Intel NETWORK PROCESSOR IXP2800 - Manual (Page 98)

98 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
Intel XScale ® Core
3.6.1.2 Mini-Data Cache Overview
The mini-data cache is a 2-Kbyte, 2-way set associative cache; this means there are 32 sets with
each set containing 2 ways. Each way of a set contains 32 bytes (one cache line) and one valid bit.
There also exist 2 dirty bits for every line, one for the lower 16 bytes and the other one for the
upper 16 bytes. When a store hits the cache, the dirty bit associated with it is set. The replacement
policy is a round-robin algorithm.
Figure 23 shows the cache organization and how the data address is used to access the cache.
The mini-data cache is virtually addressed and virtually tagged and supports the same caching
policies as the data cache. However, lines cannot be locked into the mini-data cache.
Figure 23. Mini-Data Cache Organization
A9692-01
32 bytes (cache line)
Tag
Data Address (Virtual)
Note: CAM = Content Addressable Memory
Set Index
Word Select
Byte Alignment
Sign Extension
Data Word
(4 bytes to Destination Register)
Word Byte
way 0
Set 31
Set 1
way 1
31 5 4 2 1 0 10 9
Set 0
Byte Select
Tag
This example
shows Set 0 being
selected by the
Set Index
32 bytes (cache line) way 0
way 1
32 bytes (cache line) way 0
way 1