04. Memory and Input Output Devices
Chapter 4: Primary Memory
1. Introduction to Computer Memory
Computer memory is an electronic storage area that allows quick access to instructions and data for the processor. It is generally divided into two categories:
Primary Memory: Handles the data actively in use.
Secondary Memory: Stores data that is not currently in use, often referred to as output storage.
2. Motherboard Components
The motherboard serves as the central printed circuit board in a computer, incorporating several critical components:
Northbridge: Connects the CPU to high-speed devices like RAM.
Southbridge: Manages slower peripheral devices.
DRAM & ROM: Types of memory used in a computer.
PCI slots: Connect peripheral cards for additional functionality.
Power Connectors and Mounting Points: For powering and cooling the system, respectively.
3. Memory Representation
Memory is fundamentally represented using bits and bytes:
1 Bit: A binary digit representing two states (0 or 1).
1 Byte: Consists of 8 bits.
Memory sizes are classified as:
1 KiloByte (KB) = 1024 Bytes
1 MegaByte (MB) = 1024 KB
1 GigaByte (GB) = 1024 MB
1 TeraByte (TB) = 1024 GB
4. Memory Hierarchy
Access time and capacity define the memory hierarchy:
Internal Processor Memory: Includes cache memory and special registers in the CPU for efficient access.
Primary Memory: RAM and ROM, integral for active processing.
Secondary Memory: Non-volatile storage, includes hard disks and tapes, which are accessed through I/O routines.
5. Storage Evaluation Criteria
Important factors for evaluating storage include:
Storage Capacity: The amount of data it can hold.
Cost: Evaluated per bit of storage.
Access Time: The duration between the request and the completion of read/write operations.
Physical Characteristics: Consist of electronic, magnetic, mechanical, and optical components.
Permanence of Storage: Determines if data is retained after power loss.
Access Modes: Such as sequential and random access.
6. Read-Only Memory (ROM)
ROM is a type of non-volatile memory that can only be read, not written to. Key points include:
Stores critical instructions needed for startup (bootstrap process).
Includes BIOS, which is essential for the booting process.
Different types of ROM:
Masked ROM: Hard-wired with pre-programmed data.
Programmable ROM (PROM): User-programmable once.
Erasable Programmable ROM (EPROM): Can be erased using ultraviolet light and reprogrammed.
Electrically Erasable Programmable Read-Only Memory (EEPROM): Can be selectively erased and reprogrammed.
Flash ROM: A type of EEPROM that is faster and can be erased in blocks.
7. Advantages of ROM
Non-volatile and cannot be accidentally changed.
More reliable than RAM and cheaper per byte.
Static nature means it does not require refreshing, enabling easy verification of contents.
8. Random Access Memory (RAM)
RAM is the primary memory used for storing data actively in use. Characteristics include:
Volatile nature means data is lost when power is switched off.
Data access is random and relatively expensive.
9. Types of RAM
Key variations of RAM include:
Static RAM (SRAM): Retains data as long as power is supplied; used as cache due to speed.
Dynamic RAM (DRAM): Needs periodic refreshing; cheaper and smaller than SRAM.
10. Main vs Secondary Memory
Main Memory:
Also known as primary memory.
Volatile; data lost when power is cut off.
Essential for processing and temporary data storage.
Secondary Memory:
Non-volatile and slower than RAM.
Used for permanent data storage.
Examples include hard disks, CDs, and USB drives.
11. Difference Between RAM and ROM
RAM: Fast, volatile, and allows for both read/write operations; more expensive.
ROM: Non-volatile, read-only, and designed for permanent storage of firmware.
12. Storage Devices
Secondary storage devices enable long-term data retention and include:
Hard disks (Internal/External), CDs, DVDs, and USB drives.
13. Hard Disk Mechanics
Composed of platters and tracks; smallest unit is a sector (typically 512 bytes).
Non-volatile storage that holds operating systems and software.
14. Conclusion
Understanding primary memory is crucial for appreciating how computers process information and perform tasks effectively. The categorization into RAM and ROM allows for organized storage, with their distinct roles in computing architecture.
