Intel Itanium 2 Processor - Manual (Page 92)

92 Datasheet
Signals Reference
Any memory access transaction addressing a memory region that is less than 64 GB (that is,
Aa[49:36]# are all zeroes) must set ASZ[1:0]# to 01. Any memory access transaction addressing a
memory region that is equal to or greater than 64 GB (that is, Aa[49:36]# are not all zeroes) must
set ASZ[1:0]# to 10. All observing bus agents that support the 64 GByte (36-bit) address space
must respond to the transaction when ASZ[1:0]# equals 01. All observing bus agents that support
larger than the 64 GByte (36-bit) address space must respond to the transaction when ASZ[1:0]#
equals 01 or 10.
A.1.6 ATTR[3:0]# (I/O)
The ATTR[3:0]# signals are the attribute signals. They are driven by the request initiator during the
second clock of the Request Phase on the Ab[35:32]# pins. The ATTR[3:0]# signals are valid for
all transactions. The ATTR[3]# signal is reserved. The ATTR[2:0]# are driven based on the
memory type. Please refer to
Table A-2 .
A.1.7 BCLKp/BCLKn (I)
The BCLKp and BCLKn differential clock signals determine the bus frequency. All agents drive
their outputs and latch their inputs on the differential crossing of BCLKp and BCLKn on the
signals that are using the common clock latched protocol.
BCLKp and BCLKn indirectly determine the internal clock frequency of the Itanium 2 processor.
Each Itanium 2 processor derives its internal clock by multiplying the BCLKp and BCLKn
frequency by a ratio that is defined and allowed by the power-on configuration.
A.1.8 BE[7:0]# (I/O)
The BE[7:0]# signals are the byte-enable signals for partial transactions. They are driven by the
request initiator during the second Request Phase clock on the Ab[15:8]# pins.
Table A-1. Address Space Size
ASZ[1:0]#
Memory Address
Space
Memory Access
Range
0 0 Reserved Reserved
0 1 36-bit 0 to (64 GByte - 1)
1 0 50-bit 64 GByte to
(1 Pbyte –1)
1 1 Reserved Reserved
Table A-2. Effective Memory Type Signal Encoding
ATTR[2:0]# Description
000 Uncacheable
100 Write Coalescing
101 Write-Through
110 Write-Protect
111 Writeback