11-10-2010, 04:35 PM
This article is presented by:
AJIN R
CONTENT ADDRESSABLE MEMORY
OBJECTIVES
To familiarise with structure,features and working of CAM
Types of CAM and CAM cells.
Applications of CAM.
Working of CAM as search engines in Networking.
Future scopes of CAM.
INTRODUCTION
Memory devices store and retrieve data by addressing specific memory location.
The time required to find an item stored in memory an be reduced if the item is identified by its content rather than by its address.
Content-addressable memories (CAMs) are hardware search engines that are much faster than algorithmic approaches for search-intensive applications.
What is CAM?
Content Addressable Memory is a special kind of memory!
Read operation in traditional memory:
Input is address location of the content that we are interested in it.
Output is the content of that address.
In CAM it is the reverse:
Input is associated with something stored in the memory.
Output is location where the associated content is stored
CAM Features
CAM Cascading:
We can cascade up to 8 pieces without incurring performance penalty in search time (72 bits x 512K).
We can cascade up to 32 pieces with performance degradation (72 bits x 2M).
Terminology:
Initializing the CAM: writing the table into the memory.
Learning: updating specific table entries.
Writing search key to the CAM: search operation
Handling wider keys:
Most CAM support 72 bit keys.
They can support wider keys in native hardware.
Shorter keys: can be handled at the system level more efficiently.