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22 p5-570 Technical Overview and Introduction
POWER5 chips extensively use a fine-grained, dynamic clock-gating mechanism. This
mechanism gates off clocks to a local clock buffer if dynamic power management logic knows
that the set of latches that are driven by the buffer will not be used in the next cycle. This
allows substantial power saving with no performance impact. In every cycle, the dynamic
power management logic determines whether a local clock buffer that drives a set of latches
can be clock-gated in the next cycle.
In addition to the switching power, leakage power has become a performance limiter. To
reduce leakage power, the POWER5 chip uses transistors with low threshold voltage only in
critical paths. The POWER5 chip also has a low-power mode, enabled when the system
software instructs the hardware to execute both threads at the lowest available priority. In low
power mode, instructions dispatch once every 32 cycles at most, further reducing switching
power. The POWER5 chip uses this mode only when there is no ready task to run on either
thread.
2.1.3 The POWER chip evolution
The p5-570 system complies with the RS/6000 platform architecture, which is an evolution of
the PowerPC Common Hardware Reference Platform (CHRP) specifications. Figure 2-3
shows the POWER chip evolution.
Figure 2-3 The POWER chip evolution
32bit
64bit
Note: Not all
processor speeds
available on all
models
POWER4
1.0 to 1.3
GHz
POWER4+
1.2 to 1.9 GHz
RS64-IV
600 / 750
pSeries p620, p660,
and p680
604e
332 /
375
p615, p630,
p650, p655, p670
and p690
Power3-II
333 / 375 /
450
Models 270, B80, and
POWER3 SP Nodes
RS64
125
S70
RS64-II
262.5
S7A
RS64-II
340
H70
RS64-III
450
F80, H80, M80, S80
Power3
200+
SP Nodes
+ SOI =
SOI
Copper =
F50
p630, p650, p655,
p670, and p690
1.2 to
1.9 GHz
Core
1.2 to
1.9 GHz
Core
Shared L2Shared L2
Distributed Switch
0.13 microns
2002-3
–Larger L2
–More LPARs
–High-speed Switch
POWER4+
Shared L2
Distributed Switch
0.18 microns
2001
POWER4™
–Distributed Switch
–Shared L2
–LPAR
–Autonomic computing
–Chip multiprocessing
1.0 to
1.3 GHz
Core
1.0 to
1.3 GHz
Core
Shared L2Shared L2
Distributed Switch
0.18 microns
2001
POWER4™
–Distributed Switch
–Shared L2
–LPAR
–Autonomic computing
–Chip multiprocessing
1.0 to
1.3 GHz
Core
1.0 to
1.3 GHz
Core
Shared L2
Distributed Switch
0.13 microns
2004
POWER5
TM
–Larger L2 and L3 caches
–Micro-partitioning
–Enhanced Distributed Switch
–Enhanced core parallelism
–Improved floating-point
–performance
–Faster memory environment
Mem Ctl
1.5 to
1.9 GHz
Core
1.5 to
1.9 GHz
Core
Shared L2Shared L2
Distributed Switch
0.13 microns
2004
POWER5
TM
–Larger L2 and L3 caches
–Micro-partitioning
–Enhanced Distributed Switch
–Enhanced core parallelism
–Improved floating-point
–performance
–Faster memory environment
Mem Ctl
1.5 to
1.9 GHz
Core
1.5 to
1.9 GHz
Core