1
Q
Virtual Machine
A
- using software to implement emulation.
- An emulation of computer system or software
- Using a host computer system
- Using guest OS for emulation
2
Q
VM drawback
A
- execution of extra code
- Performance degrades
- Cannot make judgements about response time
- May not be able to emulate hardware, the hardware exists before VM is created
- A virtual machine may be affected by any weaknesses of host machine
2
Q
VM benefit
A
- allow multiple guest OS to run on one computer using host OS
- multiple OS exists simultaneously
- Allowing testing using same hardware
- Only require one set of hardware
- Reduce cost
- Easier to recover if software emulating new computer causing system crash
- VM protects other software
2
Q
Role of Virtual Machine software?
A
- create/delete/manage VM
- Protect VM
- Translate guest OS instruction to the one used by host OS
- Hardware emulation
3
Q
Host OS vs Guest OS
A
- guest OS is OS running in VM, host OS is running VM software
- Host OS controls the physical hardware, guest OS controls virtual hardware - Guest
OS run under Host OS
4
Q
Differences RISC and CISC
A
5
Q
Pipelining
A
- Instruction fetch
- Instruction decode
- Operand fetch
- Instruction execution
- Write back result
6
Q
Characteristics of Massively parallel computer
A
- Massively: Large number of processors
- Parallel: perform a set of coordinated computations simultaneously
- Network infrastructure
- work collaboratively on same program
- Work together simultaneously on same program
- Communicating via a messaging interface
7
Q
How to update single computer to make use of massively parallel computer ?
A
- split into blocks of code
- Instead of sequentially
- Each process processed by a different processor
- Which allows each of many processors to simultaneously process different blocks of code independently
8
Q
Hardware issues of massively parallel computer
A
- Communication between different processors is the issue
- Each processor needs a link to every other processor
- Many processors require many of this links
- Challenging topology
9
Q
Software issues of massively parallel computer
A
- suitable program needed to allow data to be processed simultaneously by multiple processors
10
Q
Define pipelining
A
- instruction level parallelism
- Processing of a number of instructions can be simultaneous
- After 1st stage of an instruction is competed, 1st stage of the next instruction can start
executing - Another instruction can start executing before previous one is finished
11
Q
Pipelining process
A
- instruction divided to 5 stages
- Instruction fetch, instruction decode, operand fetch, instruction execute, write back result.
- Each subtask is completed in one clock cycle
- No two instruction can executes same stage at the same clock cycle
- Second instruction begin in second clock cycle, while the first instruction has moved on to its second
subtask.
12
Q
MISD
A
- several processor
- Different instructions
- One set of data
13
Q
SIMD
A
- processor has several ALU
- ALU executes same instruction
- Different data
14
Q
SISD
A
- one processor
- One instruction
- One data
- Process instructions sequentially
15
Q
MIMD
A
- several processor
- Different instruction
- Different data
16
Q
Why cannot S=0 & R=0 or S=1 & R=1
A
- Q and not Q are the same
- Must be complement with each other
- Become unstable
17
Q
Why JK flip-flop is an improvement on SR flip-flop
A
- SR flip-flop allows Q & not Q to have same value.
- JK flip-flop does not allow Q & notQ to have same value.
- Unstable state avoided
- All 4 combinations are valid
- SR’s input may not arrive at the same time
- JK has a clock pulse to synchronise inputs
18
Q
JK flip-flop consists of
A
- Set
- Reset
- Clock (pulse)
19
Q
Role of flip-flops in a computer
A
- a flip-flop can store either a 0 or a 1.
- Computers use bits to store data
- Flip-flop can therefore be used to store bits of data
- Memory can be created from flip-flops
20
Q
When guest OS received data request from the application ?
A
- Guest OS handles request as if it is running on its physical hardware
- Guest OS handles requests as usual.
- I/O requests are translated by VM software
- Into instructions used by host OS.
- Host OS retrieves data from the file
- Host OS passes data to VM software
- VM software passes data to guest OS
- Guest OS passes data to the application.
21
Q
Benefits of K-map
A
- minimise boolean expression, no need to use various boolean expression
- Minimise number of logic gates used to solve an logic expression, reduce errors
