Page 49 - Computer_Science_F5

Computer Science to the cache. Higher levels in the cost-effectiveness and capacity but is
hierarchy have larger miss penalties.
slower compared to other memory types.
SRAM (Static Random Access Memory):
Write operations: when data needs to Used in registers and cache, it has faster
be written, the write operation might access times due to its transistor-based
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update all copies across different levels circuits that hold data without constant
(cache and main memory) to maintain refreshing. However, its complex circuitry
consistency (depending on the written makes it more expensive and limits its
policy). capacity.

Cache coherence protocols: mechanisms Flash memory: Is a non-volatile alternative
are employed to ensure all copies of data to traditional hard drives, using floating-
across different levels are consistent, gate transistors to store data even when the
especially when multiple processors are power is off. It is ideal for storing personal
involved. files, applications, and operating systems
but is slower than DRAM and SRAM.
Average Memory Access Time
(AMAT) Magnetic disk: This technology is used
Average memory access time is the average in hard disk drives (HDDs), offers the
time to access memory considering both most cost-effective way to store large
hits and misses and the frequency of amounts of data permanently. Despite
different accesses. AMAT captures the its vast storage capacities, it has slower
fact that the time to access data for both access times due to the mechanical
hits and misses affects performance. This nature of data storage.
information helps computer architects to
examine alternative cache designs. Exercise 1.8
AMAT = Hit times + Miss rate × Miss penalty 1. Find the Average Memory Access

Time (AMAT) for a processor with
Computer memory technologies a cache hit rate of 95%, a hit time
The memory hierarchy within a computer of 4ns, and a miss penalty of 80 ns
system balances speed, size, and cost 2. Given a computer system with
using four primary memory technologies: varying memory requirements,
DRAM, SRAM, Flash, and Magnetic explain how each level of the
Disk.
memory hierarchy (cache, main

DRAM (Dynamic Random Access memory, and secondary storage)
Memory): Forms the main memory optimises system performance and
foundation, storing data as electrical cost-effectiveness.
charges in capacitors that need constant 3. Discuss how the characteristics of
refreshing. It offers a balance between DRAM, SRAM, Flash Memory, and

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Computer Science Form 5.indd 40 23/07/2024 12:32