<s>
The	O
Metrovick	B-Device
950	I-Device
was	O
a	O
transistorized	B-Device
computer	I-Device
,	O
built	O
from	O
1956	O
onwards	O
by	O
British	O
company	O
Metropolitan-Vickers	O
,	O
to	O
the	O
extent	O
of	O
six	O
or	O
seven	O
machines	O
,	O
which	O
were	O
"	O
used	O
commercially	O
within	O
the	O
company	O
"	O
or	O
"	O
mainly	O
for	O
internal	O
use	O
"	O
.	O
</s>
<s>
In	O
November	O
1953	O
Richard	O
Grimsdale	O
and	O
Douglas	O
Webb	O
of	O
Manchester	O
University	O
first	O
demonstrated	O
their	O
prototype	O
transistorized	B-Device
computer	I-Device
using	O
92	O
point-contact	O
transistors	O
and	O
550	O
diodes	O
in	O
order	O
to	O
test	O
the	O
suitability	O
of	O
transistors	O
in	O
improving	O
the	O
reliability	O
of	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
computer	O
.	O
</s>
<s>
This	O
machine	O
was	O
similar	O
to	O
the	O
Mark	O
I	O
,	O
except	O
that	O
it	O
did	O
not	O
include	O
Williams	B-General_Concept
tubes	I-General_Concept
and	O
used	O
only	O
the	O
magnetic	B-General_Concept
drum	I-General_Concept
for	O
main	O
memory	O
.	O
</s>
<s>
The	O
only	O
storage	O
used	O
was	O
a	O
drum	B-General_Concept
(	O
reused	O
from	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
)	O
.	O
</s>
<s>
This	O
meant	O
that	O
the	O
average	O
random	B-General_Concept
access	I-General_Concept
time	O
to	O
a	O
word	O
in	O
store	O
was	O
half	O
a	O
drum	B-General_Concept
revolution	O
,	O
i.e.	O
,	O
with	O
64	O
words	O
on	O
a	O
track	O
,	O
32	O
times	O
the	O
random	B-General_Concept
access	I-General_Concept
time	O
for	O
a	O
word	O
if	O
it	O
could	O
be	O
stored	O
in	O
a	O
true	O
RAM	B-Architecture
.	O
</s>
<s>
In	O
comparison	O
,	O
the	O
Mark	O
1	O
had	O
also	O
included	O
a	O
number	O
of	O
Williams	B-General_Concept
tubes	I-General_Concept
to	O
provide	O
computer	O
registers	O
and	O
dramatically	O
speed	O
access	O
to	O
a	O
small	O
amount	O
of	O
data	O
;	O
thus	O
the	O
Transistor	B-Device
Computer	I-Device
was	O
slower	O
than	O
the	O
Mark	O
1	O
.	O
</s>
<s>
The	O
drum	B-General_Concept
was	O
even	O
used	O
to	O
store	O
the	O
Accumulator	B-General_Concept
and	O
the	O
Current	O
Instruction	O
.	O
</s>
<s>
By	O
1955	O
the	O
design	O
was	O
re-built	O
with	O
a	O
Mark	O
I-style	O
B-line	O
accumulator/index	O
register	O
and	O
hardware	O
multiplier	O
.	O
</s>
<s>
The	O
new	O
model	O
could	O
add	O
two	O
44-bit	O
numbers	O
in	O
1.5	O
drum	B-General_Concept
revolutions	O
,	O
which	O
,	O
at	O
a	O
drum	B-General_Concept
spin	O
rate	O
of	O
3000	O
RPM	O
,	O
amounted	O
to	O
roughly	O
30	O
milliseconds	O
per	O
addition	O
.	O
</s>
<s>
Although	O
faster	O
than	O
the	O
Mark	O
I	O
internally	O
,	O
the	O
lack	O
of	O
Williams	B-General_Concept
tubes	I-General_Concept
made	O
it	O
run	O
much	O
more	O
slowly	O
;	O
the	O
Mark	O
I	O
could	O
add	O
two	O
40-bit	O
numbers	O
in	O
1.8	O
milliseconds	O
.	O
</s>
<s>
A	O
third	O
"	O
regenerative	O
"	O
drum	B-General_Concept
track	O
formed	O
an	O
8-word	O
B	O
store	O
.	O
</s>
<s>
The	O
instruction	O
times	O
were	O
directly	O
related	O
to	O
the	O
30-millisecond	O
drum	B-General_Concept
revolution	O
time	O
(	O
the	O
basic	O
unit	O
being	O
the	O
time	O
to	O
read	O
a	O
word	O
,	O
i.e.	O
</s>
<s>
They	O
adopted	O
the	O
design	O
of	O
the	O
1955	O
Manchester	O
University	O
transistor	B-Device
computer	I-Device
as	O
the	O
Metrovick	B-Device
950	I-Device
.	O
</s>
<s>
The	O
only	O
relevant	O
experience	O
in	O
Metropolitan-Vickers	O
was	O
that	O
in	O
the	O
early	O
1930s	O
they	O
had	O
manufactured	O
a	O
mechanical	O
calculating	O
machine	O
in	O
the	O
form	O
of	O
the	O
differential	B-Device
analyser	I-Device
in	O
conjunction	O
with	O
Douglas	O
Hartree	O
of	O
Manchester	O
University	O
.	O
</s>
<s>
The	O
production	O
version	O
was	O
known	O
as	O
the	O
Metrovick	B-Device
950	I-Device
and	O
was	O
built	O
from	O
1956	O
to	O
the	O
extent	O
of	O
six	O
or	O
seven	O
machines	O
,	O
which	O
were	O
"	O
used	O
commercially	O
within	O
the	O
company	O
"	O
or	O
"	O
mainly	O
for	O
internal	O
use	O
"	O
.	O
</s>
