IBM 990 Reference Manual page 8

To support the new scalability of the z990 a new improve-
ment to the I/O Subsystem has been introduced to "break
the barrier" of 256 channels per Central Electronic Com-
plex (CEC). This provides "horizontal" growth by allowing
the defi nition of up to four Logical Channel SubSystems
each capable of supporting up to 256 channels giving a
total of up to 1024 CHPIDs per CEC. The increased scal-
ability is further supported by the increase in the number
of Logical Partitions available from the current 15 LPARs to
a new 30 LPARs. There is still a 256-channel limit per oper-
ating system image.
These are some of the signifi cant enhancements in the
zSeries 990 server that bring improved performance, avail-
ability and function to the platform. The following sections
highlight the functions and features of the server.
z990 Design and Technology
The z990 is designed to provide balanced system perfor-
mance. From processor storage to the system's I/O and
network channels, end-to-end bandwidth is provided and
designed to deliver data where and when it is needed.
The z990 provides a signifi cant increase in system scal-
ability and opportunity for server consolidation by pro-
viding four models, from one to four MultiChip Modules
(MCMs), delivering up to a maximum 32-way confi gura-
tion. The MCMs are confi gured in a book package, with
each book comprised of a MultiChip Module (MCM),
memory cards and Self-Timed Interconnects. The MCM,
which measures approximately 93 x 93 millimeters (42%
smaller than the z900), contains the processor unit (PU)
chips, the cache structure chips and the processor stor-
age controller chips. The MCM contains 101 glass ceramic
layers to provide interconnection between the chips and
the off-module environment. In total, there is approximately
0.4 kilometer of internal copper wiring on this module.
This new MCM packaging delivers an MCM 42% smaller
than the z900, with 23% more I/O connections and 133%
I/O density improvement. Each MCM provides support for
12 PUs and 32 MB level 2 cache. Each PU contains 122
million transistors and measures 14.1 mm x 18.9 mm. The
design of the MCM technology on the z990 provides the
fl exibility to confi gure the PUs for different uses; two of
the PUs are reserved for use as System Assist Processors
(SAPs), two are reserved as spares. The remaining inac-
tive 8 PUs on the MCM are available to be characterized
as either CPs, ICF processors for Coupling Facility appli-
cations, IFLs for Linux applications, IBM ^ zSeries
Application Assist Processor (zAAPs) for Java applications
or as optional SAPs, providing the customer with tremen-
dous fl exibility in establishing the best system for running
applications. Each model of the z990 must always be
ordered with at least one CP, IFL or ICF.
The PU, which uses the latest chip technology from IBM
semiconductor laboratories, is built on CMOS 9S-SOI with
copper interconnections. The 14.1 mm x 18.9 mm chip has
a cycle time of 0.83 nanoseconds. Implemented on this
chip is the z/Architecture with its 64-bit capabilities includ-
ing instructions, 64-bit General Purpose Registers and
translation facilities.
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