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43 Cards in this Set
- Front
- Back
What are the basic components of a microcomputer?
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CPU (central processor unit), memory storage unit, i/o devices, data bus, control bus, and address bus
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What are the components in the CPU?
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registers, ALU, control unit, and clock
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What are registers?
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temporary storage locations for processing
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What is the purpose of the clock?
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heartbeat of the system -- to synchronize the internal operations of the CPU with other system components
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What is the purpose of the control unit?
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to coordinate the sequencing of steps involved in executing machine instructions
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What is the purpose of the ALU?
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to perform arithmetic operations such as addition and subtraction and logical operations such as AND, OR, and NOT
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what is a bus?
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a group of parallel wires that transfer data from one part of the computer to another.
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what are the three types of buses?
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data bus, control bus, and address bus
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describe the data bus.
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transfers instructions and data between the CPU and memory (or CPU and i/o devices). BI-DIRECTIONAL (send & receive)
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describe the control bus.
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uses binary signals to synchronize actions of all devices attached to the system. Determines whether the CPU will read or write
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describe the address bus
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holds the addresses of instructions and data when the currently executing instruction transfers data between the CPU and memory. UNI-DIRECTIONAL (only sends from CPU)
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what is the clock?
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the synchronization of each operation involving the CPU and system bus, pulsing at a constant rate. The clock also triggers events.
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what is the basic unit of time for machine instructions?
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a machine cycle (or clock cycle)
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what is the length of a clock cycle?
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the time required for one complete clock pulse
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how is the duration of a clock cycle calculated?
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1/(clock speed), measured in oscillations per second (Hertz)
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if read = 0 and write = 1, what is the CPU doing?
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reading
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if read = 1 and write = 0, what is the CPU doing?
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writing
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if read = 1 and write = 1, what is the CPU doing?
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wait servicing
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if read = 0 and write = 0, what is the CPU doing?
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this is illegal and will never happen!
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what is the order of the instruction execution cycle?
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fetch, decode, fetch operands, execute, store output
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what is the process to read from memory?
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1. address placed on address bus
2. read line set low (read = 0) 3. CPU waits one cycle for memory to respond 4. read line goes to 1 (read = 1), indicating the data is on the data bus |
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What are the named storage locations inside the CPU?
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(32-bit:) EAX, EBX, ECX, EDX, EBP, ESP, ESI, EDI, EFLAGS, EIP, (16-bit:) CS, SS, DS, ES, FS, GS
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Which registers can you access parts of? (8-bit & 16-bit)
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EAX, EBX, ECX, EDX
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What is the naming convention for the 8-bit and 16-bit registers for ExX registries?
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16-bit: xX, 8-bit: xL & xH (H indicating higher and L indicating lower)
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Which registers can you access the full 32-bit or the lower 16-bit?
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ESI, EDI, EBP, ESP
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What is the naming convention for the 16-bit registers for ESI, EDI, EBP, and ESP?
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the last 2 letters (SI, DI, BP, SP)
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what do ESP and EBP do?
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manage the stack
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what do ESI and EDI do?
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index addressing
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to multiply or divide, which registry should be used?
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EAX
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which registry is used as a loop counter?
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ECX
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what are the purposes of the 16-bit registries: CS, SS, DS, ES, FS, GS?
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CS: code segment, SS: stack segment, DS: data segment; ES, FS, GS: additional segments
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what is the purpose of the EIP registry?
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instruction pointer (points to next set of instructions)
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what is the purpose of the EFLAGS registry?
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status and control flags (each flag is a binary bit)
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a flag is set when it equals what?
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1
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a flag is clear (or reset) when it equals what?
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0
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When is the carry flag set?
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(CF) is set when the result of an UNSIGNED arithmetic operation is too large for it into the destination
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When is the overflow flag set?
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(OF) is set when the result of a SIGNED arithmetic operation is too large or too small to fit into the destination
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When is the sign flag set?
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(SF) is set when the result of an arithmetic or logical operation generates a negative result
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When is the zero flag set?
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(ZF) is set when the result of an arithmetic or logical operation generates a result of zero
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When is the auxillary flag set?
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(AC) is set when an arithmetic operation causes a carry from bit 3 to bit 4 in an 8-bit operand
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When is the parity flag set?
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(PF) is set if the least-significant bye in the result contains an even number of 1 bits. Otherwise, PF is clear (used for error checking when there is a possibility that data might be altered or corrupted)
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What is indirect addressing?
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moving the contents (ref by variable) into new location
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What is direct addressing?
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moving a value (such as 23h) into new location
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