<s>
The	O
Commodore	O
D9060/D9090	O
Hard	B-Device
Disks	I-Device
were	O
the	O
only	O
family	O
of	O
hard	B-Device
drives	I-Device
that	O
Commodore	O
made	O
for	O
both	O
the	O
home	O
and	O
business	O
market	O
.	O
</s>
<s>
The	O
electronics	O
are	O
identical	O
in	O
the	O
D9060	O
and	O
the	O
larger	O
D9090	O
unit	O
;	O
the	O
only	O
difference	O
is	O
the	O
size	O
of	O
the	O
installed	O
hard	B-Device
drive	I-Device
,	O
with	O
a	O
jumper	O
set	O
to	O
distinguish	O
between	O
4	O
or	O
6	O
disk	B-Device
heads	I-Device
.	O
</s>
<s>
Originally	O
intended	O
for	O
the	O
metal-cased	O
PET/CBM	O
series	O
of	O
computers	O
,	O
they	O
are	O
compatible	O
with	O
the	O
VIC-20	B-Device
,	O
Commodore	O
64	O
and	O
later	O
models	O
with	O
an	O
adapter	O
.	O
</s>
<s>
on	O
the	O
D9060	O
;	O
153	O
Cylinders	O
×	O
4	O
Heads	B-Device
×	O
32	O
Sectors	O
×	O
256	O
Bytes/sector	O
equals	O
5.01	O
MB	O
.	O
</s>
<s>
on	O
the	O
D9090	O
;	O
153	O
Cylinders	O
×	O
6	O
Heads	B-Device
×	O
32	O
Sectors	O
×	O
256	O
Bytes/sector	O
equals	O
7.52	O
MB	O
.	O
</s>
<s>
3	O
×	O
ROMs	B-Device
(	O
Two	O
for	O
CBM	B-Device
DOS	I-Device
system	O
&	O
communication	O
with	O
host	O
computer	O
,	O
one	O
for	O
SASI	B-Architecture
communications	O
for	O
hard	B-Device
drive	I-Device
low	O
level	O
formatting	O
-	O
track	O
&	O
sector	O
layout	O
,	O
4	O
or	O
6	O
heads	B-Device
.	O
)	O
</s>
<s>
The	O
SASI	B-Architecture
interface	O
was	O
invented	O
by	O
Shugart	O
which	O
would	O
later	O
become	O
Seagate	O
.	O
</s>
<s>
SASI	B-Architecture
eventually	O
became	O
standardized	O
and	O
is	O
known	O
today	O
as	O
SCSI	B-Architecture
.	O
</s>
<s>
Capable	O
of	O
managing	O
2	O
x	O
MFM	B-Protocol
hard	B-Device
drive	I-Device
mechanisms	O
,	O
which	O
is	O
communicated	O
to	O
the	O
user	O
as	O
two	O
combined	O
directories	O
,	O
with	O
one	O
header	O
number	O
=	O
0	O
and	O
the	O
other	O
header	O
number	O
=	O
1	O
.	O
</s>
<s>
It	O
appears	O
the	O
DOS	O
was	O
never	O
fully	O
completed	O
by	O
Commodore	O
;	O
this	O
is	O
indicated	O
by	O
the	O
way	O
two	O
directories	O
overlap	O
for	O
the	O
one	O
device	O
and	O
the	O
number	O
of	O
blocks	O
free	O
is	O
displayed	O
as	O
if	O
only	O
one	O
hard	B-Device
drive	I-Device
is	O
in	O
use	O
.	O
</s>
<s>
The	O
DOS	O
will	O
also	O
"	O
lock	O
up	O
"	O
if	O
an	O
attempt	O
is	O
made	O
to	O
access	O
drive	O
unit	O
1	O
when	O
there	O
is	O
just	O
the	O
one	O
hard	B-Device
drive	I-Device
unit	O
connected	O
as	O
drive	O
unit	O
0	O
.	O
</s>
<s>
The	O
unit	O
uses	O
Tandon	O
TM602S/TM603S	O
hard	B-Device
disk	I-Device
drive	I-Device
units	O
.	O
</s>
<s>
Data	O
is	O
encoded	O
to	O
the	O
disk	O
platters	O
using	O
the	O
MFM	B-Protocol
disk	O
format	O
.	O
</s>
<s>
Internally	O
the	O
system	O
