what is the difference passmark loopback

[testlog]

passmark do sell the parallel and serial loopback with butnintest software.
What is the difference between passmark and common loopback plug?
The normal RS232 loopback is just a DB9 connector,and jump wire inside to make Rx&Tx link to each other.

[David (PassMark)]

There is really no such thing as a standard "common loopback plug".

You can find the pinouts for our serial and parallel plugs here. The USB loopback is much more complex & has a micorprocessor in the device, EEPROM, Firmware and a device driver.