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Chapter 2. Architecture and technical overview 27
Double the SMP support. Changes have been made in the fabric, L2 and L3 controller,
memory controller, GX controller, and processor RAS to provide support for the QCM that
allows the SMP system sizes to be double that which is available in POWER5 DCM-based
servers. However, current POWER5+ implementations only support single address loop.
Several enhancements have been made in the memory controller for improved
performance. The memory controller is ready to support DDR2 667 MHz DIMMs in the
future.
Enhanced redundancy in L1 cache, L2 cache, and L3 directory. Independent control of the
L2 cache and the L3 directory for redundancy to allow split-repair action has been added.
More word line redundancy has been added in the L1 Dcache. In addition, Array Built-In
Self Test (ABIST) column repair for the L2 cache and the L3 directory has been added.
2.2 Processor and cache
In the p5-520 and p5-520Q, the POWER5+ processors, associated L3 cache (if present), and
memory DIMMs are packaged on the system planar. The p5-520 1-core, 2-core, and
p5-520Q 4-core systems use different POWER5+ processor modules.
2.2.1 POWER5+ single-core module
The 1-core p5-520 POWER5+ system planar contains a single-core module (SCM) and the
local memory storage subsystem for that SCM. The POWER5+ single-core processor is
packaged in the SCM. The 1-core 1.65 GHz system planar contains a single-core module
(SCM) and the local memory storage subsystem for that SCM. L3 Cache is not available in
this configuration. Figure 2-3 on page 27 shows the layout of a 1.65 GHz p5-520 SCM and
associated memory.
Figure 2-3 p5-520 POWER5+ 1.65 SCM with DDR2 memory socket layout view
The 1-core 2.1 GHz p5-520 system planar contains a single-core module (SCM), the local
memory storage subsystem for that SCM, and the L3 Cache. Figure 2-4 shows the layout of a
2.1 GHz p5-520 SCM and associated memory.
Note: Because the POWER5+ processor modules are soldered directly to the system
planar, you must take special care in sizing and selecting the ideal CPU configuration.
POWER5+
core
1.9 MB Shared
L2 cache
L3
Ctrl
Mem
Ctrl
Single-Core Module
SCM
SMI-II SMI-II
1056 MHz
2 x 8 B for read
2 x 2 B for write
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
2 x 8 B
@528 MHz
GX+
Ctrl
Enhanced distributed switch
GX+
Bus
POWER5+
core
POWER5+
core
1.9 MB Shared
L2 cache
L3
Ctrl
Mem
Ctrl
Single-Core Module
SCM
SMI-II SMI-II
1056 MHz
2 x 8 B for read
2 x 2 B for write
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
DIMM
2 x 8 B
@528 MHz
GX+
Ctrl
Enhanced distributed switch
GX+
Bus