Compaq EV68A specifications Restriction 47 Cache Eviction for Single-Bit Cache Errors

Models: EV68A

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Restriction 47: Cache Eviction for Single-Bit Cache Errors

If "CBOX_ERR[C_ADDR]" has not changed when the CRD_HANDLER is re- entered, or "CBOX_ERR[C_STAT] == 0x0", all cache locations should to be evicted to avoid the live lock described above.

;Sample code for evicting cache.

;This method loads a 64K block, then exits the CRD_HANDLER

;to check if the sberr has been evicted. If not it loads the next 64K block.

;In the sample code below,

;sx is a shadow register

;ldi is a macro that loads a 64-bit constant into the specified register

full_scrub:

 

 

 

hw_ldq/p

s5, 104(r31)

 

ldi

s1, ^x200

; Loop dec value

ldi

s2, ^x1C0

; Start offset

ldi

s3, ^x10000

; Block size (64K -> size of dcache)

ldi

s4, ^x2000000

; 2X bcache size

addq

s3,s5,s5

 

ble

s5, s4, <.+4>

; Skip next instruction if ADDR

 

 

 

; .le. 2X bcache

bis

r31, r31, s5

; Set ADDR = 0x0

hw_stq/p

s5, 104(r31)

; Store ADDR for next pass thru

subq

s5, s2, s5

 

mb

 

 

; Make sure no speculative loads

 

 

 

; happen in the CRD handler

.align

4, NOP_OPCODE

;

blbc

r31, <.+4>

;

br

r31, <.-4>

;V

.align

4, NOP_OPCODE

; Make sure no speculative loads

 

 

 

; happen in the CRD handler

next_reread:

;******** four cache blocks

;Evict dcache by prefetching to all dcache indexes.

;use 'hw_ldl r31 xxxx' Normal Prefetch

;Do not use 'hw_ldq/p r31 xxx' Prefetch,

;Evict Next because this will always access the same set in dcache.

hw_ldl/p

r31,^x1C0(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x180(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x140(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x100(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^xC0(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x80(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x40(s5)

; Re-read the bad block QW #0

hw_ldl/p

r31,^x00(s5)

; Re-read the bad block QW #0

subq

s5,

s1, s5

; Decrement addr

subq

s3,

s1, s3

; Decrement counter

ble

s3, <.+4>

 

br

r31, next_reread

 

bsr

s7, sys__cbox

; Read and clean cbox error ipr

21264/EV68A Hardware Reference Manual

PALcode Restrictions and Guidelines D–23

Page 319
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Compaq EV68A Restriction 47 Cache Eviction for Single-Bit Cache Errors, PALcode Restrictions and Guidelines D-23