IBM DS8800, Introduction And Planning Manual, Page: 30 / 256

The EPLD is an optional feature that temporarily maintains power for the entire
subsystem for up to 50 seconds to minimize the impact of the power line
disturbance. This feature is highly recommended for areas where power source is
not reliable This feature adds two separate pieces of hardware to the DS8000:
v
For each PPS in each model, a booster module is added. When the BBUs supply
power to the primary power bus, battery power is fed into the booster module,
which in turn keeps disk enclosure power present.
v
Batteries will be added to expansion models that do not already have them. The
base model and the first expansion model will already have BBUs but
subsequent expansion models will not include BBUs until the EPLD feature is
installed.
With the addition of this hardware, the DS8000 will be able to run for
approximately 50 seconds on battery power before the processor enclosures
begin to copy NVS data to internal disk and then shut down. This allows for up
to a 50-second interruption to line power with no outage to the DS8000.
Model 95E (expansion model)
Figure 5 on page 9 shows the expansion model configuration of a Model 95E and
the increased number of storage enclosures
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that can be added.
The back side of the expansion model is the model power area. The expansion
models do not contain rack power control cards; these cards are only present in the
base model.
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4
1
2
3
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Figure 4. Base model (front and back views) of a Model 951 (4-way)
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Introduction and Planning Guide