EE4455: Tutorial 3 1. Survey the differences between fixed-function ...

The vector instruction generally operates on longer sets of inputs. It canalso operate on longer operands. The vector unit may require specializedregisters and may require more time to fill and empty the pipeline.3. Identify possible instructions in matrix multiplication.Answer:Matrix multiplication is of the form:for (i=0; i

4. What are the differences between VLIW and Superscalar?Answer:Both VLIW and Superscalar architectures can improve the speed ofexecution in a processor.In a superscalar processor, it exploits what is called Instruction Levelparallelism (ILP). It takes a bunch of instructions and loads them all atonce. These instructions are taken out of a window of instructions,typically a window of about 16 instructions (issue window, reservationstations). Having a larger window means we have a larger scope fromwhich the processor will try to find independent instructions, andexecute them as soon as possible. Now however, the register file getsmuch bigger (since we now need more registers to be able to do morethings in parallel).In VLIW processor, we do not try to do all the figuring out on the fly inhardware. The processor is now a lot simpler, and the complexity ismoved to the compiler. Now instead of having 4 separate instructionswith dependences, the compiler arranges the program so that the

instructions sent to the processor are bundles (single instructions)containing, say 4 independent operations, which are fetched at the sametime, and executed at the same time etc. The compiler now determineswhat has to be done in parallel.5. What are the differences among these terms: multitasking andmultithread and multiprocessing?Answer:Multitasking is running multiple "heavyweight" processes (tasks) by asingle OS. In computing, multitasking is a method by which multipletasks, also known as processes, share common processing resources suchas a CPU. With a multitasking OS, such as Windows XP, you cansimultaneously run multiple applications. Multitasking refers to theability of the OS to quickly switch between each computing task to givethe impression the different applications are executing multiple actionssimultaneously.Multithreading is running multiple "lightweight" processes (threads ofexecution) in a single process / task / program. Multithreading extends

the idea of multitasking into applications, so you can subdivide specificoperations within a single application into individual threads. Each ofthe threads can run in parallel. The OS divides processing time not onlyamong different applications, but also among each thread within anapplication.Multiprogramming is essentially a synonym for multitasking (thoughmultitasking connotes sharing more resources than just the CPU, and isthe more popular term).Multiprocessing involves using multiple CPUs, either in the same(SMP) or different (MPP) host boxes, to run a program. When runningon a multicore system, multitasking OSs can truly execute multiple tasksconcurrently. The multiple computing engines work independently ondifferent tasks.

6. Differences between von-Neumann, Harvard, and modifiedHarvard architecture. Give some examples.Answer:A von Neumann architecture defines a single memory space to storeinstructions and data. An Harvard architecture defines separate memoryspaces for instructions and data; separate data and instruction busesallow simultaneous fetches and transfers to occur. Real-world examplesof Harvard-based processor designs include ARM’s ARM9/ARM10,MPC860, 8031, and DSPs, whereas ARM’s ARM7 and x86 are vonNeumann-based designs.A modified Harvard architecture machine is very much like a Harvardarchitecture machine, but it relaxes the strict separation between

instruction and data, while still letting the CPU concurrently access two(or more) memory buses. One type of modified Harvard modificationprovides a pathway between the instruction memory (such as ROM orflash) and the CPU to allow words from the instruction memory to betreated as read-only data.