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10 RS/6000 7025 Model F80 Technical Overview
Internal I/O Architecture
As already discussed, the system includes one I/O host bridge chip managing all
the I/O between the I/O adapters and the memory controller using RIO
connections. On the other side, the I/O host bridge provides two primary PCI
busses, operating at 66 MHz and 64-bit wide.
The service processor and a PCI-to-PCI bridge chip are connected to the first
primary PCI bus. The PCI-to-PCI bridge provides three 64-bit hot-plug PCI slots
and the onboard dual SCSI adapter (F/W SCSI internal, Ultra2 SCSI external). A
PCI-to-ISA bridge chip is connected to the service processor providing an ISA
bus. The ISA bus is used by the National Super I/O chip providing the floppy drive
controller, two of the four serial ports, keyboard and mouse ports, and the parallel
printer interface. A 16552 DUART chip is also connected to the service processor
providing the other two serial ports.
The second bus is connected to another two PCI bridges, which provide another
seven 64-bit hot-plug PCI slots. The onboard 10/100 Mb/s Ethernet adapter is
connected to this chip.
Each slot represents a separate PCI bus, which simplifies the hot-plug
functionality. Figure 7 shows the design of the I/O architecture.
Figure 7. Internal Architecture of Model F80
PCI Slots
All PCI slots are PCI 2.2 compliant and are hot-plug enabled, which allows most
PCI adapters to be removed, added, or replaced without powering down the
system. This function enhances system availability and serviceability.
Six 64-bit slots operate at 3.3V signaling at 66 MHz, in contrast to the four 64-bit
slots which operate at 5V signaling at 50 MHz (see Figure 7). When adding
adapters to the system, it is important which signaling the adapter works: 3.3V,
5V, or universal, which means the adapter works at both voltages. That is, for
example, the reason why a PCI 3-Channel Ultra2 SCSI RAID Adapter (# 2494)
can be placed only in slots 6, 7, 11, or 12. Refer to the
PCI Adapter Placement
Reference Guide
, SA38-0538 for further information.