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Alpha 21264/EV67 Hardware Reference Manual
Cache and External Interfaces 4–3
Introduction to the External Interfaces
Figure 4–1 21264/EV67 System and Bcache Interfaces
4.1.1 System Interface
This section introduces the system (external) bus interface. The system interface is
made up of two unidirectional 15-bit address buses, 64 bidirectional data lines, eight
bidirectional check bits, two single-ended unidirectional clocks, and a few control pins.
The 15-bit address buses provide time-shared address/command/ID in two or four
GCLK cycles. The Cbox controls the system interface.
BcData_H[127:0]
BcAdd_H[23:4]
BcCheck_H[15:0]
BcDataInClk_H[7:0]
BcDataOutClk_
x
[3:0]
BcDataOE_L
BcDataWr_L
21264
SysAddOut_L[14:0]
SysAddInClk_L
SysAddIn_L[14:0]
SysAddOutClk_L
SysVref
FM-05818B-EV67
SysDataInClk_H[7:0]
SysCheck_L[7:0]
SysData_L[63:0]
SysDataOutClk_L[7:0]
SysDataInValid_L
SysFillValid_L
SysDataOutValid_L
BcTag_H[42:20]
BcTagInClk_H
BcTagOutClk_
x
BcVref
BcTagParity_H
BcTagWr_L
BcTagOE_L
BcTagValid_H
BcTagDirty_H
BcTagShared_H
BcLoad_L
Data Tag Status
System
IRQ_H[5:0]
[23:4] [23:6] [23:6]