Comp Orgs Final

  • CRC(shows if there is an error not how to fix it):

    • How many bits in CRC

      • (CRC-8) → 9 bits etc.

    • How many bits in checksum

      • count how many chars is the Generator Polynomial starting at 0 so total #-1. ADD that # of 0’s to the end of XOR division

    • How to get checksum/ What you do with checksum

      • XOR division if first digit 0 divide by 000000 instead of GP. APPREND outcome to end of original message

    • What to do on the receiving end

      • Divide message by GP is remained from this is zero, no error in transmission

      • If the remainder is not 0, error, resend

    • all 0’s— no error

  • Marie, simplified computer model:

    • Overview:

      • Binary, twos comp data representation

      • stored program, fixed word data length and instructions

      • 4K words of word-addressable main memory

      • 16-bit data words

    • instruction model looks like

      • 16-bit instructions 4 for opcode 12 for memory address


      • Consists of a smaller sequence of smaller instructions called micro-operations

    • direct vs. indirect addressing

      Direct Addressing

      Indirect Addressing

      contains effective address of operand

      contains reference of effective address.

      one memory reference

      two memory references

      faster processing

      slower processing

      smaller amount of address space

      larger amount of address space

      where the address of the data s given in the instructions

      gives the address of the data in the instruction

      • often useful such as: referencing memory locations large that operand limit of the a CPU and flexibility in addressing

    • 7 different registers for Marie

      1. Accumulator, AC, a 16-bit register that holds a conditional operator (ex. “less than”) or one operand of a two-operand instruction

      2. Memory address register, MAR, a 12-bit register that holds the memory address of an instruction or the operand of an instruction

      3. Memory buffer register, MBR, a 16-bit register that holds the data after its retrieval form, or before its placement in memory

      4. Program counter, PC, a 12 bit register that holds the address of the next program instructions to be executed

      5. Instruction register, IR, which holds an instruction immediately proceeding its execution

      6. Input register, InREG, an 8-bit register that holds data read from an input device

      7. Out register, OutREG, an 8-bit register, that holds data that is ready for the output device

    • what different instructions look like


    Followed by 12 bit memory address

  • Misc.:

    • Simple assembly language program and what it will do (not write, tell what it does)

    • Know at least 5 differences between RISC(Reduced Instruction Set Computer) vs CISC(Complex Instruction Set Computer) computers

      1. RISC has more limited number of instructions while CISC has a large number of instructions

      2. RISC instructions are only capable of performing a single operation while CISC can carry out complex instructions with multiple internal operations

      3. RISC machine logic is simple to decode unlike CISC processors

      4. RISC focuses more on software to execute instructions while CISC focuses on hardware

      5. RISC are embedded with hardwired programming units while CISC are installed with microprogramming unit

      6. RISC uses register to register mechanism to execute while CISC uses memory to memory framework to execute

    • Look at a C simple program and explain what it does (we don’t have to right out own)