System Bus; I/O Buses And Gx++ Card; Service Processor Bus - IBM Power 780 Technical Overview And Introduction

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
Processor card
4.228 GHz
3.808 GHz
4.424 GHz
3.7 GHz
Single enclosure (data portion is on average 2/3 total)
Total (4x enclosures)
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.

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.
Slot description Frequency
CPU Socket 0 (CP0) 2.464
GX bus 1
CPU Socket 0 (CP0) 2.464
GX bus 0
Chapter 2. Architecture and technical overview
GX++ Bandwidth
(maximum theoretical)
GHz
19.712 GBps
GHz
19.712 GBps
26.283 GBps
157.696 GBps
67