Transfer (computing) on PCIE

In computer technology, transfers per second and its more common derivatives gigatransfers per second (abbreviated GT/s) and megatransfers per second (MT/s) are informal language that refer to the number of operations transferring data that occur in each second in some given data-transfer channel. 


T/s (number of transfers per second) = (clock speed) * (transfers per clock cycle)
For example: 4 GT/s = 1 GHz * 4 transfers per cycle


Intel® Core™ Processor Specification:
PCI Express*:
 - Gen1 Raw bit-rate on the data pins of 2.5 GT/s, resulting in a real bandwidth per pair of 250 MB/s given the 8b/10b encoding used to transmit data across this interface. This also does not account for packet overhead and link maintenance. 
 - Maximum theoretical bandwidth on the interface of 4 GB/s in each direction simultaneously, for an aggregate of 8 GB/s when x16 Gen 1


"aggregate", meaning they double the number to reflect simultaneous reading and writing.


Example:
---------------------------------------------------------------
PCIe v1.0(Gen 1) x 1: 
Bus Size: 1 bit = 1/8 Byte
Baud: 2.5 GT/s = 2500 MT/s
Encoding: 8b/10b
Bit Rate: 250 MB/s = (1/8) * 2500 * (8/10)


Maximum theoretical bandwidth(x16): 8GB/s = 2 * (250 MB/s* 16)