<s>
The	O
MSD	B-Device
Super	I-Device
Disk	I-Device
were	O
a	O
series	O
of	O
5¼-inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
compatible	O
to	O
some	O
degree	O
with	O
the	O
Commodore	B-Device
1541	I-Device
disk	O
drive	O
.	O
</s>
<s>
Two	O
different	O
versions	O
of	O
the	O
MSD	B-Device
Super	I-Device
Disk	I-Device
were	O
available	O
:	O
the	O
single-drive	O
model	O
,	O
SD-1	O
;	O
and	O
the	O
dual-drive	O
model	O
,	O
SD-2	O
.	O
</s>
<s>
Introduced	O
in	O
1983	O
,	O
the	O
MSD	B-Device
Super	I-Device
Disk	I-Device
drives	O
were	O
the	O
first	O
third-party	O
devices	O
designed	O
for	O
compatibility	O
with	O
the	O
Commodore	O
64	O
,	O
although	O
other	O
manufacturers	O
soon	O
followed	O
suit	O
.	O
</s>
<s>
The	O
MSD	O
drives	O
include	O
both	O
an	O
IEEE-488	O
parallel	B-Device
interface	I-Device
and	O
the	O
custom	O
Commodore	O
serial	B-Protocol
interface	I-Protocol
.	O
</s>
<s>
Therefore	O
,	O
they	O
can	O
be	O
connected	O
to	O
any	O
Commodore	O
8-bit	O
system	O
,	O
from	O
the	O
Commodore	B-Device
PET	I-Device
to	O
the	O
C64	O
and	O
C128	B-Device
,	O
without	O
any	O
converters	O
or	O
other	O
add-on	O
devices	O
.	O
</s>
<s>
The	O
MSD	B-Device
SD-1	I-Device
was	O
more	O
expensive	O
than	O
the	O
Commodore	B-Device
1541	I-Device
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
typical	O
mail-order	O
advertisement	O
in	O
the	O
January	O
1985	O
issue	O
of	O
RUN	O
Magazine	O
lists	O
the	O
MSD	B-Device
SD-1	I-Device
single	O
drive	O
at	O
$249.95	O
,	O
compared	O
to	O
$199.95	O
for	O
the	O
Commodore	B-Device
1541	I-Device
.	O
</s>
<s>
The	O
SD-2	O
was	O
listed	O
at	O
$449.95	O
,	O
much	O
less	O
than	O
the	O
comparable	O
Commodore	B-Device
PET	I-Device
dual	O
drive	O
(	O
CBM	B-Device
4040	I-Device
)	O
which	O
sold	O
for	O
$699	O
.	O
</s>
<s>
To	O
justify	O
the	O
typically	O
$50	O
or	O
so	O
(	O
)	O
higher	O
price	O
ca.January	O
1985	O
of	O
the	O
MSD	B-Device
SD-1	I-Device
single	O
drive	O
vis-à-vis	O
the	O
1541	O
,	O
however	O
,	O
MSD	O
offered	O
several	O
advantages	O
over	O
the	O
1541	O
.	O
</s>
<s>
In	O
an	O
August	O
1985	O
review	O
of	O
1541	O
replacements	O
,	O
RUN	O
Magazine	O
wrote	O
that	O
the	O
MSD	B-Device
SD-2	I-Device
was	O
"	O
built	O
like	O
a	O
tank	O
and	O
can	O
run	O
24	O
hours	O
a	O
day	O
for	O
weeks	O
"	O
.	O
</s>
<s>
And	O
while	O
program	O
loading	O
and	O
saving	O
was	O
no	O
faster	O
than	O
on	O
the	O
1541	O
when	O
using	O
the	O
serial	B-Protocol
interface	I-Protocol
due	O
to	O
that	O
interface	O
's	O
limitations	O
,	O
both	O
the	O
SD-1	O
and	O
SD-2	O
were	O
several	O
times	O
faster	O
when	O
connected	O
to	O
the	O
computer	O
via	O
the	O
IEEE-488	O
interface	O
.	O
</s>
<s>
Furthermore	O
,	O
a	O
blank	O
disk	O
could	O
be	O
formatted	O
in	O
only	O
18	O
seconds	O
on	O
the	O
MSD	B-Device
Super	I-Device
Disk	I-Device
series	O
,	O
compared	O
to	O
1	O
minute	O
and	O
22	O
seconds	O
on	O
the	O
1541	O
.	O
</s>
<s>
The	O
MSD	B-Device
SD-2	I-Device
implements	O
the	O
Commodore	B-Device
DOS	I-Device
Duplicate	O
command	O
from	O
the	O
older	O
Commodore	B-Device
PET	I-Device
dual	O
drive	O
series	O
.	O
</s>
<s>
The	O
Commodore	O
BASIC	O
V4.0	O
COPY	O
command	O
can	O
also	O
be	O
used	O
to	O
copy	O
files	O
from	O
one	O
drive	O
to	O
another	O
on	O
the	O
MSD	B-Device
SD-2	I-Device
,	O
a	O
feature	O
not	O
available	O
with	O
two	O
1541	O
drives	O
.	O
</s>
<s>
However	O
,	O
the	O
MSD	B-Device
Super	I-Device
Disk	I-Device
drives	O
have	O
difficulty	O
loading	O
most	O
copy-protected	O
software	O
,	O
due	O
to	O
substantial	O
differences	O
in	O
the	O
DOS	O
code	O
,	O
memory	O
mapping	O
and	O
the	O
microcontroller	B-Architecture
used	O
.	O
</s>
<s>
Internally	O
,	O
both	O
models	O
feature	O
TEC	O
brand	O
(	O
model	O
FB-501	O
)	O
floppy	B-Device
drive	I-Device
mechanisms	O
.	O
</s>
<s>
The	O
electronics	O
on	O
the	O
mechanisms	O
are	O
modified	O
by	O
MSD	O
to	O
be	O
compatible	O
with	O
the	O
GCR	B-Device
recording	O
format	O
used	O
by	O
all	O
Commodore	O
floppy	B-Device
disk	I-Device
drives	I-Device
at	O
that	O
time	O
(	O
the	O
D9060/90	B-Device
hard	O
disks	O
and	O
the	O
later	O
produced	O
1581	O
3½-inch	O
drive	O
used	O
the	O
MFM	B-Protocol
recording	O
format	O
)	O
.	O
</s>
<s>
The	O
main	O
control	O
board	O
utilizes	O
a	O
1MHz	O
Rockwell	O
International	O
6511Q	O
microcontroller	B-Architecture
.	O
</s>
<s>
The	O
time	O
savings	O
alone	O
,	O
when	O
backing	O
up	O
disk	O
files	O
,	O
will	O
rapidly	O
pay	O
for	O
the	O
machine	O
"	O
,	O
and	O
also	O
a	O
good	O
replacement	O
for	O
the	O
CBM	B-Device
4040	I-Device
.	O
</s>
