Chapter 2. Architecture and technical overview 67
2.6 System bus
This section provides additional information related to the internal buses.
2.6.1 I/O buses and GX++ card
Each CEC enclosure of the Power 770 and Power 780 contains one POWER7+ processor
card. Each processor card comprises 3-core, 4-core, or 8-core single-chip module POWER7+
processors, with different frequencies depending on the configuration, such as 4.228Ghz,
3.724GHz, or 3.808Ghz
Within a CEC enclosure a total of two GX++ buses are available for I/O connectivity and
expansion. Each GX++ bus is routed through the midplane to the I/O backplane and drive to
two different POWER7+ processors. The two POWER7+ processors are responsible for the
other two IO chips, also routed through the midplane. Table 2-10 shows the I/O bandwidth for
available processors cards.
Table 2-10 External GX++ I/O bandwidth
2.6.2 Service processor bus
The flexible service processor (FSP) flex cable, which is located at the rear of the system, is
used for service processor (SP) communication between the system drawers. A SP card
(FC EU09) is installed in system drawer 1 and system drawer 2. The FSP/Clock
Pass-Through card (FC 5665 CCIN 2BBC) is installed in system drawers 3 and 4. These
cards connect to drawers 1 and 2 through the FSP flex cable. The FSP cable was changed to
point-to-point cabling similar to the processor drawer interconnect cable. When a system
drawer is added, another FSP flex cable is added. A detailed cable configuration is discussed
in 2.5, “CEC drawer interconnection cables” on page 60.
Processor card Slot description Frequency GX++ Bandwidth
(maximum theoretical)
4.228 GHz
3.808 GHz
4.424 GHz
3.7 GHz
CPU Socket 0 (CP0)
GX bus 1
2.464 GHz 19.712 GBps
CPU Socket 0 (CP0)
GX bus 0
2.464
GHz 19.712 GBps
Single enclosure (data portion is on average 2/3 total) 26.283 GBps
Total (4x enclosures) 157.696 GBps
Bandwidth: Technically, all the other interfaces, such as daughter card, asynchronous
port, DVD, USB, and the PCI Express slots are connected to two other internal GX++ ports
through two P7IOC chipsets. So, theoretically, if all the ports, devices, and PCIe slots are
considered, the total I/O bandwidth for a system with four CECs is 315.392 GBps.
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