Page 50 - Computer_Science_F5

Magnetic disk make them suitable For cache memory, four primary
for their respective levels in the questions must be answered
memory hierarchy. Use examples regarding block placement, block Chapter One: Computer architecture
to illustrate how each technology’s identification, block replacement,
speed, cost, and storage capacity and write strategy:
FOR ONLINE READING ONLY
contribute to the overall efficiency (i) Cache identification: How do
of the system you identify if the information
4. Flash memory, characterised by requested by the CPU is
non-volatility, portability and available in the cache?
reasonable speed has revolutionised (ii) Cache placement: When a
the way we store and access data block is transferred from a
in the 21st century. Research on lower memory level, where
applications of Flash memory. do you place the block in the
cache?
(iii) Cache replacement: When the
Cache memory cache is full, which block will
Cache memory is a smaller, faster memory be replaced to make room for
that stores copies of data from the most an incoming block?
frequently used main memory locations.
Within a computer, cache memory can be Similar to the cache memory concepts
designed as either split or unified. above, imagine you are a student with a
(a) Split cache: This design features small locker (your cache) close to your
separate caches for data and classroom. This locker holds the books
instructions. Both caches can you use most often for quick access
work simultaneously, improving during classes, but has limited capacity,
bandwidth by fetching data and just like a cache.
instructions at the same time. (a) Finding a spot (Cache placement):
However, it can be less efficient as When you get a new book from the
it rigidly divides the available space. library, you must decide where to
put it in your locker. Do you put

(b) Unified cache: In this approach, data it in the first empty slot, or do you
and instructions reside in the same consider which books you will need
cache. This offers more flexibility as next and put it closer to the front?
the entire cache space can be used for Cache placement strategies work
either data or instructions, potentially similarly, deciding where to put new
leading to a higher hit rate. However, information in the cache is based on
unified caches can limit bandwidth future needs.
as data and instructions compete for (b) Checking your locker (Cache
access. identification): While studying, if

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Student’s Book Form Five

Computer Science Form 5.indd 41 23/07/2024 12:32