Chapter 2. Architecture and technical overview
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2.2.10 Comparison of the POWER7, , and POWER8 processors
Table 2-4 shows comparable characteristics between the generations of POWER7,
, and POWER8 processors.
Table 2-4 Comparison of technologies for the POWER8 processor and the prior generations
2.3 Memory subsystem
The Power E870 can have up to two system nodes per system with each system node having
32 DDR3 CDIMM slots capable of supporting 16 GB, 32 GB, and 64 GB CDIMMs running at
speeds of 1600 MHz. This allows for a maximum system memory of 4 TB for the
64 DDR3 CDIMMs slots in a system comprised of two system nodes.
The Power E880 can have up to four system nodes per system with each system node having
32 DDR3 CDIMM slots capable of supporting 16 GB, 32 GB, 64 GB, and 128 GB CDIMMs
running at speeds of 1600 MHz. This allows for a maximum system memory of 16 TB for the
128 DDR3 CDIMMs slots of a system comprised of four system nodes.
The memory on the systems are Capacity Upgrade on Demand capable, allowing for the
purchase of additional memory capacity and dynamically activate it when needed. It is
required that at least 50% of the installed RAM capacity is active.
The Power E870 and E880 servers support an optional feature called Active Memory
Expansion. This allows the effective maximum memory capacity to be much larger than the
true physical memory. This feature runs innovative compression and decompression of
memory content by using a dedicated coprocessor present on each POWER8 processor to
Characteristics
POWER7
POWER8
Technology
45 nm
32 nm
22 nm
Die size
567 mm
2
567 mm
2
649 mm
2
Number of transistors
1.2 billion
2.1 billion
4.2 billion
Maximum cores
8
8
12
Maximum SMT
threads per core
4 threads
4 threads
8 threads
Maximum frequency
4.25 GHz
4.4 GHz
4.35 GHz
L2 Cache
256 KB per core
256 KB per core
512 KB per core
L3 Cache
4 MB or 8 MB of
FLR-L3 cache per core
with each core having
access to the full 32
MB of L3 cache,
on-chip eDRAM
10 MB of FLR-L3
cache per core with
each core having
access to the full 80
MB of L3 cache,
on-chip eDRAM
8 MB of FLR-L3 cache
per core with each
core having access to
the full 96 MB of L3
cache, on-chip
eDRAM
Memory support
DDR3
DDR3
DDR3 and DDR4
I/O bus
GX++
GX++
PCIe Gen3
Note: At the time of writing, the Power E880 supports only two system nodes per server.
This allows for a maximum of 8 TB of memory for the 64 DDR3 CDIMM slots.
