Compaq EV68A specifications 12describes the field definitions for Tables 4-10and, Hit Mode

System Port

Table 4–10 Bank Interleave on Cache Block Boundary Mode of Operation (Continued)

		SysAddOut_L[14:2]				SysAddOut_L[1]	SysAddOut_L[0]
Cycle 2			PA[27:22], PA[12:6]			PA[35]	PA[37]
Cycle 3	M2	Mask[7:0]		CH	ID[2:0]	PA[40]	PA[42]
Cycle 4	RV	PA[21:13], PA[5:3]				PA[39]	PA[41]

4.7.3.2 Page Hit Mode

Table 4–11shows the command format for page hit mode (21264/EV68A-to-system).

Table 4–11 Page Hit Mode of Operation

		SysAddOut_L[14:2]					SysAddOut_L[1]	SysAddOut_L[0]
Cycle 1	M1	Command[4:0]			PA[31:25]		PA[32]	PA[33]
Cycle 2			PA[24:12]				PA[11]	PA[34]
Cycle 3	M2	Mask[7:0]		CH		ID[2:0]	PA[35]	PA[37]
Cycle 4	RV	PA[34:32], PA[11:3]					PA[36]	PA[38]

Table 4–12describes the field definitions for Tables 4–10and 4–11.

Table 4–12 21264/EV68A-to-System Command Fields Definitions

SysAddOut Field	Definition
M1	When set, reports a miss to the system for the oldest probe.
	When clear, has no meaning.
Command[4:0]	The 5-bit command field is defined in Table 4–14.
SysAddOut[1:0]	This field is needed for systems with greater than 32GB of memory, up to a maximum of 8
	Terabyte (8TB). Cost-focused systems can tie these bits high and use a 13-bit command/
	address field.
M2	When set, reports that the oldest probe has missed in cache. Also, this bit is set for system-
	to-21264/EV68A probe commands that hit but have no data movement (see the CH bit,
	below).
	When clear, has no meaning.
	M1 and M2 are not asserted simultaneously. Reporting probe results as soon as possible is
	critical to high-speed operation, so when a result is known the 21264/EV68A uses the ear-
	liest opportunity to send an M signal to the system. M bit assertion can occur either in a
	valid command or a NZNOP.
ID[2:0]	The ID number for the MAF, VDB, or WIOB associated with the command.
RV	If set, validates this command.
	In speculative read mode (optional), RV = 1 validates the command and RV = 0 indicates
	a NOP.
	For all nonspeculative commands RV = 1.
Mask[7:0]	The byte, LW, or QW mask field for the corresponding I/O commands.
CH	The cache hit bit is asserted, along with M2, when probes with no data movement hit in
	the Dcache or Bcache. This response can be generated by a probe that explicitly indicates
	no data movement or a ReadIfDirty command that hits on a valid but clean or shared
	block.

4–20Cache and External Interfaces 21264/EV68A Hardware Reference Manual