RAM
RAM means RANDOM ACCESS MEMORY. It is also called READ/WRITE memory.Information can be read from a RAM and can also be written to it.
It stores the data temporarily. When system shut down means the memorywill be lost.
There are two types of RAM:
1. Static Ram (SRAM)
2. Dynamic Ram (DRAM)
Static Ram (SRAM):
4 bit Static RAM
Earliest 8k Static Ram
Static Ram is a type of RAM it don't require external refresh circuitry or other work in order for them to keep their data intact.
- It is faster than DRAM.
- It take more space than DRAM.
- It is several times expensive than DRAM.
Dynamic Ram is a type of RAM that stores each bit of data in a separate capacitior with an integrated circuit. Many hundreds of times each second, this circuitry reads the contents of each memory cell, whether the memory cell is being used at that time by the computer or not.This refreshing action is why the memory is called dynamic.
To build a 64 MB core memory from SRAMs would be very expensive. The overhead of the refresh circuit is tolerated in order to allow the use of large amounts of inexpensive, compact memory. The refresh circuitry itself is almost never a problem; many years of using DRAM has caused the design of these circuits to be all but perfected.
DRAMs are smaller and less expensive than SRAMs because SRAMs are made from four to six transistors (or more) per bit, DRAMs use only one, plus a capacitor.
Types of Dynamic Ram
- FPM DRAM
- EDO DRAM
- SDRAM
- DDR SDRAM
- DRDRAM
- FPM DRAM – Fast Page Mode Dynamic Random Access Memory is one of the earlier forms of RAM type and is an improvement over the conventional DRAM. Ironically, Fast Page Mode DRAM is the slowest type of memory technology compatible with modern PCs and can only be used on buses up to a maximum of 66MHz.
- EDO DRAM – Extended Data-Out Dynamic Random Access Memory is only marginally (5%) faster than FPM DRAM based on the concept of allowing a memory access to begin before the last one is finished. This saves time by overlapping the processes required to retrieve a set of data. Like FPM DRAM, it can only be used on computer systems with memory bus speeds of up to the recommended 66MHz.
- SDRAM - Synchronous Dynamic Random Access Memory departed from FPM and EDO DRAM’s architecture and can be run on systems with higher memory bus speeds (100Mhz and more). Despite the improvements over older memory technology, SDRAM is only marginally (5%) faster than EDO DRAM. However, the main objective of SDRAM was to be able to use RAM on higher memory bus speeds.
- DDR SDRAM – Double Data Rate Synchronous Dynamic Random Access Memory is quite a long name when you think about it :o) DDR SDRAM is based on the SDRAM concept with just one exception – doubling the number of read or write operations to two accesses per system clock cycle. This effectively double the memory bandwidth over conventional SDRAM.
- DRDRAM – Direct Rambus Dynamic Random Access Memory offers the largest departure to conventional RAM architecture. The concept centres on the high-speed, but narrow, Direct Rambus Channel.DRDRAM gained recognition when Intel decided to create chipsets to work specifically with the Rambus technology.
