Memory

Sizes

• 1 byte = 8 bits
• 1 word: multiples of bytes, is the unit of transfer between main memory and registers, usually the size of a register
• 1kb is $2^{10}$ bytes
• 1mb is $2^{20}$ bytes
• 1gb is $2^{30}$ bytes
• 1tb is $2^{40}$ bytes

Operations

• Read
  • Transfer the address of the desired word to the address lines
• Write
  • Transfers the address of the desired word to address lines AND
  • Transfers data bits (the word) to be stored to the data input lines

EN	Read/Write	Operation
0	X	None
1	0	Write
1	1	Read

RAM

• Static RAM: uses flipflops as memory cells
• Dynamic RAM: uses capacitors to represent data. Simpler, but need to constantly refresh

SRAM cell logic and block diagram

Memory Arrays

Logic construction of 4x3 RAM

Memory array (4k x 8) made of four 1k x 8-bit RAM chips: this can be extended to larger size