
</s>
<s>
Microsoft	O
's	O
published	O
phone	O
number	O
,	O
425-882-8080	O
,	O
was	O
chosen	O
because	O
much	O
early	O
work	O
was	O
on	O
this	O
chip	O
.	O
</s>
