COMPUTER ARCHICTURE AND ORGINATION
UNIT 2 MEMORY UNIT
COVERED TOPICES:- Basic Concepts, Memory Hierarchy, Semiconductor RAM Memories, Internal Organization of Memory Chips, Static Memories, Dynamic Memories, Read Only Memories, Speed, Size and Cost.Q1. Connection of Memory to Processor
The memory is connected to the processor through a memory bus. This connection allows the processor to read and write data to and from the memory. The memory controller plays a crucial role in managing this communication.
The Memory Controller:
- The memory controller acts as an interface between the processor and the memory modules.
- It manages the flow of data between the processor and memory.
- It interprets memory requests from the processor and translates them into the appropriate signals for the memory modules.
- Additionally, it handles tasks such as refreshing dynamic memory and coordinating access to shared memory resources.
Q2. Synchronous DRAM (SDRAM)
Synchronous DRAM is a type of dynamic random-access memory (DRAM) that synchronizes its operation with the system clock.
Explanation:
- SDRAM operates in synchronization with the system clock, allowing for faster data transfer rates compared to asynchronous DRAM.
- It has separate input and output paths, enabling concurrent read and write operations.
- SDRAM modules are commonly used in computer systems for main memory due to their higher performance.
Q3. SRAM vs. DRAM Comparison
| Aspect | SRAM | DRAM |
|---|---|---|
| Speed | Faster | Slower |
| Size | Larger | Smaller |
| Cost | Higher | Lower |
Q4. Internal Organization of Dynamic Memory Chip
The internal organization of a dynamic memory chip typically includes a memory array, row and column decoders, sense amplifiers, and I/O circuits.
Explanation:
- The memory array stores data in cells, which are organized into rows and columns.
- Row and column decoders select the appropriate row and column lines for read or write operations.
- Sense amplifiers amplify the weak signals from the memory cells during read operations.
- I/O circuits manage data transfer between the memory chip and external devices.
Q5. Realization of 2M*32 Memory Modules Using 512K*8 Static Memory Chips
Four 512Kx8 static memory chips are utilized to construct a 2Mx32 memory module. Each memory chip encompasses 512K addressable locations denoted by A0-A18 and 8 data lines labeled as D0-D7. Considering the requirement for a 32-bit word, which includes 32 data lines, the addressing necessitates 21 address lines (A0-A20) to uniquely identify each memory location within the 2M addressable space.
Memory Unit in Computer Architecture & Organization
1. Basic Concepts
In computer architecture and organization, memory is the essential component that stores data and instructions for processing by the CPU. It provides fast access to information, enabling the computer to perform tasks efficiently. Memory units come in various types, each with its own characteristics and capabilities.
2. Memory Hierarchy
The memory hierarchy is a concept that organizes different types of memory based on their proximity to the CPU and their access speed. It typically consists of several levels:
- Registers: Registers are the fastest and smallest type of memory located within the CPU. They store data temporarily during processing.
- Cache Memory: Cache memory is a small but fast type of memory located between the CPU and main memory. It stores frequently accessed data and instructions to speed up processing.
- Main Memory (RAM): RAM is the primary memory used for storing data and program instructions that are actively being processed by the CPU. It offers fast access times but is volatile, meaning its contents are lost when the power is turned off.
- Secondary Storage: Secondary storage devices, such as hard disk drives (HDDs) and solid-state drives (SSDs), provide long-term storage for data and programs. They offer larger storage capacities but slower access times compared to main memory.
3. Semiconductor RAM Memories
Semiconductor RAM (Random Access Memory) is the predominant type of memory used in modern computer systems. It allows data to be read from and written to randomly, making it suitable for dynamic data storage. Semiconductor RAM memories include:
- Dynamic RAM (DRAM): DRAM stores data using capacitors, which must be periodically refreshed to maintain their contents. It offers high storage density and is commonly used as main memory in computer systems.
- Static RAM (SRAM): SRAM uses flip-flops to store data, making it faster and more power-efficient than DRAM. It is commonly used in cache memory and registers.
4. Internal Organization of Memory Chips
Memory chips are organized into a grid-like structure of rows and columns, with each intersection forming a memory cell that can store a single bit of data. The internal organization of memory chips includes features such as:
- Address Lines: Address lines select specific memory locations for reading from or writing to.
- Data Lines: Data lines carry the actual data being read from or written to memory.
- Control Circuitry: Control circuitry manages the operation of memory chips, including reading, writing, and refreshing data.
5. Static Memories
Static memories, such as SRAM, store data using flip-flops, which retain their state as long as power is supplied. They offer fast access times and low power consumption but are more expensive and have lower storage density compared to dynamic memories.
6. Dynamic Memories
Dynamic memories, such as DRAM, store data using capacitors, which require periodic refreshing to maintain their contents. They offer higher storage density and are more cost-effective than static memories but are slower and consume more power.
7. Read Only Memories
Read Only Memory (ROM) is a type of memory that retains its contents even when the power is turned off. ROM is used to store firmware, boot code, and other essential system software that should not be modified. Types of ROM include:
- ROM (Read Only Memory): ROM contains pre-programmed data that cannot be modified.
- PROM (Programmable Read Only Memory): PROM can be programmed once by the user using a special device called a PROM programmer.
- EPROM (Erasable Programmable Read Only Memory): EPROM can be erased and reprogrammed multiple times using ultraviolet light.
- EEPROM (Electrically Erasable Programmable Read Only Memory): EEPROM can be erased and reprogrammed electronically, making it more convenient than EPROM.
8. Speed, Size, and Cost
Memory technologies vary in terms of speed, size, and cost, making them suitable for different applications:
- Speed: Faster memory technologies, such as SRAM, are used in cache memory and registers to provide the CPU with quick access to frequently used data and instructions.
- Size: Memory size refers to the amount of data that can be stored in the memory unit. Main memory (RAM) typically offers larger storage capacities than cache memory but is slower in comparison.
- Cost: Memory cost is influenced by factors such as technology, manufacturing process, and demand. DRAM is more cost-effective than SRAM but offers lower performance.
