Oscillations: The Rhythmic Heartbeat of Physics Oscillations describe any system that moves back and forth in a periodic manner. The most familiar example might be the swinging of a pendulum, but oscillatory behavior occurs in countless natural systems, from the vibrations of molecules to the orbits of celestial bodies. Key Concepts in Oscillations: Simple Harmonic Motion (SHM) : This is the most basic type of oscillation, where the restoring force acting on an object is proportional to its displacement. Classic examples include a mass on a spring or a pendulum swinging with small amplitudes. The equations governing SHM are simple, but they form the basis for understanding more complex oscillatory systems. Damped and Driven Oscillations : In real-world systems, oscillations tend to lose energy over time due to friction or air resistance, leading to damped oscillations . In contrast, driven oscillations occur when an external force continuously adds energy to the system, preventing i
Direct Memory Access
* For devices that moves large quantities of data ( such as disk controllers ), it is wasteful to tie up the CPU transferring data in and out of registers one byte at a time.
* Instead this work can be off-loaded to a special processor, called as the Direct Memory Access, DMA, Controller.
* The host issues a command to the DMA controller, implicating the location where the data is located, the location where the data is to be moved to, and the number of bytes of data to moved. The DMA controller handles the data moved, and then interrupts the CPU when the transfer is complete.
* A simple DMA controller is a quality component in modern PCs, and many bus-
mastering I/O cards contain their possess DMA hardware.
* Handshaking between DMA controllers and their devices is fulfil by two wires called the DMA-request and DMA-acknowledge wires.
* While the DMA moves is going on the CPU does not have process to the PCI bus (including main memory ), but it does have process to its internal registers and primary and secondary caches.
* DMA can be complete in terms of either physical addresses or virtual addresses that are mapped to physical addresses. The latter method is known as Direct Virtual Memory Access, DVMA, and permits direct data transfer from one memory-mapped device to another without having the main memory chips.
* Direct DMA access by user processes can speed up operations, but is normally forbidden by modern systems for protection and security reasons. ( I.e. DMA is a kernel-mode operation. )
* Figure below shows the DMA process.
