The motherboard doubles it, ddr = double data rate so I think name implies its doubled.
The next generation of SDRAM is DDR, which achieves greater bandwidth than the preceding single data rate SDRAM by transferring data on the rising and falling edges of the clock signal (double pumped). Effectively, it doubles the transfer rate without increasing the frequency of the clock.
Main difference between different types of DDR are the transfer speeds get faster. Seems I was wrong about being tripled, I didn't really know until I looked.
This might help: https://www.transcend-info.com/Support/FAQ-296