IBM RS/6000 SP, Handbook

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RS/6000 SP and Clustered IBM
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pSeries Systems Handbook
2.2.2 System memory
The SP 375 MHz POWER3 SMP system supports 256 MB to 64 GB of 10 ns
SDRAM. System memory is controlled by the memory-I/O chip set through the
memory bus. The memory bus consists of a 512-bit data bus and operates at
62.5 MHz clock cycle., this bus is separated from the System bus (6xx bus),
which allows for concurrent operations on these two buses. For example,
cache-to-cache transfers can occur while a DMA operation is in progress to an
I/O device. There are memory card slots in the system. Each memory card
contains DIMM slots; 512 MB, 256 MB and 128 MB memory DIMMs are
supported. Memory DIMMs must be plugged in pairs and at least one memory
card with a minimum of 256 MB of memory must be plugged in for the system to
be operational. System memory is protected by Single Error Correction and
Double Error Detection ECC code.
2.2.3 I/O subsystem
The I/O subsystem is different in Wide, Thin, or High Nodes:
In 375 MHz POWER3 Wide or Thin Node, the memory-I/O controller chip set
implements a 64-bit plus parity, multiplexed address and data bus (6xx-MX bus)
for attaching up to three PCI bridge chips and the SP Switch MX2 Adapter. The
6xx-MX bus runs at 60 MHz concurrently and independently from the 6xx and
memory buses. At a 60 MHz clock cycle, the peak bandwidth of the 6xx-MX bus
is 480 MBps. The three PCI bridge chips attached to 6xx-MX bus provides the
interface up to 10 PCI slots: Two 32-bit PCI slots are in thin node and eight
additional 64-bit PCI slots are in wide node.
One of the PCI bridge chips (Bridge Chip0) provides support for integrated Ultra2
SCSI and 10Base2, 100BaseT Ethernet functions. The Ultra2 SCSI interface
supports up to four internal disks. An ISA bridge chip is also attached to PCI
Bridge Chip0 for supporting two serial ports and other internally used functions in
the 375 Mhz POWER3 SMP node.
The I/O subsystem in the 375 MHz POWER3 High Node has five PCI slots via
the PCI bridges (MX-PCI), which have the RIO-MX and I/O hub as an additional
interface.
The I/O hub can also drive up to six SP Expansion I/O units (RIO). Each RIO
have eight PCI slots. Figure 2-3 on page 31 shows the rear view of POWER3
High Node and five SP Expansion I/O Units connections.