This smells like you have a problem. As Frank Thomas said, the transfert speed you have is way too low. Even a cheap motherboard perform better.
Have a look into your BIOS settings. You could find the reason. Or try to reset the BIOS to default values or optimal values. You can also reset the settings with the jumper on the motherboard.
Some BIOSes have hidden settings. Ask Google if you can find them for your.
You can also try to update the BIOS. But a so wide gap between your results and theory is probably not a BIOS version problem.