quartz/content/notes/04-computer-architecture.md

title	aliases	tags
04-computer-architecture		cosc204

• tristate buffer slide
• circuit simulator
• 

Bus

• data bus

• address bus

• control bus

• conmmunicate between parts of the computer

• only one transmitter at a time

• only addressed device can respond

• 2 levels

  • internal
  • external

Memory

• memory size is dependent on bus size

  • 2n bytes for n-lines on the address bus
    • 2^8=256B, 2^16=64KB, 2^32=4GB, 2^64=16EB

• flip flops are grouped into bytes (or larger)

  • each byte has an address
  • to write
    • present the address and the data
    • tell chip to write
  • to read
    • present the address
    • tell the chip to read
    • look at the data

Static RAM (SRAM)

• memory made from flip flops is called static RAM
  • used mostly in CPU cache
  • or anywhere where only a small amount is needed
  • expensive

Dynamic RAM (DRAM)

• made from capacitors
• used where large amount of RAM is needed
• slower than SRAM
• inexpensive

Non-Volatile Memory

• often called ROM (read only memory)
  • can also be called PROM, EPROM, EEPROM, FLASH
• flash
  • uses floating-gate flash cells, not quite a transistor

ALU

• performs arithmetic
  • add, subtract, etc.
• logical operations
  • and, or, shift, etc
• subunits
  • lofical operations
  • addition
  • multiplication and dividion
  • shifting
  • comparison
  • logical tests (if, >0, <0, =0, <=0, etc)