Peripheral component interconnect express interface device and method of operating the same

A method of operating a Peripheral Component Interconnect Express (PCIe) interface device, the method comprising:

• counting a number of transaction layer packets transferred between multiple functions executed on one or more Direct Memory Access (DMA) devices and a host system per unit time;
• calculating throughputs of the multiple functions based on the number of transaction layer packets transferred per unit time;
• allocating traffic class values to transaction layer packets received from the multiple functions based on the throughputs of the multiple functions;
• outputting the transaction layer packets through virtual channels to which the transaction layer packets are mapped based on the traffic class values;
• and
• reallocating the traffic class values of the transaction layer packets when rankings of the throughputs of the multiple functions are changed.