Chapter 1
Overview
PCI-X I/O
14
PCI-X I/O
The new PCI-X I/O chassis holds PCI and PCI-X type I/O cards for the two new systems. Older Superdome
systems used only the PCI cards and card cages. The chassis consists of the following three printed circuit
assemblies:
PCI-X I/O Backplane
PCI-X I/O Power Board
PCI-X I/O Transfer Board
It also contains the necessary mechanical components required to support 12 PCI-X card slots. The I/O
system architecture is shown in Figure 1-8. This figure depicts the path between the system I/O backplane
and the PCX-X card slots. The CC on each cell board communicates with the System Bus Adaptor (SBA) on
the PCI-X card cage over the SBA link. The SBA link consists of both an inbound and an outbound link with
an effective bandwidth of approximately 1 GB/sec. in each direction. The SBA converts the SBA link protocol
into enhanced “ropes.” The SBA can support up to 16 of these high-speed bidirectional enhanced rope links for
a total aggregate bandwidth of approximately 8 GB/sec. The Local Bus Adaptors (LBA) is connected to the I/O
by either a single or dual enhanced ropes.
PCI-X Backplane
The heart of the PCI-X I/O card cage backplane is SBA ASIC plus 12 LBA ASICs (one per PCI-X slot). The
SBA communicates directly with the CC of the host cell board by way of a high bandwidth SBA link. The SBA
spawns 16 enhanced ropes that communicate with the LBA chips. Each LBA, then, produces a single 64-bit
PCI-X bus, which supports a single PCI/PCI-X card.
The 16 enhanced ropes generated by the SBA are routed to the 12 LBAs chips. All PCI-X card slots can
support PCI-X 133. Each slot is keyed for 3.3-volt signaling and can accept any universal or 3.3-Volt only PCI
or PCI-X add-in card.
Associated with each PCI-X slot is a hot swap controller, which enables the online addition, replacement, and
deletion of individual PCI-X cards without disturbing the operation of other cards in the system. The LBA
provides the control/status signals and internal registers necessary for firmware to control and monitor the
power status of a PCI-X slot. It also provides firmware control of the Attention indicator LED. The Slot State
indicator LED is driven directly by the hot swap controller.
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