had	O
a	O
transfer	O
rate	O
of	O
5.0	O
Mbit/s	O
from	O
the	O
hard	B-Device
disk	I-Device
drive	I-Device
to	O
the	O
CBM	B-Device
DOS	I-Device
3.0	O
Controller	O
PCB	O
.	O
</s>
<s>
Any	O
4	O
or	O
6	O
head	O
MFM	B-Protocol
drive	O
mechanism	O
can	O
be	O
used	O
as	O
a	O
replacement	O
mechanism	O
.	O
</s>
<s>
Cylinders	O
=	O
153	O
(	O
per	O
hard	B-Device
disc	I-Device
)	O
6	O
head	O
drive	O
contains	O
3	O
platters	O
,	O
4	O
head	O
drive	O
contains	O
2	O
platters	O
.	O
</s>
<s>
Despite	O
the	O
small	O
storage	O
space	O
(	O
by	O
current	O
standards	O
)	O
of	O
these	O
legacy	O
hard	B-Device
drives	I-Device
,	O
formatting	O
either	O
can	O
require	O
a	O
fair	O
amount	O
of	O
patience	O
from	O
the	O
user	O
:	O
</s>
<s>
D9060	O
(	O
4	O
heads	B-Device
)	O
Formatting	O
takes	O
approximately	O
1	O
hour	O
.	O
</s>
<s>
D9090	O
(	O
6	O
heads	B-Device
)	O
Formatting	O
takes	O
approximately	O
1	O
hour	O
and	O
20	O
minutes	O
.	O
</s>
<s>
These	O
long	O
delays	O
can	O
be	O
attributed	O
by	O
the	O
overall	O
operation	O
which	O
consists	O
of	O
the	O
low-level	O
disk	O
format	O
by	O
the	O
SASI	B-Architecture
controller	O
,	O
followed	O
by	O
a	O
six-pass	O
test	O
pattern	O
write	O
to	O
the	O
whole	O
disk	O
surface	O
by	O
the	O
DOS	O
before	O
placing	O
the	O
initial	O
filing	O
system	O
information	O
.	O
</s>
<s>
With	O
minor	O
changes	O
to	O
the	O
CBM	B-Device
DOS	I-Device
ROM	B-Device
code	O
,	O
larger	O
capacity	O
hard	B-Device
disk	I-Device
drives	I-Device
could	O
be	O
swapped	O
into	O
the	O
D9060/D9090	O
unit	O
.	O
</s>
<s>
This	O
was	O
done	O
by	O
finding	O
drives	O
with	O
8	O
heads	B-Device
(	O
4	O
platters	O
)	O
and	O
256	O
cylinders	O
.	O
</s>
<s>
The	O
CBM	B-Device
DOS	I-Device
would	O
support	O
these	O
numbers	O
if	O
"	O
hard	O
coded	O
"	O
into	O
the	O
ROM	B-Device
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
an	O
Arizona	O
company	O
named	O
Copperstate	O
Cash	O
Register	O
was	O
selling	O
upgraded	O
units	O
to	O
the	O
business	O
and	O
BBS	B-Application
operator	O
community	O
.	O
</s>
<s>
256	O
Cylinders	O
×	O
8	O
Heads	B-Device
×	O
32	O
Sectors	O
×	O
256	O
Bytes/sector	O
equals	O
16.8	O
MB	O
.	O
</s>
<s>
These	O
hard	B-Device
drives	I-Device
can	O
be	O
daisy	B-Application
chained	I-Application
on	O
the	O
interface	O
with	O
each	O
device	O
using	O
a	O
different	O
device	O
number	O
.	O
</s>
<s>
The	O
D9060/D9090	O
were	O
designed	O
for	O
use	O
on	O
the	O
Commodore	O
CBM/PET	O
family	O
of	O
computers	O
,	O
but	O
because	O
these	O
metal-cased	O
family	O
of	O
computers	O
were	O
obsoleted	O
by	O
the	O
VIC-20	B-Device
and	O
the	O
Commodore	O
64	O
,	O
the	O
greatest	O
demand	O
for	O
these	O
drives	O
came	O
from	O
the	O
biggest	O
home	O
