Compaq 21264, EV67 specifications Ecb I/O, Mb/Wmb

Models: 21264 EV67

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Physical Address Considerations

Prefetches (LDL, LDF, LDG, LDT, LDBU, LDWU) to R31 use the LDx flow, and prefetch with modify intent (LDS) uses the STx flow. If the prefetch target is addressed to I/O space, the upper address bit is cleared, converting the address to memory space (PA[42:6] ). Notes follow the table.

Table 4–1 Translation of Internal References to External Interface Reference

Instruction

DcHit

DcW

BcHit

BcW

Status and Action

LDx Memory

1

X

X

X

Dcache hit, done.

LDx Memory

0

X

1

X

Bcache hit, done.

LDx Memory

0

X

0

X

Miss, generate RdBlk command.

LDx I/O

X

X

X

X

RdBytes, RdLWs, or RdQWs based on size.

Istream Memory

1

X

X

X

Dcache hit, Istream serviced from Dcache.

Istream Memory

0

X

1

X

Bcache hit, Istream serviced from Bcache.

Istream Memory

0

X

0

X

Miss, generate RdBlkI command.

STx Memory

1

1

X

X

Store Dcache hit and writable, done.

STx Memory

1

0

X

X

Store hit and not writable, set dirty flow (note 1).

STx Memory

0

X

1

1

Store Bcache hit and writable, done.

STx Memory

0

X

1

0

Store hit and not writable, set-dirty flow (note 1).

STx Memory

0

X

0

X

Miss, generate RdBlkMod command.

STx I/O

X

X

X

X

WrBytes, WrLWs, or WrQWs based on size.

STx_C Memory

0

X

X

X

Fail STx_C.

STx_C Memory

1

0

X

X

STx_C hit and not writable, set dirty flow (note 1).

STx_C I/O

X

X

X

X

Always succeed and WrQws or WrLws are generated,

 

 

 

 

 

based on the size.

WH64 Memory

1

1

X

X

Hit, done.

WH64 Memory

1

0

X

X

WH64 hit not writable, set dirty flow (note 1).

WH64 Memory

0

X

1

1

WH64 hit dirty, done.

WH64 Memory

0

X

1

0

WH64 hit not writable, set dirty flow (note 1).

WH64 Memory

0

X

0

X

Miss, generate InvalToDirty command (note 2).

WH64 I/O

X

X

X

X

NOP the instruction. WH64 is UNDEFINED for I/O

 

 

 

 

 

space.

ECB Memory

X

X

X

X

Generate evict command (note 3).

ECB I/O

X

X

X

X

NOP the instruction. ECB instruction is UNDEFINED

 

 

 

 

 

for I/O space.

MB/WMB

X

X

X

X

Generate MB command (note 4). See Section 2.12.1.

TB Fill Flows

 

 

 

 

 

 

 

 

 

 

 

Alpha 21264/EV67 Hardware Reference Manual

Cache and External Interfaces 4–5

Page 93
Image 93
Compaq 21264, EV67 specifications Ecb I/O, Mb/Wmb