System Wrap And Deliver Data; Wrap Interleave Order - Compaq EV68A Hardware Reference Manual

point is the QW pointed to by the 21264/EV68A; however, some systems may find it
more beneficial to begin the transfer elsewhere. The system must always indicate the
starting point to the 21264/EV68A. The wrap order for subsequent QWs is interleaved.
Table 4–29 defines the method for systems to specify wrap and deliver data.
Table 4–29 System Wrap and Deliver Data
Source/
Destination SysDc[4:2]
Memory 100 (ReadData)
Memory 101(ReadDataDirty)
Memory 110 (ReadDataShared)
Memory 111(Read DataShared/Dirty)
Memory 010 (WriteData)
I/O 100 (ReadData)
I/O 100 (ReadData)
I/O 100 (ReadData)
I/O 010 (WriteData)
I/O 010 (WriteData)
I/O 010 (WriteData)
Note 1:
Note 2:
Table 4–30 defines the interleaved scheme for the wrap order.
Table 4–30 Wrap Interleave Order
First quadword
Second quadword
Third quadword
Fourth quadword
Fifth quadword
21264/EV68A Hardware Reference Manual
SysDc[1:0]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[4:3]
SysAddOut_L[4:3]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
SysAddOut_L[5:4]
Transfers to and from the 21264/EV68A have eight data cycles for a total
of eight quadwords. The starting point is defined by the system. The pre-
ferred starting point is the one pointed to by SysAddOut_L[5:4]. Systems
can insert the SysAddOut_L[5:4] into the SysDc[1:0] field of the com-
mand. See Table 4–30 for the wrap order.
LW and byte/word read transfers differ from all other transfers. The system
unloads only four QWs of data into eight data cycles by sending each QW
twice (referred to as double-pumped data transfer). The first QW returned
is determined by SysAddOut_L[4:3]. The system again may elect to
choose its own starting point for the transfer and insert that value into
SysDc[1:0]. See Table 4–31 for the wrap order.
PA Bits [5:3] of Transferred QW
000 010
001 011
010 000
011 001
100 110
System Port
Size
Block (64 Bytes)
Block (64 Bytes)
Block (64 Bytes)
Block (64 Bytes)
Block (64 Bytes)
QW (8-64 Bytes)
LW(4-32 Bytes)
Byte/Word
QW (8-64 Bytes)
LW(4-32 Bytes)
Byte/Word
100 110
101 111
110 100
111 101
000 010
Cache and External Interfaces
Rules
See Note 1
See Note 1
See Note 1
See Note 1
See Note 1
See Note 1
See Note 2
See Note 2
See Note 1
See Note 1
See Note 1
4–37