C-18 Sun Blade 1500 Service, Diagnostics, and Troubleshooting Manual • December 2004
C.4.3.3 PCI I/O Cache
Each PCI leaf has an I/O cache. Each PCI I/O cache has eight entries, each of which
contains 64 bytes of data. The I/O cache can also perform data prefetching, to
minimize DMA read latency.
C.4.3.4 PCI-ISA Bridge
The ISA bus is an I/O bus that runs at 8MHz. The Sun Blade 1500 workstation uses
only a subset of this bus called the XBus.
C.4.3.5 PCI Configuration and I/O Space
The PCI configuration and I/O space in UltraSPARC IIIi based systems conforms to
the PCI Local Bus Specification Revision 2.2 and are partitioned through a
software/firmware convention. 32 MB of space is reserved for each PCI bus in the
system:
■ 16 MB (lower) for the PCI configuration space
■ 16 MB (upper) for the PCI I/O space
The PCI specification defines the configuration space for software initialization and
configuration of PCI devices. This space is limited to a maximum size of 16 MB per
device. Accesses in this space generate PCI transactions called “Configuration
Cycles” which are decoded by the JIO.
The PCI specification also defines a 32-bit I/O space for each device. The I/O space
is accessed through dedicated transactions and is provided so as to support devices
that are “noncompliant”.
C.4.4 M1535D+
The Sun Blade 1500 workstation uses the M1535D+ I/O subsystem from Acer Labs.
The M1535D+ is a highly integrated system I/O chipset in a 328-pin BGA package.
The M1535D+ interfaces the PCI A bus and the following interfaces:
■ USB 1.1
■ ATA 100
■ SMBus
■ XBus
■ Parallel
■ Serial
■ AC97
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