Chapter 1. zSeries 900 overview 7
Hiperspace services have been re-implemented to use real storage rather than expanded
storage. Although OS/390 Release 10 does not support expanded storage when running
under the new architecture, all of the Hiperspace APIs, as well as the Move Page (MVPG)
instruction, continue to operate in a compatible manner. There is no need to change products
that use Hiperspaces.
Up to 64 GB of memory
The z900 continues to employ storage size selection by Licensed Internal Code Configuration
Control introduced on the 9672 G5/G6 processors. Memory cards installed may have more
usable memory than required to fulfill the server order. LICCC will determine how much
memory is used from each card. Memory upgrades within the installed memory cards are
1.3.3 I/O connectivity
I/O cages
The z900 contains an I/O subsystem infrastructure which uses an I/O cage that provides 28
I/O slots, compared to the 9672 G5/G6 style cage with 22 slots. ESCON, FICON, FICON
Express (either in FICON or FCP modes), PCI Cryptographic Coprocessor (PCICC), PCI
Cryptographic Accelerator (PCICA), ISC links and OSA-Express cards plug into the zSeries
I/O cage - FC 2023. The z900 still supplies a Compatibility I/O cage - FC 2022, which has 22
slots, to accommodate parallel channels, OSA-2 (FDDI and Token Ring), and ESCON
four-port channel cards. ESCON four-port channel cards are used only in upgrading from a
9672 G5/G6 model. The I/O cards can be hot-plugged in the zSeries I/O cage. Installation of
an I/O cage remains a disruptive upgrade, so the Plan Ahead feature remains an important
consideration when ordering a z900 system.
The zSeries I/O cage takes advantage of an exclusive IBM packaging technology that
provides a subsystem with approximately seven times higher bandwidth than the previous
G5/G6 I/O cage. Each general purpose z900 model comes with one zSeries I/O cage
standard in the A-Frame (the A-Frame also contains the processor CEC cage). The zSeries
I/O cage, using new 16-port ESCON cards, can hold 256 ESCON channels; previous
packaging required three I/O cages to package the same number of channels. For FICON
and FICON Express, the zSeries I/O cage can accommodate up to 16 cards or 32 channels
per cage; with the previous technology, up to 36 channels would require three I/O cages.
Thus, much denser packaging and higher bandwidth has been achieved.
Both FC 2022 and FC 2023 cages are available on a z900. However, the I/O cage in the
A-frame will always be FC 2023. See Figure 1-4 on page 8 for details.
The Z-Frame is an optional I/O Frame and attaches to the A-Frame. The Z-Frame can contain
up to two of the new zSeries I/O cages, up to two compatibility I/O cages or a mixture of both.
Figure 1-4 shows the layout of the A- and Z-Frames and both types of I/O cages.

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