User guide

Figure 6–3 21071-CA Block Diagram
ML013275
Tag
Compare
Address
Generation
tagadr<31:17>
adr<33:5>
Write
Buffer
Address
Row and
Column
Generation
Memory
Control
Memory
Bank
Generation
Write Address
Write Bank
Read Bank
Read Address
b<3:0>_ras<1:0>b_l
SysBus
and
L2 Cache
Control
Dath Path Control
L2 Cache Control
SysBus Control
8
b<1:0>_cas<3:0>b_l
8
b<3:0>_ras<1:0>_l
8
b0<3:0>_we_l
4
b<3:0>_we_l
4
b0<3:0>_adr<11:0>
48
Row
Col
The following list summarizes the functions of the DECchip 21071-CA:
• Arbitrates between the CPU and the 21071-DA for control of the system bus.
• Controls filling the Bcache and extracting victims on CPU-initiated
transactions.
• Controls probing the Bcache on direct-memory access (DMA) transactions and
invalidating the Bcache on DMA write hits.
• Controls the loading of the I/O write buffer and the DMA read buffer.
• Uses fast-page mode on the DRAMs to improve performance on DMA burst
reads and memory write transactions.
Cache and Memory Subsystem 6–3