Sun Microelectronics
10
UltraSPARC User’s Manual
1.3.10 Memory Interface Unit (MIU)
The MIU handles all transactions to the system controller; for example, external
cache misses, interrupts, snoops, writebacks, and so on. The MIU communicates
with the system at some model-dependent fraction of the UltraSPARC frequency.
Table 1-5 shows the possible ratios between the processor and system clock fre-
quencies for each UltraSPARC model.
1.4 UltraSPARC Subsystem
Figure 1-2 shows a complete UltraSPARC subsystem, which consists of the
UltraSPARC processor, synchronous SRAM components for the E-Cache tags and
data, and two UltraSPARC Data Buffer (UDB) chips. The UDBs isolate the
E-Cache from the system, provide data buffers for incoming and outgoing system
transactions, and provide ECC generation and checking.
Figure 1-2
UltraSPARC Subsystem
Table 1-5
Model-Dependent Processor : System Clock Frequency Ratios
Frequency Ratio
UltraSPARC-I
UltraSPARC-II
2 : 1
✓
✓
3 : 1
✓
✓
4 : 1
✓
E-Cache Data SRAM
UDB
E-Cache Tag SRAM
System
Data Bus
System
Address Bus
E-Cache Data
Tag Data
Tag Address
Data Address
UltraSPARC
Processor
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