computer	O
user	O
market	O
in	O
the	O
world	O
at	O
the	O
time	O
,	O
the	O
VIC-20	B-Device
,	O
C64	O
and	O
C128	B-Device
users	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
several	O
companies	O
built	O
interfaces	O
that	O
effectively	O
give	O
a	O
VIC-20	B-Device
and	O
Commodore	O
64/128	O
an	O
IEEE-488	O
port	O
.	O
</s>
<s>
The	O
first	O
produced	O
was	O
the	O
VIC-20	B-Device
IEEE	O
488	O
cartridge	O
,	O
model	O
number	O
"	O
VIC-1112	O
"	O
,	O
produced	O
by	O
Commodore	O
.	O
</s>
<s>
The	O
original	O
Commodore	O
64/128	O
IEEE	O
Cartridge	O
was	O
produced	O
later	O
and	O
were	O
packaged	O
with	O
SFD-1001	B-Device
disk	O
drives	O
in	O
Europe	O
only	O
,	O
that	O
would	O
explain	O
why	O
this	O
unit	O
was	O
unknown	O
in	O
the	O
U.S.	O
</s>
<s>
It	O
uses	O
the	O
6502	B-General_Concept
CPU	I-General_Concept
,	O
6532	B-Device
RIOT	I-Device
,	O
6522	B-Device
VIA	I-Device
,	O
6850	O
ACIA	O
and	O
chips	O
.	O
</s>
<s>
MSD	O
VIE	O
(	O
"	O
VIC20	B-Device
-	O
488	O
"	O
)	O
-	O
6522	B-Device
VIA	I-Device
,	O
75160A	O
&	O
75161A	O
IEEE	O
drivers	O
.	O
</s>
<s>
MSD	O
CEI	O
(	O
"	O
C64	O
-	O
488	O
"	O
)	O
-	O
6526	B-Device
CIA	I-Device
,	O
75160A	O
&	O
75161A	O
IEEE	O
drivers	O
.	O
</s>
<s>
The	O
D9060	O
&	O
D9090	O
hard	B-Device
drives	I-Device
were	O
highly	O
sought	O
after	O
in	O
the	O
early	O
1980s	O
by	O
people	O
using	O
the	O
Commodore	O
64	O
and	O
Commodore	B-Device
128	I-Device
who	O
wanted	O
to	O
taste	O
the	O
luxury	O
of	O
having	O
all	O
their	O
utilities	B-Application
and	O
games	O
in	O
one	O
place	O
.	O
</s>
<s>
Files	O
and	O
games	O
loaded	O
faster	O
than	O
the	O
common	O
Commodore	B-Device
1541	I-Device
floppy	O
disk	O
drive	O
.	O
</s>
<s>
Many	O
bulletin	B-Application
board	I-Application
systems	I-Application
(	O
BBS	B-Application
)	O
were	O
set	O
up	O
using	O
these	O
hard	B-Device
drives	I-Device
as	O
they	O
could	O
access	O
information	O
quickly	O
and	O
could	O
hold	O
massively	O
more	O
information	O
compared	O
to	O
the	O
1541	O
disk	O
drive	O
which	O
could	O
only	O
access	O
on	O
one	O
side	O
of	O
a	O
floppy	O
disk	O
at	O
one	O
time	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
older	O
IEEE-488	O
disk	O
drives	O
and	O
hard	B-Device
drives	I-Device
were	O
being	O
acquired	O
by	O
large	O
numbers	O
of	O
C64	O
owners	O
to	O
connect	O
to	O
their	O
computer	O
using	O
an	O
IEEE-488	O
Interface	O
.	O
</s>
<s>
This	O
has	O
put	O
pressure	O
on	O
the	O
supply	O
of	O
these	O
devices	O
as	O
nowadays	O
they	O
are	O
wanted	O
by	O
both	O
Commodore	O
64/128	O
users	O
and	O
also	O
needed	O
by	O
people	O
using	O
the	O
PET	B-Device
family	I-Device
of	O
machines	O
,	O
that	O
these	O
drives	O
were	O
specifically	O
designed	O
for	O
.	O
</s>
