PRIXP425BD Intel, PRIXP425BD Datasheet - Page 27

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PRIXP425BD

Manufacturer Part Number
PRIXP425BD
Description
IC NETWRK PROCESSR 533MHZ 492BGA
Manufacturer
Intel
Datasheets

Specifications of PRIXP425BD

Processor Type
Network
Features
XScale Core
Speed
533MHz
Voltage
1.3V
Mounting Type
Surface Mount
Package / Case
492-BGA
Core Operating Frequency
533MHz
Package Type
BGA
Pin Count
492
Mounting
Surface Mount
Operating Temperature (max)
70C
Operating Temperature (min)
0C
Operating Temperature Classification
Commercial
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
866108

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Datasheet
2.2.6
2.2.7
The 32-Kbyte I-cache is 32-set/32-way associative, where each set contains 32 ways and each way
contains a tag address, a cache line of instructions (eight 32-bit words and one parity bit per word),
and a line-valid bit. For each of the 32 sets, 0 through 28 ways can be locked. Unlocked ways are
replaceable via a round-robin policy.
The I-cache can be enabled or disabled. Attribute bits within the descriptors — contained in the
ITLB of the IMMU — provide some control over an enabled I-cache.
When a needed line (eight 32-bit words) is not present in the I-cache, the line is fetched (critical
word first) from memory via a two-level, deep-fetch queue. The fetch queue allows the next
instruction to be accessed from the I-cache, but only when its data operands do not depend on the
execution results of the instruction being fetched via the queue.
Data Cache (D-Cache)
The D-cache can contain high-use data such as lookup tables and filter coefficients, allowing the
core access to data at core frequencies. This prevents core stalls caused by multi-cycle accesses to
external memory.
The 32-Kbyte D-cache is 32-set/32-way associative, where each set contains 32 ways and each
way contains a tag address, a cache line (32 bytes with one parity bit per byte) of data, two dirty
bits (one for each of two eight-byte groupings in a line), and one valid bit. For each of the 32 sets,
zero through 28 ways can be locked, unlocked, or used as local SRAM. Unlocked ways are
replaceable via a round-robin policy.
The D-cache (together with the mini-data cache) can be enabled or disabled. Attribute bits within
the descriptors, contained in the DTLB of the DMMU, provide significant control over an enabled
D-cache. These bits specify cache operating modes such as read and write allocate, write-back,
write-through, and D-cache versus mini-data cache targeting.
The D-cache (and mini-data cache) work with the load buffer and pend buffer to provide
“hit-under-miss” capability that allows the core to access other data in the cache after a “miss” is
encountered. The D-cache (and mini-data cache) works in conjunction with the write buffer for
data that is to be stored to memory.
Mini-Data Cache
The mini-data cache can contain frequently changing data streams such as MPEG video, allowing
the core access to data streams at core frequencies. This prevents core stalls caused by multi-cycle
accesses to external memory. The mini-data cache relieves the D-cache of data “thrashing” caused
by frequently changing data streams.
The 2-Kbyte, mini-data cache is 32-set/two-way associative, where each set contains two ways and
each way contains a tag address, a cache line (32 bytes with one parity bit per byte) of data, two
dirty bits (one for each of two eight-byte groupings in a line), and a valid bit. The mini-data cache
uses a round-robin replacement policy, and cannot be locked.
The mini-data cache (together with the D-cache) can be enabled or disabled. Attribute bits
contained within a coprocessor register specify operating modes write and/or read allocate,
write-back, and write-through.
Intel
®
IXP42X Product Line and IXC1100 Control Plane Processor
Functional Overview
27

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