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APPENDIX
E.
CHANGING RAM OR PROM CHIPS
The earliest 21Xs
were shipped with only two
4K RAM
chips. Current
software
does not
check for
this condition;
if
an old
21X is being
upgraded
to new sottware PROMS, five 8K
RAM
chips (CSl Modelnumber
EMXS)
should
also
be installed.
The
older 21X has iumpers at locations M15,
W2O,
and W27 (Figure
E-l).
With
8K RAM
chips
installed,
Ml5
should
be
jumpered
on
the
right
set of pins and W20 and W27 should be
jumpered
on
the left set of
Pins.
After
changing RAM chips reassemble the 21X,
turn
on
the power and confirm that the power-up
check
shows
allgood
RAM.
E.3
CHANGING PROM CHIPS
PROMs are installed
at locations 6, 7, and 8
in
Figure
E-l.
The procedure for changing a
PROM
is
the same as for a RAM chip, carefully
pry
out
the old chip and insert the new one,
being certain that
the notch on the chip
is
toward
the close edge
of
the
card and that
all
pins are
correctly seated
in
the sockets.
In
general,
the PROM chip with the lowest
number is
inserted in socket
I
and
the PROM
with
the highest number in socket 6, but check
the documentation received with the PROM
update
to be sure.
Afterchanging PROMS, reassemble the 21X
and
turn
on
the
power.
Confirm that
the power-
up
check indicates that all PROMS and RAM
are
good. Then
check
the signature
in
the *B
Mode
to
be
certain that
they match those sent
with
the documentation
forthe
PROMS.
E-2
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