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Difference Between DMA and PIO
DMA (Direct Memory Access) and PIO (Programmed Input/Output) are two techniques of data transport between a peripheral device and a computer system. DMA (Direct Memory Access) is a data transfer method in which a peripheral device can directly access system memory without involving the CPU. PIO is a technique that allows the CPU to handle data transfers between a peripheral device and system memory.
Read this article to find out more about DMA and PIO and how they are different from each other.
What is DMA?
DMA is a data transfer method in which a peripheral device can directly access system memory without involving the CPU. The DMA controller is a specialised hardware component that handles data transfers between peripheral devices and system memory.
DMA is often used in high-speed data transfer applications such as transferring big files between a hard disc and system memory or streaming music or video data. DMA can increase the speed of these applications dramatically by reducing the amount of CPU overhead necessary to control data transfer.
They are faster than PIO transfers because DMA transfers do not require the CPU to manage the data transfer. Depending on the capabilities of the DMA controller and the peripheral device, DMA transfers are able to achieve transfer rates close to the maximum transfer rate of the peripheral device and system memory.
DMA comes in numerous types, including single-cycle DMA, block DMA, and scatter-gather DMA. Single-cycle DMA is the most basic type of DMA, with only one data transfer between the peripheral device and system memory. Block DMA carries data between a peripheral device and system memory, whereas scatter- gather DMA transfers data between several non-contiguous memory regions.
What is PIO?
PIO is a technique that allows the CPU to handle data transfers between a peripheral device and system memory. PIO transfers, which are frequently used in low-speed data transfer applications, are slower and less efficient than DMA transfers.
PIO refers to a method to transfer data between a peripheral device and a computer system. The CPU manages the data transfer between the peripheral device and system memory during a PIO transfer.
During a PIO transfer, the CPU sends a request to the peripheral device to transmit data to or from the system memory. The peripheral device then transfers data to or from system memory one byte at a time, and the CPU manages the transfer by reading or writing each byte of data.
PIO transfers are slower than DMA transfers because the CPU manages the data transfer, which can create a bottleneck if the CPU is busy with other tasks. PIO transfers also require more CPU overhead than DMA transfers, which can slow down overall system performance.
Difference between DMA and PIO
The following table highlights the major differences between DMA and PIO −
Characteristics |
DMA |
PIO |
|---|---|---|
Definition |
DMA (Direct Memory Access) is a data transfer method in which a peripheral device can directly access system memory without involving the CPU. |
PIO is a technique that allows the CPU to handle data transfers between a peripheral device and system memory. |
Data transfer speed |
The data transfer speed of DMA is faster compared to PIO because it doesn't involve the CPU. |
The data transfer speed of PIO is slower compared to DMA because it involves the CPU. |
Involvement of CPU |
It doesn't involve the CPU. |
It involves the CPU. |
Complexity |
DMA is more complex compared to PIO because it requires specialised hardware |
PIO is less complex compared to DMA because it depends on software to control the data transfer process. |
CPU Utilization |
The usage of CPU is less in DMA. |
The usage of CPU is more in PIO. |
Suitability |
It is suitable for transferring large amounts of data between peripheral devices and main memory. |
It is suitable for transferring a small amount of data between peripheral devices and main memory. |
Conclusion
In conclusion, DMA and PIO are two different data transmission mechanisms between a peripheral device and a computer system. DMA allows direct data transmission between a peripheral device and system memory without requiring the CPU to intervene, whereas PIO requires the CPU to manage the data transfer.
DMA is more efficient and faster than PIO, but it requires additional hardware and software support. The decision between DMA and PIO depends on the application's specific requirements, such as data transfer speed and volume, as well as the availability of hardware and software support.
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