6947ch02.fm Draft Document for Review April 7, 2004 6:15 pm
34 IBM eServer zSeries 990 Technical Guide

A frame

As shown in Figure 2-9, the main components in the A-frame are:
1. Two Internal Battery Features (IBFs)
The optional Internal Battery Feature provides the function of a local uninterrupted power
source.
The IBF further enhances the robustness of the power design, increasing Power Line
Disturbance immunity. It provides battery power to preserve processor data in case of a
loss of power on both of the AC feeders from the utility company. The IBF can hold power
briefly over a “brownout”, or for orderly shutdown in case of a longer outage. The IBF
provides up to 20 minutes of full power, depending on I/O configuration.
2. One or two Modular Refrigeration Units (MRUs) that are air-cooled by their own internal
cooling fans.
3. The CEC cage, containing up to four books, each with two insulated refrigeration lines to
an MRU.
4. I/O Cage 1, which can house all supported types of channel cards. An I/O cage
accommodates up to 420 ESCON channels or up to 40 channels in the absence of any
other card.
5. Air-moving devices (AMD) providing N+1 cooling for the MBAs, memory, and DCAs.

Z frame

As shown in Figure 2-9, the main components in the Z-frame are:
1. Two Internal Battery Features (IBFs) (see IBF in A frame for more information).
2. The Bulk Power Assemblies (BPAs).
3. I/O cage 2 (bottom), and I/O cage 3 (top).Note that both I/O cages are the same as the
one in the A frame, and can house all supported types of channel card.
The Z frame holds: no cages; only the bottom cage (I/O cage 2); or both the bottom and
top I/O cages (I/O cage 2 and I/O cage 3).
4. The Service Element (SE) tray, which is located in front of I/O cage 2, contains the two
SEs.
I/O cages
There are 12 STI buses per book to transfer data, with a bi-directional bandwidth of
2.0 GB/sec each. An STI is driven off an MBA. There are three MBAs per book, each driving
four STIs, providing an aggregated bandwidth of 24 GB/sec per book.
The STIs connect to I/O cages that may contain a variety of channel, coupling link,
OSA-Express and Cryptographic feature cards:
򐂰ESCON channels (16 port cards).
򐂰FICON channels (FICON or FCP modes, 2 port cards).
򐂰ISC-3 links (up to 4 coupling links, two links per daughter card (ISC-D). Two daughter
cards plug into one mother card (ISC-M).
򐂰Integrated Cluster Bus (ICB) channels, both ICB-2 (333 MB/sec) and ICB-3 (1 GB/sec).
Both ICB-2 and ICB-3 (compatibility mode ICBs) require an STI extender card in the I/O
cage.
򐂰OSA-Express channels
– OSA-E Gb Ethernet
– Fast Ethernet