ia-32_volume1_basic-arch

Section 55 sse instructions and chapter 10 programming

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Unformatted text preview: a single physical processor to execute two or more separate code streams (threads) concurrently using shared execution resources. HT Technology is one form of hardware multi-threading capability in IA-32 processor families. It differs from multi-processor capability using separate physically distinct packages with each physical processor package mated with a physical socket. HT Technology provides hardware multi-threading capability with a single physical package by using shared execution resources in a processor core. Architecturally, an IA-32 processor that supports HT Technology consists of two or more logical processors, each of which has its own IA-32 architectural state. Each logical processor consists of a full set of IA-32 data registers, segment registers, control registers, debug registers, and most of the MSRs. Each also has its own advanced programmable interrupt controller (APIC). Figure 2-5 shows a comparison of a processor that supports HT Technology (implemented with two logical processors) and a traditional dual processor system. IA-32 Processor Supporting Hyper-Threading Technology AS AS Traditional Multiple Processor (MP) System AS AS Processor Core Processor Core Processor Core IA-32 processor IA-32 processor IA-32 processor Two logical processors that share a single core Each processor is a separate physical package AS = IA-32 Architectural State OM16522 Figure 2-5. Comparison of an IA-32 Processor Supporting Hyper-Threading Technology and a Traditional Dual Processor System Unlike a traditional MP system configuration that uses two or more separate physical IA-32 processors, the logical processors in an IA-32 processor supporting HT Technology share the core resources of the physical processor. This includes the execution 2-18 Vol. 1 INTEL 64 AND IA-32 ARCHITECTURES engine and the system bus interface. After power up and initialization, each logical processor can be independently directed to execute a specified thread, interrupted, or halted. HT Technology leverages the process and thread-level parallelism found in contemporary operating systems and high-performance applications by providing two or more logical processors on a single chip. This configuration allows two or more threads1 to be executed simultaneously on each a physical processor. Each logical processor executes instructions from an application thread using the resources in the processor core. The core executes these threads concurrently, using out-of-order instruction scheduling to maximize the use of execution units during each clock cycle. 2.2.5.1 Some Implementation Notes All HT Technology configurations require: A processor that supports HT Technology A chipset and BIOS that utilize the technology Operating system optimizations See http://www.intel.com/products/ht/hyperthreading_more.htm for information. At the firmware (BIOS) level, the basic procedures to initialize the logical processors in a processor supporting HT Technology are the same as those for...
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