Memory organization Flashcards
bit
smallest unit of binary data
byte
8-bit unit
nibbles.
4-bit unit
word
generally, consists of one or more bytes
address
The location of a unit of data in a memory array
two types of memories
Random-Access Memory (RAM),
Read-Only Memory (ROM).
RAM (random-access memory)
is a type of memory in which all addresses are accessible in an equal amount of time and can be selected in any order for a read or
write operation.
ROM (read-only memory)
is a type of memory in which data are stored
permanently or semi permanently
categories of RAM
static RAM (SRAM) and the dynamic
RAM (DRAM)
Static RAMs
generally use flip-flops as storage elements and can,
therefore, store data indefinitely as long as dc power is applied
Dynamic RAMs
It use capacitors as storage elements and cannot retain data very long without the
capacitors being recharged by a process called refreshing.
Comparison between SRAM and DRAM
It consists of a number of flipflops.
Each flip-flop stores one bit.
It stores the data as a charge on the capacitor. It consists of MOSFET and capacitor for each cell.
2
Its access time is less, hence, it is
faster
Its access time is greater than static RAM, hence, it is slower memory
3
It contains less memory cells per unit area. Hence, it is less dense than DRAM.
It contains more memory cells per unit area. Hence, it is denser than SRAM.
4
Refreshing circuitry is not required.
Refreshing circuitry is required to maintain the charge on the capacitors every time after every few milliseconds.
5
It is more expensive than DRAM
It is more expensive than DRAM
6
Power Consumption is lower
Power Consumption is higher
7
Used in cache memory
Used in main memory
8
Occupies more space
Occupies less space
SRAM
DRAM
Types of DRAMs
Synchronous DRAM (SDRAM)
Double Data Rate SDRAM (DDR SDRAM)
Double Data Rate SDRAM (DDR SDRAM)
This memory nearly doubles the bandwidth of a single data rate (SDR) SDRAM
Synchronous DRAM (SDRAM)
The SDRAM synchronizes the speed of the memory along with the CPU clock speed
