Compaq EV67, 21264 specifications Cbox Writeonce Chain Order, 34Internal Processor Registers

Cbox CSRs and IPRs

•Only a brief description of each CSR is given. The functional description of these CSRs is contained in Chapter 4.

•The order of multibit vectors is [MSB:LSB], so the LSB is first bit in the Cbox chain.

Table 5–24describes the Cbox WRITE_ONCE chain order from LSB to MSB.

Table 5–24 Cbox WRITE_ONCE Chain Order

Cbox WRITE_ONCE Chain Description

32_BYTE_IO[0] SKEWED_FILL_MODE[0] SKEWED_FILL_MODE[0] DCVIC_THRESHOLD[7:0]

BC_CLEAN_VICTIM[0] SYS_BUS_SIZE[1:0] SYS_BUS_FORMAT[0] SYS_CLK_RATIO[4:1]

DUP_TAG_ENABLE[0] PRB_TAG_ONLY[0] FAST_MODE_DISABLE[0] BC_RDVICTIM[0] BC_CLEAN_VICTIM[0]

RDVIC_ACK_INHIBIT

SYSBUS_MB_ENABLE SYSBUS_ACK_LIMIT[0:4] SYSBUS_VIC_LIMIT[0:2] BC_CLEAN_VICTIM[0] BC_WR_WR_BUBBLE[0] BC_RD_WR_BUBBLES[0:5] BC_RD_RD_BUBBLE[0]

BC_SJ_BANK_ENABLE BC_WR_RD_BUBBLES[0:3]

Enable 32_BYTE I/O mode.

Asserted when Bcache is at 1.5X ratio.

Duplicate of prior bit.

Threshold of the number of Dcache victims that will accumulate before streamed write transactions to the Bcache are initiated. The Cbox can accumulate up to six victims for streamed Dcache pro- cessing. This register is programmed with the decoded value of the threshold count.

Enable clean victims to the system interface.

Size of SysAddOut and SysAddOut buses.

Indicates system bus format.

Speed of system bus.
Code	Multiplier
0001	1.5X
0010	2.0X
0100	2.5X
1000	3.0X

Enable duplicate tag mode in the 21264/EV67.

Enable probe-tag only mode in the 21264/EV67.

When asserted, disables fast data movement mode.

Enables RdVictim mode on the pins.

Duplicate CSR.

Enable inhibition of incrementing acknowledge counter for RdVic commands.

Enable MB commands offchip.

Sysbus acknowledge limit CSR.

Limit for victims.

Duplicate CSR.

Write to write GCLK bubble.

Read to write GCLK bubbles for the Bcache interface.

Read to read GCLK bubble for banked Bcaches.

Enable bank mode for Bcache.

Write to read GCLK bubbles.

5–34Internal Processor Registers Alpha 21264/EV67 Hardware Reference Manual