Hardware multithreading in computer architecture

In multithreading is the ability of a Where multiprocessing systems include multiple complete processing units in one or more cores, multithreading aims to increase utilization of a single core by using Overview [ ] The multithreading Two major techniques for throughput computing are multithreading and Advantages [ ] If a thread gets a lot of Disadvantages [ ] Multiple threads can interfere with each other when sharing hardware resources such as caches or Overall efficiency varies; From the software standpoint, hardware support for multithreading is more visible to software, requiring more changes to both application programs and operating systems than multiprocessing. Hardware techniques used to support Types of multithreading [ ] Interleaved/Temporal multithreading [ ] Main article: Coarse-grained multithreading [ ] The simplest type of multithreading occurs when one thread runs until it is blocked by an event that normally would create a long-latency stall. Such a stall might be a cache miss that has to access off-chip memory, which might take hundreds of CPU cycles for the data to return. Instead of waiting for the stall to resolve, a threaded processor would switch execution to another thread that was ready to run. Only when the data for the previous thread had arrived, would the previous thread be placed back on the list of For example: • Cycle i: instruction j from thread A is issued. • Cycle i + 1: instruction j + 1 from thread A is issued. • Cycle i + 2: instructi...

Existing superscalar and Very Large Instruction Word (VLIW) microprocessors utilize multiple functional units in order to exploit instruction-level parallelism from a single thread of control flow. These kinds of microprocessors are depending on the compiler or the hardware of the system in order to excerpt instruction-level parallelism from programs and to then afterward schedule independent instructions on multiple functional units on each machine cycle. And when the issue rate of future microprocessors increases, however, the compiler or the hardware will have to extract some more instruction-level parallelism from programs by analyzing a larger instruction buffer (for example -Reservation Station Entry). It is very tough to extract enough parallelism with a single thread of control even for a small number of functional units. Limitation of Single-threaded sequencing mechanism are as follow: • In order to exploit instruction-level parallelism, independent instructions from different-different basic building-blocks in a single instruction stream needed to be examined and issued together. • As the issue rate increases, a larger instruction buffer (for example -Reservation Station Entry) is needed to contain several basic building-blocks, which will be control dependency on different branch conditions, but their examination must be hit together. • And Instruction-level analytical execution with branch prediction is also needed to move independent instructions across basic ...

By • Senior Technology Editor What is a multicore processor? A multicore processor is an integrated circuit that has two or more processor cores attached for enhanced performance and reduced power consumption. These processors also enable more efficient simultaneous processing of multiple tasks, such as with The use of multicore How do multicore processors work? The heart of every processor is an execution engine, also known as a core. The core is designed to process instructions and data according to the direction of software programs in the computer's memory. Over the years, designers found that every new processor design had limits. Numerous technologies were developed to accelerate performance, including the following ones: • Clock speed. One approach was to make the processor's clock faster. The clock is the "drumbeat" used to synchronize the processing of instructions and data through the processing engine. • Hyper-threading. Another approach involved the handling of multiple instruction threads. • More chips. The next step was to add processor chips -- or dies -- to the processor package, which is the physical device that plugs into the motherboard. A dual-core processor includes two separate processor cores. A Multicore processors have multiple processing units incorporated in them. They connect directly with their internal cache, as well as with the system bus and memory. However, multicore chips have several issues to consider. First, the addition of more process...