Computer Architecture CST 250 MEMORY ARCHITECTURE Prepared by

Computer Architecture CST 250 MEMORY ARCHITECTURE Prepared by: Omar Hirzallah

Contents l CPU & Main Memory Architecture l RAM & Types l Comparison l CMOS l 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 l RAM = RWM. l Random Access Memory, it means, to access the memory location in the entire memory is very easy and fast. l RAM is used for temporary storage of program and data. l It is volatile so it will lose the data if the power is turned off. l 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 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 l It is a type of DRAM that can run at much higher clock speeds than conventional memory. l SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 133 MHz, l About twice as fast EDO DRAM. l SDRAM is replacing EDO DRAM in many newer computers l 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 l 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 l a high-speed 16 -bit bus running at a clock rate of 400 MHz l 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) l Used with Intel PIII and P 4.

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