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260 Microarchitecture for AMD Athlon™ 64 and AMD Opteron™ Processors Appendix A
25112 Rev. 3.06 September 2005
Software Optimization Guide for AMD64 Processors
The L2 cache in the AMD Athlon XP, AMD Athlon™ 64, and AMD Opteron processors is 16-way
associative.
A.17 Write-combining
See Appendix B, “Implementation of Write-Combining,” on page 263 for detailed information about
write-combining.
A.18 Buses for AMD Athlon™ 64 and AMD Opteron™
Processor
AMD Athlon 64 and AMD Opteron processors feature an integrated memory controller and
HyperTransport technology for interfacing to I/O devices. These integrated features, along with other
logic, bring the Northbridge functionality onto the processor.
A.19 Integrated Memory Controller
AMD Athlon 64 and AMD Opteron processors provide an integrated low-latency, high-bandwidth
DDR memory controller.
The memory controller supports:
• DRAM devices that are 4, 8, and 16 bits wide.
• Interleaving memory within DIMMs.
• ECC checking with double-bit detection and single-bit correction.
For specifications on a certain processor’s memory controller, see the data sheet for that processor.
For information on how to program the memory controller, see the BIOS and Kernel Developer’s
Guide for AMD Athlon
TM
64 and AMD Opteron
TM
Processors, order# 26094.
A.20 HyperTransport™ Technology Interface
HyperTransport technology is a scalable, high-speed, low-latency, point-to-point, packetized link
that:
• Enables data transfer rates of up to 8 Gbytes/s (4 Gbytes/s in each direction simultaneously with a
16-bit link).
• Simplifies connectivity by replacing legacy buses and bridges.
• Reduces latencies and bottlenecks within systems.