Register vs Memory FPGA Cyclone V

A register is single bit storage. It's part of the ALMs (adaptive logic modules) that make up the fabric of the FPGA. Carry chains between adjacent ALMs allow for the easy construction of shift registers. Registers use standard register control signals: synchronous or asynchronous reset, clock enable, etc.

Memory blocks are 2 dimensional storage arrays. They are addressable. They can be set up as single or dual port RAMs.

You can certainly set up registers as a memory array. However, using the dedicated memory blocks is more resource efficient and provides more memory specific options that can give you better performance.

I'd recommend reading the appropriate sections of the device handbook for the device you are targeting that discusses these resources to get more details.

https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/cyclone-v/cv_5v2.pdf

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A register is single bit storage. It's part of the ALMs (adaptive logic modules) that make up the fabric of the FPGA. Carry chains between adjacent ALMs allow for the easy construction of shift registers. Registers use standard register control signals: synchronous or asynchronous reset, clock enable, etc.

Memory blocks are 2 dimensional storage arrays. They are addressable. They can be set up as single or dual port RAMs.

You can certainly set up registers as a memory array. However, using the dedicated memory blocks is more resource efficient and provides more memory specific options that can give you better performance.

I'd recommend reading the appropriate sections of the device handbook for the device you are targeting that discusses these resources to get more details.

https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/cyclone-v/cv_5v2.pdf

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How about's built memory? Is 2-Port RAM is built memory of Cyclone V? Between SDRAM and 2-Port RAM, which is better?

The memory blocks are dedicated resources in the FPGA fabric. External SDRAM has much higher memory capacity, but requires you to set up a controller and interface. Again, check the device handbook and the external memory interface handbook for details:

https://www.altera.com/support/literature/lit-external-memory-interface.html