1. Cache Memory
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2. Objective:
On completion of this period, you would be able
to understand:
 Cache memory used in computers.
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3. Recap:
 What is meant by memory ?
A space to keep information.
It stores program, data results or any kind
of information.
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4. Cache Memory
 The word cache is pronounced as cash.
 Cache memory is placed between the CPU and
the main memory.
 It stores instructions and data which are to be
currently executed by the CPU.
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5. Cache Memory (contd...)
It is a semiconductor memory
It is not accessible to users i.e. information
cannot be written into cache memory by users.
It increases the speed of the computer up to
15%.
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6. Cache Memory (contd...)
 It consists of static RAMs.
 Its access time is 10ns which is much less than
that of the main memory i.e. 50ns
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7. Memory Hierarchy with cache memory
Cache Primary Secondary
CPU
Memory Memory Memory
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8. Types Of Cache Schemes
Write-through
Write-back
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9. Write-through
 Cache memory is updated each time when the
CPU writes into the cache.
 The advantage of the write through cache is that
the main memory always contains the same
data as the cache contains.
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10. Write-back
 Only the cache memory is updated during a
write operation.
 The updated locations in the cache are marked
by flags so that later on when the word is
removed from cache, it is copied into the main
memory.
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11. Write-back (contd)
 The words are removed from the cache time to
time to make room for a new block of words.
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12. Level of Cache Memory
1. First level cache (L1).
2. Second level cache (L2).
3. Third level cache (L3).
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13. Cache memory is placed at two or three
levels (contd)
 The resident cache is called Level – L1
(internal).
 In addition to the cache memory built into the
CPU, cache is also added to the motherboard.
 This motherboard- resident cache is often called
Level – L2 (external).
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14. Cache memory is placed at two or three
levels (contd)
 Some computers contain L1 and L2 within the
microprocessor.
 Cache memory within the processor is called
internal cache.
 The cache outside the processor is called
external cache.
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15. Summary:
In this class, we have learnt about
 About cache memory.
Levels of cache memory used in
computers.
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16. Frequently Asked Questions
1. What is a Cache Memory?
2. Explain levels of cache memory?
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17. Quiz:
1. Cache memory within the processor is called
internal cache?
a. Yes
b. No
Answer: a
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18. Quiz:
2. Cache consists of
a. static RAMs.
b. dynamic RAMs
Answer: a
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19. Quiz:
3. Cache is a
a. magnetic memory
b. semiconductor memory.
Answer: b
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