Lecture on Central Process Unit CPU

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Lecture on Central Process Unit (CPU)
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Central Processing Unit

• Brain of any processing device
• What are the processing devices?
• Computers, cell phones, game consoles, TVs,
  refrigerators, just about any electronics
• CPU is a conceptually simple, but a highly
  complex circuitry that responds to executable
  inputs (i.e., program instructions).

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Intel Pentium 4 CPU
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Main Components of CPU

• Control unit Directs all program instructions.
  It does not actually execute instructions, but
  makes other parts to do so.
• Arithmetic logic unit It executes all arithmetic
  and logical operations. Commonly known as ALU.
• Registers Small memory blocks (a few kilo bytes)
  inside CPU to store intermediate computation
  results or addresses during processing
• Caches Larger memory blocks (a few mega bytes)
  inside CPU to store data during processing

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How Does Computer Work?

• Application software is written in a human
  readable form, normally stored in hard disk.
• To run application software, OS retrieves it
  first from hard disk, and translates it to a
  machine readable form. Then, OS instructs CPU how
  to run it.
• CPU interfaces with rest of computing hardware
  and together executes the machine readable code
  from OS.
• Computing hardware is controlled by CPU.

Application Software (Outlook, Safari, iTune)
Operating System (Windows, MacOS)
CPU (Intel, AMD)
Computing Hardware (Dell, IBM, Apple)
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Computing Hardware
CPU
MOTHERBOARD

• CPU Main controller
• Memory All instructions and data are entered
  into CPU through memory
• Input device Keyboard, mouse, touch screen, etc.
• Output device Display terminal, printer, speaker
  etc.
• Hard disk Mass storage for all data, program,
  and information

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Mother of All Boards Motherboard
CPU
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Addressing

• In computer, all storage devices (memories and
  hard disk) are given unique addresses.
• Main memory is fast and can interact with CPU
  directly. But its size is limited (a few giga
  bytes) and cannot store all of the data or
  programs.
• Data or program is loaded into main memory when
  needed by CPU. Otherwise, it is stored in hard
  disk. This process is called swapping.

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What Happens When You Turn on Computer?

• When you turn on the computer, the hardware
  starts.
• With the power on, the CPU starts executing
  instruction at certain memory location. This is
  the BIOS.
• The BIOS contains the start-up programs such as
  device detection, initialize background programs
  (demons), and the start of OS.
• Critical part of OS (i.e., part needed by all
  programs) is permanently loaded into the main
  memory. This part is called the kernel.
• Now the computer is ready to accept any command
  that the user enters.

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Scheduling Queues

• Scheduling queues is a main functions of OS.
• Job queue Set of all processes
• Ready queue Set of all processes residing in
  main memory, ready and waiting to execute
• Device queue Set of processes waiting for I/O
  device

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Interactions with Memory

Memory
CPU
Address Lines
Data Lines
Read Line
Write Line
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CPU Execution Cycle
Obtain instruction from program storage
Determine required actions and instruction size
Locate and obtain operand data
Compute result value or status
Deposit results in storage for later use
Determine successor instruction can generally be
combined w/ Decode
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Thread

• Thread Schedulable stream of controls
• Defined by CPU
• Suspend Save register values in memory
• Resume Restore registers from memory
• Multiple threads can execute independently
• They can run in parallel on multiple CPUs...
• Or interleaved on a single CPU
• Each thread must have its own control stack.

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Single and Multithreaded Processes
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Two Threads Sharing a CPU
concept
reality
context switch
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Speed

• How fast the CPU can execute instructions
• Limited by many factors
• Speed of electronic circuits in CPU
• Speed of memory access
• Speed of hard disk
• Efficiency of OS
• Efficiency of application software

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Processor Speed
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CPU

• high speed

slower I/O devices
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PCI Bus

• Peripheral Connection Interface
• South Bridge architecture
• 66 MHz, 64-bit, 512 MB/second
• Shared bus with arbitration

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PCI Express

• North Bridge architecture
• Switched, point-to-point connection
• Data rate up to 4 GB/second

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