BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
192
Section 8: PCI Bus and HyperTransport Fabric
Document
1250_1125-UM100CB-R
PCI
AND
H
YPER
T
RANSPORT
A
DDRESS
R
ANGE
This section describes how devices on the PCI bus and HyperTransport fabric (and any buses bridged from
them) are mapped into the memory space. There are two complexities in the mapping. The first is supporting
the different types of access that need to be done, and the second is supporting endian swapping when the
part is running as a big endian system (both PCI and HyperTransport are little endian). A full discussion of the
endian issues is in
Section: “Endian Policies” on page 201
, the two endian options match bit lanes and match
byte lanes are defined there.
All the areas for mapping PCI and HyperTransport devices, except a HyperTransport only expansion area, are
put in the low 4 GBytes of the address space so they can be addressed using 32 bits of address in systems
that only use 32 bit addressing.
Accesses to the PCI and HyperTransport ranges of the address map should be done as uncacheable or
cacheable non-coherent. These addresses pass outside the coherence domain of the system. If cacheable
coherent accesses are made to the PCI or HyperTransport space the behavior of the system will become
UNDEFINED.