Microprocessor
Methods To Increase Performance:
•The number of transistors available has a huge effect on the performance of a processor.
•More transistors also allow for a technology called pipelining.
•Parallelism
1
ELEC6200-001, Fall 08
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Multi-core Architectures, Study notes of Advanced Computer Architecture
Multi-core Architectures, Software and Hardware multi-threading, SMT and CMP architectures, Design Issues
Typology: Study notes
2018/2019
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Microprocessor
Methods To Increase Performance:
- The number of transistors available has a huge effect on the performance of a processor.
- (^) More transistors also allow for a technology called pipelining.
- (^) Parallelism ELEC6200-001, Fall 08 1
Parallelism in Microprocessors
- (^) Pipelining is most prevalent ▫ Used in everything ▫ (^) Even microcontrollers ▫ Decreases cycle time ▫ (^) Allows up to 1 instruction per cycle (IPC) ▫ (^) No programming changes ▫ (^) Some Pentium 4s have more than 30 stages!
- (^) Parallelism classifications: Instruction level Loop level Thread level - Future trend Process level - Future trend ELEC6200-001, Fall 08 2
Superscalar pipeline
ELEC6200-001, Fall 08 4
Competing technologies
- (^) Simultaneous Multi Threading
- (^) Simultaneous Multi threading architecture is similar to that of the superscalar.
- (^) SMT processors support wide superscalar processors with hardware, to execute instructions from multiple thread concurrently.
- (^) Out-of-Order Execution
- Where instructions execute in any order that does not violate data dependencies.
- (^) Note that this technique is independent of both pipelining and superscalar ELEC6200-001, Fall 08 5
Why Multiprocessor Systems?
- (^) Single-core microprocessor performance increases are beginning to slow [1] due to:
- (^) Increasing power consumption (>100 W)
- (^) Increasing heat dissipation
- Diminishing performance gains from ILP & TLP
- (^) As a result manufactures are turning to a multi-core microprocessor approach
- (^) Multiple smaller energy efficient processing cores are integrated onto a single chip
- (^) Improves overall performance by performing more work concurrently
- (^) The latencies associated with chip-to-chip communication disappear, Shared data structures are much less of a problem. ELEC6200-001, Fall 08 7
Centralized architecture
- (^) Disadvantages of centralized architectures such as SMT and Superscalars are:
- Area increases quadratically with core’s complexity.
- Increase in cycle time – interconnect delays. Delay with wires dominate delay of critical path of CPU. Possible to make simpler clusters, but results in deeper pipeline and increase in branch misprediction penalty.
- Design verification cost high, due to complexity and single processor
- Large demand on memory system. ELEC6200-001, Fall 08 8
Case for single chip multiprocessors
- (^) Advances in the field of integrated chip processing.
- Gate density (More transistors per chip)
- Cost of wires
- (^) Large uniprocessors are no longer scaling in performance, because it is only possible to extract a limited amount of parallelism from a typical instruction stream using conventional superscalar instruction issue techniques. ELEC6200-001, Fall 08 10
CMP Architectures
- Two general types of multi-core or chip multiprocessor (CMP) architectures
- (^) Homogeneous CMPs – all processing elements (PEs) are the same
- (^) Heterogeneous CMPs – comprised of different PEs
- Homogenous dual-core processors for PCs are now available from all major
manufactures
- (^) Heterogeneous CMPs are available in the form of multiprocessor systems-on-chips
(MPSoCs)
ELEC6200-001, Fall 08 11
Multicore processor
- (^) A multi-core processor is a single computing component with two or more independent processing units called cores, which read and execute program instructions.
- (^) The instructions are ordinary CPU instructions (such as add, move data, and branch) but the single processor can run multiple instructions on separate cores at the same time, increasing overall speed for programs amenable to parallel computing.
- (^) Manufacturers typically integrate the cores onto a single integrated circuit die (known as a chip multiprocessor or CMP) or onto multiple dies in a single chip package.
- (^) The microprocessors currently used in almost all personal computers are multi-core.
http://csp2.epgpbooks.inflibnet.ac.in/chapter/thread-level-parallelism-s
mt-and-cmp/
Single-core
computer
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Single-core CPU chip
the single core 2 0