29 September 1997 – Subject To Change
Clocks, Cache, and External Interface
4–29
21164PC-Initiated System Transactions
WRITE BLOCK
0110
Request to write a block. When the 21164PC wants to write a
32-byte block of data to noncached memory, it drives the com-
mand, address, and first INT16 of data on a sysclk edge. The
21164PC outputs the next INT16 of data when dack_h is
received. When the system asserts cack_h, the 21164PC
removes the command and address from the bus and begins the
write of the Bcache. Signal cack_h can be asserted before all
the data is removed.
—
0111
Reserved.
READ MISS0
1000
Request for data. This command indicates that the 21164PC
has probed its caches and that the addressed block is not
present.
READ MISS1
1001
Request for data. This command indicates that the 21164PC
has probed its caches and that the addressed block is not
present.
—
1010
Reserved.
—
1011
Reserved.
BCACHE
VICTIM
1100
Bcache victim should be removed. If there is a victim buffer in
the system, this command is used to pass the address of the vic-
tim to the system. The READ MISS command that produced
the victim precedes the BCACHE VICTIM command. Signal
victim_pending_h is asserted during the READ MISS com-
mand to indicate that a BCACHE VICTIM command is wait-
ing, and that the Bcache is starting the read of the victim data.
—
1101
Reserved.
—
1110
Reserved.
—
1111
Reserved.
Table 4–8 21164PC-Initiated Interface Commands
(Sheet 2 of 2)
Command
cmd_h
<3:0>
Description