Cyclone V GT DDR3 HMC memory size

Hi all,

I am using DDR3 hard memory controller (HMC) on a Cyclone V GT development kit. In the altera website(https://www.altera.com/products/boards_and_kits/dev-kits/altera/kit-cyclone-v-gt.html), it says it has got 384MB, however, the avalon interface for a 128bit data gives only 21 bit address bus. So, if we do the math (2^21) * 128/8 gives areound 33MB and not 384MB. How can I use the 384MB specified in the Altera Website?

Any help is much appreciated. Thanks.

Kind regards,

Lijo