NT1110 Unit 6 Assignment 1
November 14, 2014
Video Summery 1.08 Memory
There are two types of memory ROM (read only memory) and RAM (random access memory). There are two types of RAM: DRAM and SRAM. DRAM aka dynamic random access memory, is the most common but not as fast. SRAM aka static random access memory, is much faster than DRAM in terms of speed, but is not purchased as often because of its price. There are three types of DRAM; SIMM, DIMM, and RIMM. SIMM were used in older model computers. They ran on a 32-bit data path and could either be 30 or 72-pin. The 30-pin was smaller with no notch and the 72-pin had a single notch offset from the center. DIMM has a 64-bit data path. Today’s DIMM is known as SDRAM or synchronous dynamic RAM. It comes in either DDR SDRAM (double data rate) or DDR2 SDRAM (double data rate 2). The original SDRAM had 168 pins and two notches for alignment. DDR SDRAM had 184 pins, one notch for alignment, and is two times faster than SDRAM. The DDR2 SDRAM has 240 pins, one notch for alignment and is four times faster than SDRAM. Both DDR and DDR2 SDRAM use duel channeling technology meaning that two slots process information together faster. RIMM is known as RAMBUS or RDRAM. It is similar in appearance to DIMM. It has two notches in the center for alignment. It is faster but more expensive. Thought to replace SDRAM but DDR and DDR2 dominates it today.
To check for memory errors in older computers it used technology called parity bit which checked the integrity of each byte. It determined if byte was good or bad but not which bit and cannot repair any errors. Today we use something called ECC. It can check bits and repair