CST8174_Lecture_21_RAM_Lecture

CST8174_Lecture_21_RAM_Lecture - Algonquin College CST8174...

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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 CST8174 Computer Technology Basics System Memory
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 System Memory We’ve looked at some of the mechanisms the CPU uses to process data But where does that data come from? Without system memory, all data – calculations, programs, etc. would be lost System would have no record of what it’s done, and no idea what to do next System memory acts as the workspace for the processor
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 Random Access Memory Remember that anything that holds data is memory The term random access means that any part of the memory can be accessed with equal ease Provides temporary storage for programs and data while the computer is running RAM is referred to as volatile in that when the computer is turned off the contents are lost
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 Random Access Memory The amount of RAM has a direct effect on the speed of a computer There are two main types in a computer system DRAM & SRAM
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 DRAM Dynamic RAM, stores data for a fraction of a second before it is lost Typically implements main system memory Installed as ‘sticks’ of memory, or small self-contained circuit boards Inexpensive relative to other forms of memory
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 DRAM Considered to be very dense, allowing a lot of data to be stored on a small chip A DRAM chip uses only one transistor and capacitor pair to store a single bit The electrical charges in the capacitors drain Therefore requires constant refreshing by the memory controller This results in a performance penalty and limits speed
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 SRAM Static RAM Maintains its contents as long as power is applied Very fast (~2 ns), but expensive and requires more power to operate Uses a cluster of six transistors to store a single bit Uses no capacitors, meaning no refreshing
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Tuesday, May 12, 2009 Matthew O’ Meara Algonquin College CST8174 SRAM SRAM is lower in density compared to other chips, making chips large and expensive Typically a SRAM chip is 30 larger and 30 times
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CST8174_Lecture_21_RAM_Lecture - Algonquin College CST8174...

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