Operator`s manual

APPENDIX E. CHANGING RAM OR PROM CHIPS
E-2
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 software PROMS, five 8K
RAM chips (CSI Model number EMX8) should
also be installed.
The older 21X has jumpers at locations M15,
W20, and W27 (Figure E-1). With 8K RAM
chips installed, M15 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 all good RAM.
E.3 CHANGING PROM CHIPS
PROMs are installed at locations 6, 7, and 8 in
Figure E-1. 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 8 and the PROM
with the highest number in socket 6, but check
the documentation received with the PROM
update to be sure.
After changing 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 for the PROMS.