blog: hpc cpu architecture

YaeBlog/source/posts/hpc-2025-cpu-architecture.md

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+---
+title: High Performance Computing 2025 SP CPU Architecture
+date: 2025-03-13T23:59:08.8167680+08:00
+tags:
+- 学习资料
+- 高性能计算
+---
+
+How to use the newly available transistors?
+
+<!--more-->
+
+Parallelsim:
+
+Instruction Level Parallelism(ILP):
+
+- **Implicit/transparent** to users/programmers.
+- Instruction pipelining.
+- Superscalar execution.
+- Out of order execution.
+- Register renaming.
+- Speculative execution.
+- Branch prediction.
+
+Task Level Parallelism(TLP):
+
+- **Explicit** to users/programmers.
+- Multiple threads or processes executed simultaneously.
+- Multi-core processors.
+
+Data Parallelism:
+
+- Vector processors and SIMD.
+
+Von Neumann Architecture: the **stored-program** concept. Three components: processor, memory and data path.
+
+Bandwidth: the gravity of modern computer system.
+
+## Instruction Pipelining
+
+Divide incoming instructions into a series of sequential steps performed by different processor unit to keep every part of the processor busy.
+
+Superscalar execution can execute more than one instruction during a clock cycle.
+
+Order of order execution.
+
+Very long instruction word(VLIW): allows programs to explicitly specify instructions to execute at the same time.
+
+EPIC: Explicit parallel instruction computing.
+
+Move the complexity of instruction scheduling from the CPU hardware to the software compiler:
+
+- Check dependencies between instructions.
+- Assign instructions to the functional units.
+- Determine when instructions are initiated placed together into a single word.
+
+![image-20250313184421305](./hpc-2025-cpu-architecture/image-20250313184421305.png)
+
+Comparisons between different architecture:
+
+![image-20250313184732892](./hpc-2025-cpu-architecture/image-20250313184732892.png)
+
+## Multi-Core Processor Gala
+
+Symmetric multiprocessing(SMP): a multiprocessor computer hardware and software architecture.
+
+Two or more identical processors are connected to a **single shared main memory** and have full access to all input and output devices.
+
+> Current trend: computer clusters, SMP computers connected with network.
+
+Multithreading: exploiting thread-level parallelism.
+
+Multithreading allows multiple threads to share the functional units of a single processor in an overlapping fashion **duplicating only private state**. A thread switch should be much more efficient than a process switch.
+
+Hardware approaches to multithreading: 
+
+**fine-grained multithreading**:
+
+- Switches between threads on each clock.
+- Hide the throughput losses that arise from the both short and long stalls.
+- Disadvantages: slow down the execution of an individual thread.
+
+**Coarse-grained multithreading**:
+
+- Switch threads only on costly stalls.
+- Limited in its ability to overcome throughput losses
+
+**Simultaneous multithreading(SMT)**:
+
+- A variation on fine-grained multithreading
+
+![image-20250313190913475](./hpc-2025-cpu-architecture/image-20250313190913475.png)
+
+## Data Parallelism: Vector Processors
+
+Provides high-level operations that work on vectors.
+
+Length of the array also varies depending on hardware.
+
+SIMD and its generalization in vector parallelism approach improved efficiency by the same operation be performed on multiple data elements.