[15] HARDWARE AND VIRTUAL MACHINES

• Description of RISC

  · Simple instructions

  · Fixed length instructions

  · Uses many registers

  · Makes use of pipelining

  · Less complex circuits

  · Single cycle instructions

  · Few instruction formats
• Description of CISC

  · Many instruction formats · Complex instructions · Variable length instructions · Few registers · Large instruction set · Requires complex circuits · Poor pipeline ability
• Differences between RISC + CISC

  · CISC more instructions · CISC fewer registers · CISC more complex instructions · CISC more instruction formats · CISC variable length instructions · CISC worse pipelineability
• Benefits of virtual machine

  Multiple guest operating systems can be used on the same computer with the use of multiple virtual machines

  Can be used to test new operating system versions as if the guest OS crashes the host hardware remains unaffected

  Can be used to run legacy software which cannot be run on newer hardware
• Limitations of virtual machine

  Virtual machines are expensive to maintain

  Virtual machines has poorer performance than real machines because of the extra load on host computer

  Unable to emulate some hardware
• SISD

  one processor executes same instruction using the same data set one instruction applied to one data set
• SIMD

  many processors execute same instruction using different data sets
• MISD

  many processors execute different instructions using the same data set
• MIMD

  Many processors executing different instructions using different data sets
• Process of pipelining

  · Instructions divided into subtask · Each subtask completed during 1 clock cycle · Only 1 instruction is completed during 1 cycle · Second instruction begins in second clock cycle, when first instruction moved on to second subtask
• Description of virtual machine

  · Emulation of computer hardware and/or software · Using host computer system · Uses guest OS for emulation
• Pipelining

  Instruction level parallelism

  Overlapping multiple instructions

  More instructions executed in shorter period of time
• Role of a virtual machine

  · Provide a safe environment during testing · Trial/use alternative replacement operating system(s) · Provide additional services – trial a print server
• characteristics of massively parallel computers

  · Large number of processors · Working together simultaneously + collaboratively · Communicate using message interface
• Purpose of E & F

  Purpose of E = Sum Purpose of F = Carry
• Purpose of a sr flip flop

  acts as data storage

  store a binary bit
• extra input in JK flip flop

  clock
• advantage of JK flip flop

  invalid state cannot occur
• Massively parallel computers

  Large number of processors working collaboratively and simultaneously on same program communicating via a message interface