04. Memory and Input Output Devices
Chapter 4: Primary Memory
1. Introduction to Computer Memory
Computer memory is an electronic storage area that allows quick access to instructions and data for the processor. It is generally divided into two categories:
Primary Memory: Handles the data actively in use.
Secondary Memory: Stores data that is not currently in use, often referred to as output storage.
2. Motherboard Components
The motherboard serves as the central printed circuit board in a computer, incorporating several critical components:
Northbridge: Connects the CPU to high-speed devices like RAM.
Southbridge: Manages slower peripheral devices.
DRAM & ROM: Types of memory used in a computer.
PCI slots: Connect peripheral cards for additional functionality.
Power Connectors and Mounting Points: For powering and cooling the system, respectively.
3. Memory Representation
Memory is fundamentally represented using bits and bytes:
1 Bit: A binary digit representing two states (0 or 1).
1 Byte: Consists of 8 bits.
Memory sizes are classified as:
1 KiloByte (KB) = 1024 Bytes
1 MegaByte (MB) = 1024 KB
1 GigaByte (GB) = 1024 MB
1 TeraByte (TB) = 1024 GB
4. Memory Hierarchy
Access time and capacity define the memory hierarchy:
Internal Processor Memory: Includes cache memory and special registers in the CPU for efficient access.
Primary Memory: RAM and ROM, integral for active processing.
Secondary Memory: Non-volatile storage, includes hard disks and tapes, which are accessed through I/O routines.
5. Storage Evaluation Criteria
Important factors for evaluating storage include:
Storage Capacity: The amount of data it can hold.
Cost: Evaluated per bit of storage.
Access Time: The duration between the request and the completion of read/write operations.
Physical Characteristics: Consist of electronic, magnetic, mechanical, and optical components.
Permanence of Storage: Determines if data is retained after power loss.
Access Modes: Such as sequential and random access.
6. Read-Only Memory (ROM)
ROM is a type of non-volatile memory that can only be read, not written to. Key points include:
Stores critical instructions needed for startup (bootstrap process).
Includes BIOS, which is essential for the booting process.
Different types of ROM:
Masked ROM: Hard-wired with pre-programmed data.
Programmable ROM (PROM): User-programmable once.
Erasable Programmable ROM (EPROM): Can be erased using ultraviolet light and reprogrammed.
Electrically Erasable Programmable Read-Only Memory (EEPROM): Can be selectively erased and reprogrammed.
Flash ROM: A type of EEPROM that is faster and can be erased in blocks.
7. Advantages of ROM
Non-volatile and cannot be accidentally changed.
More reliable than RAM and cheaper per byte.
Static nature means it does not require refreshing, enabling easy verification of contents.
8. Random Access Memory (RAM)
RAM is the primary memory used for storing data actively in use. Characteristics include:
Volatile nature means data is lost when power is switched off.
Data access is random and relatively expensive.
9. Types of RAM
Key variations of RAM include:
Static RAM (SRAM): Retains data as long as power is supplied; used as cache due to speed.
Dynamic RAM (DRAM): Needs periodic refreshing; cheaper and smaller than SRAM.
10. Main vs Secondary Memory
Main Memory:
Also known as primary memory.
Volatile; data lost when power is cut off.
Essential for processing and temporary data storage.
Secondary Memory:
Non-volatile and slower than RAM.
Used for permanent data storage.
Examples include hard disks, CDs, and USB drives.
11. Difference Between RAM and ROM
RAM: Fast, volatile, and allows for both read/write operations; more expensive.
ROM: Non-volatile, read-only, and designed for permanent storage of firmware.
12. Storage Devices
Secondary storage devices enable long-term data retention and include:
Hard disks (Internal/External), CDs, DVDs, and USB drives.
13. Hard Disk Mechanics
Composed of platters and tracks; smallest unit is a sector (typically 512 bytes).
Non-volatile storage that holds operating systems and software.
14. Conclusion
Understanding primary memory is crucial for appreciating how computers process information and perform tasks effectively. The categorization into RAM and ROM allows for organized storage, with their distinct roles in computing architecture.
