UNIT
– V ADVANCED COMPUTER ARCHITECTURE
1. What is the Multithreading?
Multithreading allows multiple threads to share the functional units of a single processor in an overlapping fashion. To permit the sharing, the processor must duplicate the independent state of each thread.
2. What do you mean by implicit multithreading?
Implicit multithreading refers to the concurrent execution of multiple threads extracted from a single sequential program.
3. Define interleaved or fine-grained multithreading?
Interleaved multithreading is a version of hardware multithreading that suggests switching between threads after every instruction.
4. What is coarse grained multithreading?
It switches threads only on costly stalls. Thus it is much less likely to slow down the execution an individual thread.
5. What do you mean by explicit multithreading?
Explicit multithreading refers to the concurrent execution of instructions from different explicit threads, either by interleaving instructions from different threads on shared pipelines or by parallel execution on parallel pipelines.
6. What do you mean by implicit multithreading?
Implicit multithreading refers to the concurrent execution of multiple threads extracted from a single sequential program.
7. What is the FLYNN’s classification of Multiprocessors?
Multiprocessor is used to increase performance and improve availability. The different categories are SISD, SIMD, MISD and MIMD.
8. What are two main approaches to multithreading?
• Fine – grained multithreading
• Course – grained multithreading
9. Write the advantages of Multithreading.
If a thread gets a lot of cache misses, the other thread(s) can continue, taking advantage of the unused computing resources, which thus can lead to faster overall execution, as these resources would have been idle if only a single thread executed. If a thread cannot use all the computing resources of the CPU (because instructions depend on each other’s result), running another thread permits to not leave these idle. If several threads work on the same set of data, they can actually share their cache, leading to better cache usage or synchronization on its value.
10. List the major MIMD styles.
Multiple control units and multiple processing elements are organized such that multiple processing elements handle multiple data streams. The processors work on their own data with their own instructions.
11. Distinguish between shared memory multiprocessor and message – passing multiprocessor.
In shared memory multiprocessor a single address space is used by all processors. The processors communicate by writing on or reading from the common shared memory using load and store instructions.
In message passing multiprocessor system each processor has its own large memory and there will be multiple address spaces. Communication of data is done by passing messages among processors.
12. What is multicore? Or what is CMT?
Multi – core is a design in which a many processors are packaged in a single unit to form a single physical processor. The goal of this design is to enable a system to run more tasks simultaneously and thereby achieve greater overall system performance. Multicore processors are also called as Chip Multiprocessors (CMP) and the technology is known as chip multiprocessor technology (CMT). They are now the only way to build high performance microprocessors, for a variety of reasons.
13. What is the need for multicore processors?
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. In addition, one cannot simply ratchet up the clock speed on today’s processors, or the power dissipation will become prohibitive in all but water – cooled systems.
14. Write the software implications of a multicore processor?
Multi-core systems will deliver benefits to all software but especially multi-threaded programs. All code that supports high performance computing or multiple processors technology will benefit automatically from multi-core processors without need for modification. Most server-side enterprise packages and many desktop productivity tools fall into this category.
15. What is meant by hardware multithreading?
It switches threads only on costly stalls. Thus it is much less likely to slow down the execution an individual thread.
16. Mention any four types of Multiprocessor Network topologies
The network topologies are, Ring topology, cross bar, omega network, mesh or grid topology and n-cube tree topology.
17. What is cluster?
Cluster is a collection of computers connected via standard network switches to form message passing networks
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