Compaq EV67, 21264 specifications 8PALcode Restrictions and Guidelines

Models: 21264 EV67

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Restriction 2 : No Multiple Writers to IPRs in Same Scoreboard Group

br

r31,palbase_init

 

palbase_init:

 

 

 

br

r0, br60

/* r0 <- current location */

br60: lda

r1, (EntryPoint-br60)(r0) /* r1 <- location of codebase */

mtpr

r1, EV6__PAL_BASE /* set up pal_base register */

bis

r31, 2, r0

 

mtpr

r0, EV6__VA_CTL

 

bis

r31, 8, r0

 

mtpr

r0, EV6__M_CTL

 

br

r0, jmp0

 

jmp0: addq

r0, (jmp1-jmp0+1), r0

hw_rets/jmp(r0)

 

jmp1:

 

 

 

lda

r1,

1(r31)

/* r1 <- cc_ctl enable bit */

sll

r1,

32, r1

 

mtpr

r1, EV6__CC_CTL

/* Enable/clear the cycle counter. */

/*

**Now initialize the dcache to allow the

**minidebugger so save gpr’s

*/

D.2 Restriction 2 : No Multiple Writers to IPRs in Same Scoreboard Group

For convenience of implementation, only one explicit writer (HW_MTPR) to IPRs that are in the same group can appear in the same fetch block (octaword-aligned octaword). Multiple explicit writers to IPRs that are not in the same scoreboard group can appear. If this restriction is violated, the IPR readers might not see the in-order state. Also, the IPR might ultimately end up with a bad value.

D.3 Restriction 4 : No Writers and Readers to IPRs in Same Score- board Group

This restriction is made for the convenience of microprocessor implementation.

An explicit reader of an IPR in a particular scoreboard group cannot follow an explicit writer (HW_MTPR) to an IPR in that same scoreboard group within one fetch block (octaword-aligned octaword). Also within one fetch block, an implicit reader of an IPR in a particular scoreboard group cannot follow an explicit writer (HW_MTPR) to an IPR in that scoreboard group. This restriction covers writes to DTB_PTE or DTB_TAG followed by LD, ST, or any memory operation, including all types of JMP instructions and HW_RET instructions that do not have the STALL bit set.

D–8PALcode Restrictions and Guidelines

Alpha 21264/EV67 Hardware Reference Manual

Page 306
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Compaq EV67, 21264 specifications 8PALcode Restrictions and Guidelines