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GX Bus Options Expand Connectivity for POWER7 Servers

IBM Power Systems servers offer expanded connectivity through the use of GX bus technology. Several I/O drawer models as well as InfiniBand switch connectivity are supported through the GX bus connections.

GX Bus Types and I/O Drawers

The POWER7 servers feature two GX bus configurations: GX+ and GX++. GX+ buses operate at 5 Gbps (duplex), and GX++ buses operate at 20 Gbps (duplex).

Both PCI Express (PCIe) and PCI-eXtended (PCI-X) drawers can be connected to Power Systems through GX+/++ 12X adapter cards. The 12X I/O Drawer PCIe, SFF (#5802) drawer provides 10 PCIe Gen1 slots and 18 small form factor (SFF) disk bays. A similar drawer, the 12X I/O Drawer PCIe, no disk (#5877), provides 10 PCIe Gen1 slots without the disk bays. Finally, the PCI-X DDR 12X Expansion Drawer (#5796) provides six PCI-X slots in a 4U drawer that consumes half of a shelf. The #5796 drawer is generally installed in pairs, which provides 12 PCI-X slots in a 4U space.

When attached to an InfiniBand switch, GX+/++ adapters can deliver a high-speed communication path. Most InfiniBand switches operate at 4x speed and, therefore, it’s necessary to use a 12X to 4X channel-conversion cable when connecting a GX+/++ adapter to an InfiniBand switch. For Power Systems servers with low-profile Gen2 PCIe slots, another option is the 2-port, 4x InfiniBand adapter.

GX Bus Options by Server Model

Consider the following GX bus options for each POWER7 server model:

• Model 710 features one GX++ slot. Currently, GX adapter cards aren’t available for use with this model; however, the slot is provided for potential, future expansion.
• Model 720 has one GX++ slot. This can be populated with a Gen2 riser card or a GX++ 12x adapter. The Gen2 riser card adds four low-profile PCIe Gen2 slots to the server. If a GX++ 12X adapter card is installed, up to two #5802/#5877 12x PCIe expansion drawers or four #5796 I/O drawers can be installed per GX++ adapter.
• Model 730 includes two GX++ slots. Currently, you can configure a GX++ adapter for the first GX++ slot. The second GX++ slot is for potential, future expansion. One or two #5802/#5877 12x PCIe expansion drawers can be connected to the GX++ adapter.
• Model 740 provides two GX++ slots. The first one can be populated with a Gen2 riser card or a GX++ 12x adapter. The Gen2 riser card adds four low-profile PCIe Gen2 slots to the server. The second GX++ slot can be populated with a GX++ 12x adapter. If the second adapter card is installed, the number of available, full height PCIe adapter slots will be reduced from five to four. Each GX++ adapter card can support up to two #5802/#5877 12x PCIe expansion drawers or four #5796 I/O drawers.
• Model 750 features up to two GX slots: One GX+ and one GX++. When just one processor card is installed, a single GX+ adapter slot is available. If the second is installed, then the GX++ slot is also enabled. For each GX+/++ slot that’s populated with a 12X adapter, the number of available PCIe slots will be reduced by one. Each GX++ adapter card can support up to two #5802/#5877 12x PCIe expansion drawers or four #5796 I/O drawers.
• Model 755 has one GX++ slot. When populated with a GX++ 12X adapter, the ability to connect to InfiniBand switches is provided. I/O drawers are not supported on this model. Installation of the GX+ 12X adapter will reduce the number of available PCIe slots from three to two.
• Model 770/780 servers include two GX++ adapter slots per system enclosure. A fully configured system with four system enclosures provides the capability to install up to eight GX++ adapters. Each installed GX++ adapter card can support one or two #5802/#5877 12x PCIe expansion drawers or four #5796 I/O drawers. Installation of these adapters into Model 770/780 servers won’t reduce the number of available PCIe slots.
• Model 795 provides up to four GX++ hubs per processor book. A fully configured system with eight processor books enables you to install up to 32 GX++ hubs with support for up to 32 I/O drawers. Exclusive to the Model 795 are two 24-inch I/O drawer models. The first is the 12X I/O Drawer, SFF disk (#5803), which provides 20 Gen1 PCIe slots and 26 SFF disk bays. Also offered is the 12X I/O Drawer, no disk (#5873), which provides 20 PCIe Gen1 slots and no disk bays

Flexibility Through GX Bus Technology

GX++ bus technology is extremely fast and provides the option to connect a variety of I/O drawers and InfiniBand switches. This flexibility enables you to configure just the right amount of I/O expansion required for your server environment.

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