The data signaling rate is given by where m is the number of parallel channels, ni is the number of significant conditions of the modulation in the I-th channel, and Ti is the unit interval, expressed in seconds, for the I-th channel.
For serial transmission in a single channel, the DSR reduces to (1/T)log2n; with a two-condition modulation, i. e. n =2, the DSR is 1/T.
For parallel transmission with equal unit intervals and equal numbers of significant conditions on each channel, the DSR is (m /T)log2n; in the case of a two-condition modulation, this reduces to m /T.
The DSR may be expressed in bauds, in which case, the factor log2ni in the above summation formula should be deleted when calculating bauds.
In synchronousbinarysignaling, the DSR in bits per second may be numerically the same as the modulation rate expressed in bauds. Signal processors, such as four-phase modems, cannot change the DSR, but the modulation rate depends on the line modulation scheme, in accordance with Note 4. For example, in a 2400 bit/s 4-phase sending modem, the signaling rate is 2400 bit/s on the serialinput side, but the modulation rate is only 1200 bauds on the 4-phase output side.
Since the obvious objective in using a hard disk is to transfer data to the hard drive and onto the disks, or off the disks and out of the drive, the rate of data transfer is of paramount importance.
What we are talking about here is the rate at which the hard disk can physically read data from the surface of the platter and transfer it to the internal drive cache or read buffer, ready for sending over the interface to the system.
The internal data transfer rate, which is the real rate that data can be read from the disk, is often called the sustained transfer rate, while the external rate is called the peak or burst transfer rate.
The distance over which data moves within a computer may vary from a few thousandths of an inch, as is the case within a single IC chip, to as much as several feet along the backplane of the main circuit board.
The datarate of a channel is often specified by its bit rate (often thought erroneously to be the same as baud rate).
Data is typically grouped into packets that are either 8, 16, or 32 bits long, and passed between temporary holding units called registers.
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