IDE data transmission mode (PIO, DMA)

With the development of technology, the product needs to improve the data transmission speed. The data transmission mode of the IDE interface hard disk has undergone three different technological changes, from the initial Pio mode, to the DMA mode, and then to the ultra DMA mode.

Pio Mode
The English spelling of PIO is "programming input/output model". Pio mode is a data exchange mode that reads and writes data by executing the I/O port command on the CPU. It is the earliest hard disk data transmission mode. The data transmission rate is low, and the CPU usage is also high. When a large amount of data is transmitted, the system will pause due to excessive CPU resources, you cannot perform other operations. Pio data transmission modes include Pio Mode 0, Pio Mode 1, Pio Mode 2, Pio Mode 3, and PIO Mode 4, the data transmission rate ranges from 3.3 MB/s to 16.6 Mb/s. Due to the low transmission rate and high CPU usage, this data transmission mode will soon be eliminated.

DMA mode
The English spelling of DMA is "Direct Memory Access", which means direct memory access. It is a data exchange mode that directly accesses data from the memory without going through the CPU. In PIO mode, data transmission between the hard disk and memory is controlled by the CPU. In DMA mode, the CPU only needs to issue commands to the DMA controller, let the DMA controller process the data transfer, and then feed back the information to the CPU after the data is transferred, which reduces the CPU resource share in a large process. The difference between the DMA mode and the PIO mode is that the DMA mode is not dependent on the CPU, which can greatly save system resources. The difference in transmission speed between the two is not very obvious. The DMA mode can be divided into single-word DMA (single-byte DMA) and Multi-word DMA (Multi-byte DMA). The maximum transmission rate can be only 16.6 Mb/s.

Ultra DMA mode
The English spelling of Ultra DMA is "Ultra Direct Memory Access", which is generally abbreviated as udma, meaning advanced Direct Memory Access. The udma mode uses the 16-bit multi-word DMA (16-bit multi-byte DMA) mode as the benchmark and can be understood as an enhanced version of the DMA mode, based on the advantages of the DMA mode, the CRC (cyclic redundancy check cyclic Verification Code) technology is added to improve the accuracy and security of the data transmission process. In the previous hard disk data transmission mode, data is transmitted only once in a clock period. In the udma mode, the double data rate (double data transmission) technology is gradually applied, therefore, the data transmission speed has been greatly improved. This technology implements a data transmission between the rising and descending phases of the clock, which can increase the data transmission speed exponentially.

After the development of the udma model to the udma133 mode, due to the technical specifications of IDE interfaces, both connectors, connection cables, and signal protocols have shown great technical bottlenecks, however, the maximum data transmission rate is also limited. At the same time, the transmission rate of the IDE interface is improved, that is, the working frequency is improved. defects such as aishenghuo interference, increasing ground wires, and Chaotic Signals also impose great limitations on its development. It is inevitable that it will be replaced by a new generation of SATA interfaces.