Hardware and Virtual Machines

Question 1

Characteristics of Massively Parallel Computers

Answer 1

-It is a large number of computer processors / separate computers connected together
…where they are simultaneously performing a set of coordinated computations // collaborative processing.
-Network infrastructure
-Communicate using a message interface.

Question 2

Characteristics of CISC (Complex Instruction set computers)

Answer 2

-Uses many instruction formats.
-Uses variable length instructions.
-Makes use of different addressing modes.
-Uses a few registers
-Has a large instruction set.
-Requires complex circuits.
-Frequently uses cache.
-Instructions (converted to sub-instructions that) may require many clock cycles –Programmable CU

Question 3

Characteristics of RISC (Reduced Instruction set computers)

Answer 3

-Uses simple instructions.
-Uses fixed length instructions.
-Instructions only require one clock cycle.
-Uses many registers.
-Makes use of pipelining
-Hardwired CU

Question 4

Describe the use of pipelining in RISC

Answer 4

-Pipelining allows several instructions to be processed simultaneously.
…therefore this increases the number of instructions completed per unit of time.
-Each instruction stage is completed during one clock cycle.
-No two instructions can execute their same stage of instruction.
-E.g. While one instruction is coded the next is being fetched.

Question 5

What are the 4 computer architectures.

Answer 5

-SISD (Single Instruction Single Data)
-SIMD (Single Instruction Multiple Data)
-MISD
-MIMD

Question 6

Explain what is meant by a virtual machine.

Answer 6

-The emulation of a computer system / hardware and/or software
… using a host computer system.
-Using guest operating system(s) for emulation.

Question 7

What are the benefits of using a virtual machine.

Answer 7

-Multiple guest operating systems / VMs can be used on the same computer.
-Different instruction set architectures can be emulated on a single computer.
- A virtual machine can crash without affecting the host machine.
There are security benefits // Trying a piece of suspicious software and if it is / has a virus, it will only infect the virtual machine.
-Cost savings due to not needing to purchase extra hardware.
-Can run legacy applications that are currently incompatible.

Question 8

Limitations of a virtualmachine.

Answer 8

-Using a virtual machine means execution of extra code….
-Non-VM installation may not perform in the same way.
-Execution speed slower than non-VM system.
-Problems in judging actual response times at time of maximum traffic needs fastest possible speed.
-Particular hardware may be difficult to emulate . So that hardware can’t be tested using a virtual machine.
- A virtual machine may be affected by any weaknesses of the host machine.
-Costly and/or complex to maintain / implement / manage

Question 9

What is the use of virtual machine software (hypervisor)?

Answer 9

It is used to:
-Create/delete virtual machines.
-Existing hardware made available to guest OS // hardware emulation
-Ensures each virtual machine is protected from actions of another virtual machine.

Question 10

What does the Host OS do? (topic virtual machines)

Answer 10

-The operating system that is actually controlling the hardware

Question 11

What does the Guest OS do? (topic virtual machines)

Answer 11

-An operating system run on the virtual machine //OS is being emulated
-Guest OS runs under the host OS

Question 12

Describe how interrupts are handled in pipelining

Answer 12

-Once the processor detects the existence of an interrupt.
-To discard all instructions in the pipelining except for the last instruction in the writeback stage.

Question 13

Explain what is meant by pipelining.

Answer 13

-Pipelining is instruction level parallelism.
-Execution of an instruction is split into a number of stages.
-When the first stage for an instruction is completed, the first stage of the next instruction can start executing.
-Another instruction can start executing before the previous one is finished.
-Processing a number of instructions can be concurrent/simultaneous.

Question 14

Explain what is meant by SISD.

Answer 14

-There is only one processor.
-The processor executes one set of instructions on one set of data.

Question 15

Explain what is meant by SIMD, MISD, MIMD.

Answer 15

-Many processors execute the same instruction using different data sets.
-Many processors execute different instructions using the same data set.
-Many processors execute different instructions using different data sets.

Question 16

Changes needed for codes in order to run on massively paralleled computers

Answer 16

-Split into blocks of code.
… that can be processed simultaneously
… instead of sequentially.
-Each block is processed by a different processor.
-Which allows each of many processors to process the different blocks of code independently.
-Requires both parallelism and coordination.

Question 17

Explain one of the hardware issues that will be overcome if a massively parallel computer is to function correctly

Answer 17

-Communication between processors is the issue.
-Each processor needs a link to other processors.
-Many processors require many of these links.
-Challenging topology.

Question 18

A computer has a single processor that contains four processing units. Explain why this is not an example of a massively parallel computer:

Answer 18

-Only one separate processor
-Quad core computer system // processing unit shares the same bus.

Question 19

Identify different types of parallelism

Answer 19

-Instruction
-Processor
-Memory usage
-Computer system.

Question 20

Describe what happens after the guest operating system has received the data request from the application.

Answer 20

-Guest OS handles the request as if it were running on its own physical machine.
-Guest OS handles the request as usual.
-I/O requests are translated by the virtual machine software.
-Into instructions executable by the host OS
-Host OS retrieves the data from the file.
-Host OS passes the data into virtual machine software
-The virtual machine passes the data to the guest OS.
-Guest OS passes the data to the application.