Computer Components Group 1

Computer Components Overview

• Members of Group 1 involved in discussing computer components include Alfred Giranyutha, Alex Matindi Githinji, Gideon Mutuku, Daniella Chege, Naggayi Shifrah Kasujja, Nathaniel William Mwabili, and Christopher Mbugua.

Memory Types

• Memory in a computer is essential for storing data and instructions, often categorized into Cache, Internal, and External memory.

Cache Memory

• Cache memory is a small, high-speed storage area that stores copies of frequently accessed data from main memory.
• Cache memory improves speed by delivering data quickly; it operates on the principle of "cache hits" (data found) and "cache misses" (data not found).
• Three levels of cache:
  • Level 1 (L1): Fastest and smallest, embedded in the CPU.
  • Level 2 (L2): Larger but slightly slower than L1, can be on the CPU or separate chip.
  • Level 3 (L3): Slowest of the three, but has the most capacity.

Cache Mapping

• Cache mapping determines how data from main memory is transferred to the cache.
• Direct Mapping: Each memory block maps to a specific cache line.
• Associative Mapping: Any cache location can hold any memory address; it is more flexible and faster for data retrieval.
• Set Associative Mapping: Combines direct and associative mapping, allowing a group of memory addresses to map to a set.

Internal Memory

• Also known as primary memory, it includes RAM, ROM, and cache memory.
• Internal memory is directly accessible by the CPU and is typically volatile.
• Read-Only Memory (ROM): Non-volatile, stores essential instructions and starts up the computer.
  • Types include PROM, EPROM, EEPROM, and MROM.
• Random Access Memory (RAM): Volatile, temporarily holds data the CPU is working on; types include DRAM, SRAM, SDRAM, and DDR SDRAM.

Functions of Internal Memory

• Stores and retrieves instructions quickly for running applications.
• Enables multitasking by providing immediate access to more data.
• Optimizes CPU performance and responsiveness.
• Stores temporary data lost upon power off and aids in system booting.

External Memory

• Known as secondary or auxiliary memory, it is non-volatile, with larger storage capacities compared to internal memory.
• Used for data backup, archiving, and long-term storage.
• Types include magnetic storage (HDDs, tape drives), optical storage (CDs, DVDs), and solid-state storage (SSDs, USB flash drives).

Comparison: Internal vs External Memory

• Access Speed: Internal memory is faster; external memory is slower.
• Volatility: Internal is volatile; external is non-volatile.
• Storage Type: Internal comprises semiconductor memory; external includes magnetic, optical, and solid-state.
• Storage Capacity: Internal has smaller capacities; external has larger capacities.
• Cost: Internal is more expensive per GB; external is less expensive.
• Examples: Internal includes RAM and ROM; external includes HDDs, SSDs, and USB drives.
• Primary Function: Internal is for immediate CPU data; external is for long-term data retention.

Input/Output Modules

• I/O modules interface between a computer and peripherals for data transmission.
• Types of I/O modules include digital, analog, and specialty modules.
• Digital I/O Modules: Handle binary signals from sensors and control devices.
• Analog I/O Modules: Convert analog signals to digital and vice versa.

Functions of I/O Modules

• Enable signal conversion (analog to digital and digital to analog).
• Provide isolation to protect the system from electrical noise.
• Perform signal conditioning for accurate signals suitable for processing.
• Support multiplexing for handling multiple signals effectively.
• Detect and report errors in signal transmission.

Input/Output Processes

• Input/output operations can use methods like Direct Memory Access (DMA), Programmed I/O, and Interrupt I/O.
• Programmed I/O: CPU controls I/O data transfer through program instructions.
• The CPU waits for the I/O operation to finish, potentially wasting time.

Direct Memory Access (DMA)

• DMA allows large data quantities to be transferred without CPU intervention, utilizing the system bus efficiently.### Direct Memory Access (DMA)
• DMA allows a processor to read/write data without continuous CPU involvement.
• Instructions from the processor to the DMA include:
  • The type of operation (read/write) via a control line.
  • The I/O device address communicated through data lines.
  • The memory starting location specified and stored in the DMA's address register.
  • The number of data words to be transferred stored in the DMA's data count register.
• Data is transferred one word at a time directly between memory and I/O devices, bypassing the CPU.
• Upon completion of the data transfer, the DMA sends interrupt signals to the CPU, involving it only at the beginning and end of data operations.

Interrupt-Driven I/O

• Traditional programmed I/O can degrade system performance due to the CPU waiting for I/O operations, leading to inefficient use of processing time.
• The Interrupt-driven I/O technique optimizes performance by allowing the processor to execute commands while awaiting I/O readiness.
• When the I/O module is ready, it interrupts the CPU, which pauses its current task to manage the data transfer.
• After the transfer, the CPU resumes its previous work.
• Comparatively, interrupt-driven I/O is more efficient than programmed I/O as it reduces idle CPU time but still requires the processor to handle every word transferred between memory and I/O modules.