Memory organization Memory Organization in Computer Architecture. A memory unit is the collection of storage units or devices together. The memory unit stores the binary information in the form of bits. ... Volatile Memory: This loses its data, when power is switched off.

1. Memory Organization
Kazi Mahmudul Hassan sir
Department of Computer Science and Engineering
Jatiya Kab Kazi Nazrul Islam University, Trishal, Mymensingh, Bangladesh
Al-amin
Department of Electrical & Electronic Engineering
Jatiya Kab Kazi Nazrul Islam University, Trishal, Mymensingh, Banglade

2. Topics
• Review of primary and secondary memories;
• memory hierarchies;
• High-speed memories,
• Interleaved memories,
• Caches,
• associative memories.

3. What is Memory?
• Memory is very much like our brain as it is used to store data and
instructions.
• Computer memory is the storage space where data is to be processed,
and instructions needed for processing are stored.
• The memory is divided into a large number of smaller portions called
the cell. Every cell/ location has a unique address and a size.

4. Memories Classification
• Memory is a fundamental component of the computer that is
categorized into primary and secondary memory.
1.Primary
2.Secondary
• Primary memory is the main memory of the computer which can be
directly accessed by the central processing unit.
• Secondary memory refers to the external storage device which can
be used to store data or information permanently.

5. Primary And Secondary Memories Comparison
Parameter Primary memory Secondary memory
Nature The primary memory is categorized as volatile &
non-volatile memories.
The secondary memory is always a non-volatile memory.
Alias These memories are also called internal memory. Secondary memory is known as a Backup memory or
Additional memory or Auxiliary memory.
Access Data is directly accessed by the processing unit. Data cannot be accessed directly by the processor. It is
first copied from secondary memory to primary memory.
Only then CPU can access it.
Formation It's a volatile memory meaning data cannot be
retained in case of power failure.
It's a non-volatile memory so that that data can be
retained even after power failure.
Storage It holds data or information that is currently
being used by the processing unit. Capacity is
usually in 16 to 32 GB
It stores a substantial amount of data and information.
Capacity is generally from 200GB to terabytes.
Accesses Primary memory can be accessed by the data bus. Secondary memory is accessed by I/O channels.
Expense Primary memory is costlier than secondary
memory.
Secondary memory is cheaper than primary memory.

6. Primary And Secondary Memories

7. Memory Hierarchies
Or, Multilevel Memories Organization
Three key characteristics increase for a memory
hierarchy.
They are the access time, the storage capacity and the
cost

8. Memory
Hierarc
hies

9. Cache Memory
• In computing, a cache is a hardware or software component that stores data so that future requests
for that data can be served faster;
• The data stored in a cache might be the result of an earlier computation or a copy of data stored
elsewhere.
• A cache hit occurs when the requested data can be found in a cache, while a cache miss occurs when
it cannot.
• Cache hits are served by reading data from the cache, which is faster than recomputing a result or
reading from a slower data store; thus, the more requests that can be served from the cache, the
faster the system performs.

10. Cache Memory

12. Organization of Multilevel Memory System:
A memory system containing at least two memory subsystems with different capacity and
access-time attributes

13. Multilevel Caching
• Level 1: L1 (CPU)
• Level 2: L2 (Motherboard)
• Level 3: L3 (Main memory/RAM)

14. Difference Between SRAM and DRAM
Speed Faster Slower
Size Small Large
Cost Expensive Cheap
Used in Cache memory Main memory
Density Less dense Highly dense
Construction Complex and uses transistors and latches. Simple and uses capacitors and very
few transistors.
Single block of memory requires 6 transistors Only one transistor.
Power consumption Low High
BASIS FOR COMPARISON SRAM DRAM

15. Difference Between SRAM and DRAM

16. Below is the structure for SRAM and DRAM for 1 bit
storage.