# Mega transfer

The units megatransfer (MT, 10 6 transfers) or gigatransfer (GT, 10 9 transfers) per second are used in computer hardware to indicate the step speed of a connection. For example, 4 GT / s means that 4 × 10 9 (four billion) transfers per second (T / s) can be made. The resulting data transfer rate depends on the one hand on the amount of data per transfer and on the other hand on the number of lines ( lanes ) used in parallel . In addition, the overhead when using coding (e.g. error correction) must be taken into account.

An example: PCI-Express 2.0 allows 5 GT / s per lane and uses the 8b10b code for signal transmission, which encodes 8 bits of data in 10 bits. A transfer consists of a single bit per lane. A slot for graphics cards is usually connected with 16 lanes. The maximum possible data throughput is then:

${\ displaystyle {\ frac {5 \ {\ text {GT}}} {\ text {s}}} \ times {\ frac {1 \ {\ text {Bit}}} {{\ text {T}} \ cdot {\ text {Lane}}}} \ times {\ frac {\ text {8 Bit}} {\ text {10 Bit}}} \ times 16 \ {\ text {Lanes}} = {\ frac {64 \ {\ text {GBit}}} {\ text {s}}} = {\ frac {8 \ {\ text {GByte}}} {\ text {s}}}}$.

(Note: The last equation 8 Gbit = 1 GByte only works if the gigabyte is understood as a decimal gigabyte .)

A similar term, the symbol rate or baud rate, refers to the number of symbols transmitted per second. This can be understood to mean that it relates to the total number of symbols, i.e. increases accordingly when lanes are used in parallel. Transfer / second always refer to the pure walking speed, regardless of the number of lanes.