AT&T 3B2/300 Technical Reference Manual page 150

EQUIPMENT D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - -
CM523A 4-Megabyte RAM Card
The CM523A 4-Megabyte RAM Card uses surface mount technology. The card is a double-sided
(components on both sides) multilayer board containing 176 surface mounted 256K by 1-bit DRAM
chips [including 48 chips for storing Error Correction Code (ECC) information] and 9 surface mount
memory drivers. Seventy-six bypass capacitors are mounted near the DRAM and memory drivers. The
CM523A Card can be used in all models of Version 3 3B2 computers. Connection to the system board
is via a 120-pin connector on the backplane. Card pinout information is provided in Appendix B. The
card is 6.5 inches wide by 7.4 inches deep. Figure 2-33 shows the component layout of the CM523A
Card.
1\
7.4"
v
v
0.75"
I\
2
DD
DDDDDDD
DDDDDD
120
DD D
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
DDDDDDDD
0 DDDDDDDD
0
l o
Conventional Component Side (Top)
(Bottom Side also has Memory Chips)
CJ
CJ
ol
Figure 2-33: CM523A 4-Megabyte, Surface Mounted, RAM Card Layout
2-126 TECHNICAL REFERENCE MANUAL