Processor Configuration Registers
40
Datasheet, Volume 2
2.3.13.2
PCI Express* Interface Decode Rules
All “SNOOP semantic” PCI Express transactions are kept coherent with processor
caches.
All “Snoop not required semantic” cycles must reference the direct DRAM address
range. PCI-Express non-snoop initiated cycles are not snooped.
If a “Snoop not required semantic” cycle is outside of the address range mapped to
system memory, then it will proceed as follows:
• Reads: Sent to DRAM address 000C_0000h (non-snooped) and will return
“unsuccessful completion”.
• Writes: Sent to DRAM address 000C_0000h (non-snooped) with byte enables all
disabled Peer writes from PEG to DMI are not supported.
If PEG bus master enable is not set, all reads and writes are treated as unsupported
requests.
2.3.13.2.1
TC/VC Mapping Details
• VC0 (enabled by default)
— Snoop port and Non-snoop Asynchronous transactions are supported.
— Internal Graphics GMADR writes can occur. Unlike FSB chipsets, these will NOT
be snooped regardless of the snoop not required (SNR) bit.
— Internal Graphics GMADR reads (unsupported).
— Peer writes are only supported between PEG ports. PEG to DMI peer write
accesses are NOT supported.
— MSI can occur. These will route to the cores (IntLogical/IntPhysical) regardless
of the SNR bit.
• VC1 is not supported.
• VCm is not supported.
