PRIXP423BD Intel, PRIXP423BD Datasheet - Page 30

• Manufacturer Part Number: PRIXP423BD
• Manufacturer: Intel

Specifications of PRIXP423BD

• 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: Compliant

2.2.6
2.2.7
Intel
Datasheet
30
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IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
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 Intel XScale
processor 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 Intel XScale
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 Intel XScale
This prevents processor 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.
®
processor access to data at core frequencies. This prevents
Intel
®
processor access to data streams at core frequencies.
®
IXP42X product line and IXC1100 control plane processors
Document Number: 252479-006US
®
processor to access
August 2006