19-04-2012, 05:02 PM
Computer Organization
08-CompOrg.ppt (Size: 103 KB / Downloads: 54)
Computer design as an application of digital logic design procedures
Computer = processing unit + memory system
Processing unit = control + datapath
Control = finite state machine
Inputs = machine instruction, datapath conditions
Outputs = register transfer control signals, ALU operation codes
Instruction interpretation = instruction fetch, decode, execute
Datapath = functional units + registers
Functional units = ALU, multipliers, dividers, etc.
Registers = program counter, shifters, storage registers
Memories
Larger Collections of Storage Elements
Implemented not as FFs but as much more efficient latches
High-density memories use 1-5 switches (transitors) per bit
Static RAM – 1024 words each 4 bits wide
Once written, memory holds forever (not true for denser dynamic RAM)
Address lines to select word (10 lines for 1024 words)
Read enable
Same as output enable
Often called chip select
Permits connection of manychips into larger array
Write enable (same as load enable)
Bi-directional data lines
output when reading, input when writing
Data Path (Memory Interface)
Memory
Separate data and instruction memory (Harvard architecture)
Two address busses, two data busses
Single combined memory (Princeton architecture)
Single address bus, single data bus
Separate memory
ALU output goes to data memory input
Register input from data memory output
Data memory address from instruction register
Instruction register from instruction memory output
Instruction memory address from program counter
Single memory
Address from PC or IR
Memory output to instruction and data registers
Memory input from ALU output