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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Reference Number: 306262-004US
61
Functional Overview—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Intel XScale processor features include:
• Seven/eight-stage super-pipeline promotes high-speed, efficient performance
• 128-entry branch target buffer keeps pipeline filled with statistically correct branch
choices
• 32-entry instruction memory-management unit for logical-to-physical address
translation, access permissions, and Instruction-Cache (I-cache) attributes
• 32-entry data-memory management unit for logical-to-physical address
translation, access permissions, Data-Cache (D-Cache) attributes
• 32-Kbyte instruction cache can hold entire programs, preventing stalls caused by
multi-cycle memory accesses
• 32-Kbyte data cache reduces stalls caused by multi-cycle memory accesses
• 2-Kbyte mini-data cache for frequently changing data streams avoids “thrashing”
of the D-cache
• Four-entry, fill-and-pend buffers to promote efficiency by allowing “hit-under-miss”
operation with data caches
• Eight-entry write buffer allows the Intel XScale processor to continue execution
while data is written to memory
• Multiple-accumulate coprocessor that can do two simultaneous, 16-bit, SIMD
multiplies with 40-bit accumulation for efficient, high-quality media and signal
processing
• Performance monitoring unit (PMU) furnishing two 32-bit event counters and one
32-bit cycle counter for analysis of hit rates, etc.
This PMU is for the Intel XScale processor only. An additional PMU is supplied for
monitoring of internal bus performance.
• JTAG debug unit that uses hardware break points and 256-entry trace history
buffer (for flow-change messages) to debug programs
• Supports big-endian and little-endian byte ordering