Compaq EV68A specifications Array Initialization, Initialization Mode Processing

Array Initialization

The 21264/EV68A waits until Reset_L is deasserted before transitioning from the WAIT_RESET state. The 21264/EV68A ramps up the PLL until the state machine enters the WAIT_ClkFwdRst0 state. Note that the system must assert ClkFwdRst_H before the state machine enters the WAIT_ClkFwdRst0 state. Then, similarly to the other flows, SromOE_L is asserted and the system waits for the deassertion of

ClkFwdRst_H.

On the deassertion of ClkFwdRst_H, the 21264/EV68A performs BiST and the SROM loading procedure.

After BiST and SROM loading have completed, SromOE_L deasserts and the 21264/ EV68A waits for ClkFwdRst_H to deassert before starting the external clocks and, like the other flows, waits for 264 cycles before starting instructions.

7.5 Array Initialization

The following arrays are initialized by BiST:

•Icache and Icache tag

•Dcache, Dcache tag, and Duplicate Dcache tag

•Branch history table

The external second-level cache (Bcache) is disabled by Reset_L.

The Bcache must be initialized by PALcode before it is enabled.

7.6 Initialization Mode Processing

The initialization mode allows the 21264/EV68A to generate and manipulate cache blocks before the system interface has been initialized. Within the 21264/EV68A, the Cbox configuration registers are divided into the WRITE_ONCE and the WRITE_MANY shift register chains (see Sections 5.4.3 and 5.4.4). The WRITE_ONCE chain is loaded from the SROM during reset processing, and contains information such as the clock forwarding setup values. The WRITE_MANY chain can be written many times using MTPR instructions.

The WRITE_MANY chain contains the following CSRs that are important to initializa- tion mode, which must be set to the values in Table 7–9to initialize the Bcache.

Table 7–9 WRITE_MANY Chain CSR Values for Bcache Initialization

WRITE_MANY Chain CSRs	Required Value at Initialization Mode
BC_ENABLE	1
	The duplicate bits for BC_ENABLE in [14:12] must
	be 0 during initialization mode.
BC_SIZE[3:0]	The exact size or maximum size of the Bcache.
INVAL_TO_DIRTY_ENABLE[1:0]	1
SET_DIRTY_ENABLE[2:0]	0
INIT_MODE	1

7–12Initialization and Configuration 21264/EV68A Hardware Reference Manual