3-7
Themis Computer
3—Hardware Overview
Baseboard
3.1.12
Memory Subsystem
As seen in
Figure 3-3
, the USPII
e
-USB supports a single custom Themis Memory
Module, plugged directly into the Baseboard (see
Figure 3-4
on page 3-8). The
memory data path is 72 bits with 8 bits assigned to ECC. Memory complies to
PC-133 timing.
Figure 3-3.
Custom Memory Module Topology (Side View)
Memory capacities are offered in
128-MB
,
256-MB
,
512-MB
,
1-GB
,
2-GB
, and
4-GB
capacities (see
Table 2-2
on page 2-3). USPII
e
-USB memory design includes
Error Correction Code (ECC). A single bit error in a 64-bit word is corrected without
loss of a cycle.
In designing the memory subsystem, considerable attention was paid to minimizing
overall power consumption. The typical active power consumption of a
USPII
e
-USB with a 1-GB memory module is 23 watts (see
Table 2-9
on page 2-13
for other power requirements).
Baseboard
Custom Memory Module
Baseboard
Caution:
Because of the
VME Specification
requiring a 0.8-inch interboard sepa-
ration (see
Figure 1-1
on page 1-5) between VME slots, only one Memory Module
can be installed onto a USPII
e
-USB Baseboard (
stacking is not supported
).
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