Compaq EV68A lists the data movement selected by Probe43, Data Movement Selection by Probe43

System Port

Table 4–20describes the system-to-21264/EV68A probe commands fields descriptions.

Table 4–20 System-to-21264/EV68A Probe Commands Fields Descriptions

SysAddIn_L[14:0]

FieldDescription

Probe[4:0]	Probe type and next tag state (see Tables 4–21and 4–22).
SysDc[4:0]	Controls data movement in and out of the 21264/EV68A. See Table 4–24for a list of data
	movement types.
RVB	Clears the victim or I/O write buffer (IOWB) valid bit specified in ID[3:0].
RPB	Clears probe valid bit specified in ID[2:0].
A	Command acknowledge. When set, the 21264/EV68A decrements its command outstand-
	ing counter (SYSBUS_ACK_LIMIT[4:0]).
ID[3:0]	Identifies the victim data buffer (VDB) number or the I/O write buffer (IOWB) number.
	Bit [3] is only asserted for the IOWB.
C	Commit bit. This bit decrements the uncommitted event counter (MB_CNTR) used for
	MB acknowledge.
	The probe command field Probe[4:0] has two sections, Probe[4:3] and Probe[2:0].
	Table 4–21lists the data movement selected by Probe[4:3].

Table 4–21 Data Movement Selection by Probe[4:3]

Probe[4:3]	Data Movement Function
00	NOP
01	Read if hit, supply data to system if block is valid.
10	Read if dirty, supply data to system if block is valid/dirty.
11	Read anyway, supply data to the system at index of probe.

Table 4–22lists the next cache block state selected by Probe[2:0].

Table 4–22 Next Cache Block State Selection by Probe[2:0]

Probe[2:0]	Next Tag State
000	NOP
001	Clean
010	Clean/Shared
011	Transition31: Clean		Clean/Shared
		Dirty	Invalid	Clean/Shared
100	Dirty/Shared	Dirty/Shared⇒
21264/EV68A Hardware Reference Manual⇒				Cache and External Interfaces 4–27