<s>
The	O
Z80000	B-Device
is	O
Zilog	O
's	O
32-bit	O
processor	B-General_Concept
,	O
first	O
released	O
in	O
1986	O
.	O
</s>
<s>
It	O
is	O
essentially	O
a	O
32-bit	O
expansion	O
of	O
its	O
16-bit	B-Device
predecessor	O
,	O
the	O
Zilog	B-Device
Z8000	I-Device
.	O
</s>
<s>
It	O
includes	O
multiprocessing	B-Operating_System
capability	O
,	O
a	O
six-stage	O
instruction	B-General_Concept
pipeline	I-General_Concept
,	O
and	O
a	O
256-byte	O
cache	B-General_Concept
.	O
</s>
<s>
Its	O
memory	B-General_Concept
addressing	I-General_Concept
system	O
can	O
access	O
4gigabytes	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
It	O
can	O
execute	O
code	O
written	O
for	O
the	O
Z8000	B-Device
,	O
but	O
is	O
not	O
compatible	O
with	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
Described	O
at	O
the	O
time	O
as	O
a	O
"	O
mainframe	B-Architecture
on	O
a	O
chip	O
"	O
,	O
the	O
processor	B-General_Concept
is	O
in	O
many	O
ways	O
an	O
equivalent	O
to	O
Intel	O
's	O
80386	B-General_Concept
.	O
</s>
<s>
Delays	O
in	O
the	O
initial	O
manufacturing	O
pushed	O
back	O
its	O
availability	O
date	O
to	O
after	O
that	O
of	O
the	O
386	B-General_Concept
,	O
and	O
the	O
Z80000	B-Device
saw	O
little	O
use	O
in	O
the	O
market	O
.	O
</s>
<s>
Like	O
the	O
Z8000	B-Device
it	O
is	O
based	O
on	O
,	O
the	O
Z80000	B-Device
has	O
sixteen	O
general-purpose	O
registers	B-General_Concept
,	O
but	O
expanded	O
from	O
the	O
Z8000	B-Device
's	O
16-bit	B-Device
to	O
32-bit	O
.	O
</s>
<s>
Like	O
the	O
Z8000	B-Device
,	O
the	O
Z80000	B-Device
allows	O
its	O
registers	B-General_Concept
to	O
be	O
combined	O
,	O
in	O
this	O
case	O
using	O
two	O
32-bit	O
registers	B-General_Concept
to	O
act	O
as	O
a	O
single	O
64-bit	O
one	O
.	O
</s>
<s>
To	O
support	O
the	O
Z8000s	B-Device
16-bit	B-Device
wide	O
data	O
,	O
the	O
Z80000	B-Device
can	O
place	O
two	O
16-bit	B-Device
values	O
in	O
a	O
single	O
32-register	O
.	O
</s>
<s>
The	O
processor	B-General_Concept
includes	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
that	O
provides	O
protected	B-General_Concept
memory	I-General_Concept
,	O
important	O
for	O
multitasking	B-Operating_System
,	O
and	O
virtual	B-Architecture
memory	I-Architecture
addressing	O
for	O
temporary	O
storage	O
of	O
RAM	B-Architecture
on	O
a	O
hard	B-Device
disk	I-Device
.	O
</s>
<s>
The	O
processor	B-General_Concept
has	O
three	O
methods	O
of	O
accessing	O
memory	O
:	O
</s>
<s>
compact	O
mode	O
–	O
meant	O
for	O
small	O
programs	O
,	O
could	O
only	O
access	O
64KB	O
(	O
16-bit	B-Device
addresses	O
,	O
equivalent	O
to	O
the	O
Z8000	B-Device
's	O
non-segmented	O
mode	O
)	O
.	O
</s>
<s>
segmented	O
mode	O
–	O
32,768	O
segments	O
of	O
64KB	O
(	O
16-bit	B-Device
address	O
;	O
comprising	O
memory	O
from	O
0-2GB	O
)	O
and	O
128	O
segments	O
of	O
16MB	O
(	O
24-bit	O
address	O
;	O
comprising	O
memory	O
from	O
2GB-4GB	O
)	O
,	O
making	O
a	O
total	O
of	O
4GB	O
(	O
32-bit	O
address	O
)	O
of	O
accessible	O
memory	O
.	O
</s>
<s>
The	O
processor	B-General_Concept
is	O
designed	O
to	O
interoperate	O
with	O
other	O
integrated	O
circuits	O
designed	O
for	O
use	O
with	O
the	O
Z8000	B-Device
,	O
such	O
as	O
the	O
Zilog	O
Z8070	O
floating-point	B-Algorithm
coprocessor	B-General_Concept
.	O
</s>
<s>
The	O
Z320	O
was	O
the	O
CMOS	B-Device
version	O
of	O
the	O
Z80000	B-Device
.	O
</s>
<s>
Segmented	O
addresses	O
restrict	O
effective	O
address	O
computations	O
to	O
the	O
specified	O
segment	O
of	O
the	O
base	O
pointer	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
Note	O
that	O
the	O
base	O
address	B-General_Concept
register	I-General_Concept
(	O
not	O
index	O
registers	B-General_Concept
!	O
)	O
</s>
