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138 lines
3.6 KiB
Markdown
138 lines
3.6 KiB
Markdown
---
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title: "04-computer-architecture"
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aliases:
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tags:
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- cosc204
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- lecture
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sr-due: 2022-07-26
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sr-interval: 3
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sr-ease: 250
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---
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- tristate buffer [slide](https://i.imgur.com/2Kb419g.png)
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-  [circuit simulator](https://tinyurl.com/2bmqovqz)
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- 
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# Bus
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- data bus
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- address bus
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- control bus
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- conmmunicate between parts of the computer
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- only one transmitter at a time
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- only addressed device can respond
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- 2 levels
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- internal
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- external
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# Memory
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- memory size is dependent on bus size
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- 2n bytes for n-lines on the address bus
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- 2^8=256B, 2^16=64KB, 2^32=4GB, 2^64=16EB
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- flip flops are grouped into bytes (or larger)
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- each byte has an address
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- to write
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- present the address and the data
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- tell chip to write
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- to read
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- present the address
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- tell the chip to read
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- look at the data
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## Static RAM (SRAM)
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- memory made from flip flops is called static RAM
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- used mostly in CPU cache
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- or anywhere where only a small amount is needed
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- expensive
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## Dynamic RAM (DRAM)
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- made from capacitors
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- used where large amount of RAM is needed
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- slower than SRAM
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- inexpensive
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## Non-Volatile Memory
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- often called ROM (read only memory)
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- can also be called PROM, EPROM, EEPROM, FLASH
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- flash
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- uses floating-gate flash cells, not quite a transistor
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# ALU
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- performs arithmetic
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- add, subtract, etc.
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- logical operations
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- and, or, shift, etc
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- subunits
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- lofical operations
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- addition
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- multiplication and dividion
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- shifting
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- comparison
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- logical tests (if, >0, <0, =0, <=0, etc)
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# Control unit
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- coordinates the operation of the computer
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- generates control signals
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- connect registers to the bus
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- control the function of the ALU
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- provides timing signals to the system
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allso associated with the decoding and executuion of instructions in a pipelined system
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# Registers
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- memory cells with names
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- hold data, instructions, or CPU status
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- various sizes, (8, 16, 32, or 64, or larger (512))
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- hold data typically the same width as memory words
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- registers for accessing memory typically the same with as the address bus
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Special purpose registers
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- program counter
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- stores address of current instruction
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- accumulator
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- source of one of the operands
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- destination of the result
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- status flags
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- individaul bits store information about results of operations
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- result of last instruction was negative, zero, or postive
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- carry from most recent arithmetic operation
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- overflow occurred during the last instruction
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# CPU
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# Computer
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# Instructions
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- bit patterns
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- can be split into a number of fields
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- operation to be executed
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- the address in memory
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- which registers (or memory cells) to use as operands
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- where to place the result (registers or memory)
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# Stored program computer
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# Von Neumann Architecture
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- three key concepts
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- data and instructions are stored in a single read-write memory
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- contents of memory are addressable by location, without regard to the type of data contained
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- execution occurs in a sequential fashion, unless explicitly altered, from one instuction to the next
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- programs and data are the same thing
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- and so its possible to write soure code (data) and comile them into executables (programs) that can be loaded as data and then executed as programs
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# Early computers
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