Compaq 21264 - Manual (Page 220)

7–12 Initialization and Configuration Alpha 21264/EV67 Hardware Reference Manual
Array Initialization
The 21264/EV67 waits until Reset_L is deasserted before transitioning from the
WAIT_RESET state. The 21264/EV67 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/EV67 performs BiST and the SROM
loading procedure.
After BiST and SROM loading have completed, SromOE_L deasserts and the 21264/
EV67 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/EV67 to generate and manipulate cache
blocks before the system interface has been initialized. Within the 21264/EV67, 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 7–9 to 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