Transcript 7. Memory (RAM,ROM)

Computer Architecture
CST 250
MEMORY ARCHITECTURE
Prepared by:Omar Hirzallah
Contents
CPU & Main Memory Architecture
RAM & Types
Comparison
CMOS
ROM & Types
CPU & Main Memory Architecture (Von Neuman)
Data Bus
Processor
C.U.
A.L.U.
R
O
M
R
A
M
Address Bus
Control Bus
Input /
Output
RAM
RAM = RWM.
Random Access Memory, it means,
to access the memory location in the
entire memory is very easy and fast.
 RAM is used for temporary storage of
program and data.
It is volatile so it will lose the data if the
power is turned off.
You can W/R from it with equal ease.
Comparison of DRAM & SRAM
DRAM
SRAM
Data will be lost as the power shuts
down, or capacitor loses its charge.
Data will be lost as the circuits get
powered down.
It needs refreshing from time to time
to keep its contents.
Refreshing, not required.
It is composed of Capacitors &
Transistors.
It is composed of transistors and
resistors.
Slower than SRAM.
Faster than DRAM as no refreshing
is required.
It takes less space on a chip as
compared to SRAM memory cell.
It has more parts so SRAM cell takes
more place on chip then DRAM cell.
Cheaper than SRAM.
Expansive than DRAM.
It is used for Main Memory.
It is used for Cache Memory.
Types of DRAM
1. SDRAM: Synchronous DRAM
 It is a type of DRAM that can run at much higher
clock speeds than conventional memory.
 SDRAM actually synchronizes itself with the CPU's
bus and is capable of running at 133 MHz,
 About twice as fast EDO DRAM.
 SDRAM is replacing EDO DRAM in many newer
computers
 SDRAM usually comes in DIMM packaging, which
itself comes in several different formats (buffered and
un-buffered, 3.3 volts and 5 volts).
2. DDR: Double Data Rate SDRAM
 DDR SDRAM is similar in function to regular SDRAM,
but doubles the bandwidth of the memory by
transferring data twice per cycle--on both the rising
and falling edges of the clock signal.
3. RDRAM Direct Rambus DRAM
 a high-speed 16-bit bus running at a clock rate of 400
MHz
 As with DDR SDRAM, transfers are accomplished on
the rising and falling edges of the clock, yielding an
effective theoretical bandwidth of approximately
1.6 G.bytes/second (DRAM)
 Used with Intel PIII and P4.
CMOS: complementary metal oxide
semiconductor
CMOS chips require less power than chips
using just one type of transistor. This
makes them particularly attractive for use
in battery-powered devices, such as
portable computers. Personal computers
also contain a small amount of batterypowered CMOS memory to hold the date,
time, and system setup parameters.
ROM & ITS Types:
ROM  (READ ONLY MEMORY) It is an integrated circuit that
is programmed with specific instructions at the time of its
manufacturing. It is also known as “FIRMWARE”. Firmware
means that it’s a hardware component along with built in
software stored on it.
1: PROM  Programmable Read Only Memory:
It has a special device for its burning named PROM
Programmer, but It can be burned only once.
2: EPROM  Erasable Programmable Read Only Memory:
It can be erased by using Ultra violet light rays.
3: FLASH MEMORY OR EEPROM  Electronically Erasable
Programmable Read Only Memory: It can be erased
electronically for burning again, e.g. BIOS, CMOS etc.
BIOS stands for BASIC INPUT OUTPUT SYSTEMS