System Interface; Ev67 System And Bcache Interfaces - Compaq 21264 Hardware Reference Manual

Figure 4–1 21264/EV67 System and Bcache Interfaces
SysAddIn_L[14:0]
SysAddInClk_L
SysAddOut_L[14:0]
SysAddOutClk_L
SysVref
SysData_L[63:0]
SysCheck_L[7:0]
SysDataInClk_H[7:0]
SysDataOutClk_L[7:0]
SysDataInValid_L
SysDataOutValid_L
SysFillValid_L
BcAdd_H[23:4]
21264
BcLoad_L
BcData_H[127:0]
BcCheck_H[15:0]
BcDataInClk_H[7:0]
BcDataOutClk_ x [3:0]
BcDataOE_L
BcDataWr_L
BcTag_H[42:20]
BcTagInClk_H
BcTagOutClk_ x
BcVref
BcTagWr_L
BcTagOE_L
BcTagValid_H
BcTagDir ty_H
BcTagShared_H
BcTagParity_H
IRQ_H[5:0]

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.
Alpha 21264/EV67 Hardware Reference Manual
Introduction to the External Interfaces
[23:4] [23:6]
Data Tag
[23:6]
Status
System
FM-05818B-EV67
Cache and External Interfaces
4–3