Lecture Notes 07: Memory

Outline

This class we'll discuss:

• Recap: The ALU
• Where is Memory?
• How fast is Memory?
• How big is Memory?
• How does Memory work?
• How long does Memory last?

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Recap: The ALU

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Memory Architecture (where is it?)

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Memory Architecture (relative speeds)

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Memory Architecture (relative sizes)

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Computer Design Trend (speed)

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Computer Design Trend (size)

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How does memory work?

from: The Architecture of Computer Hardware, Systems Software & Networking: An Information Technology Approach 4th Ed.



from: The Architecture of Computer Hardware, Systems Software & Networking: An Information Technology Approach 4th Ed.



from: The Architecture of Computer Hardware, Systems Software & Networking: An Information Technology Approach 4th Ed.

The 1-bit Memory cell

A flip-flop is a device which stores a single bit (binary digit) of data; one of its two states represents a "one" and the other represents a "zero". Such data storage can be used for storage of state, and such a circuit is described as sequential logic in electronics.

An example is shown below:



It works with two inputs: R and S.

1. While the R and S inputs are both low, feedback maintains the Q and Q outputs in a constant state, with Q the complement of Q.
2. If S (Set) is pulsed high while R (Reset) is held low, then the Q output is forced high, and stays high when S returns to low;
3. similarly, if R is pulsed high while S is held low, then the Q output is forced low, and stays low when R returns to low.

This allow the feedback to maintain a 0 or a 1.

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Memory Volatility

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Before next class (Tuesday 09/28)

[Due for everyone]

• Remember: Homework 2 (in Moodle), due on Wednesday 09/29 at 11:59 PM.

[Optional]

• Read the two memory readings in Moodle

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1-Minute Debrief

Please fill this out before leaving: