I'm a little confused. Hopefully HN can teach me. At 1 GB isn't the 64-bit detrimental? I thought 64-bit addressing cost about 5-10% of performance, but didn't matter since the system has hundreds of more MB of RAM.
I guess this makes sure it runs on more modern operating systems. I thought that most still support 32-bit.
64 bits means bigger integers before overflow, wraparound or whatever. Big ints may be useful when working with big data. It also means double precision floating point will tend to be faster. That may be useful in signal processing applications.
All that said, mainly the board is 64b because popular recent versions of the ARM core are 64b. The Raspberry Pi 3 is also 64b but Raspbian Linux typically comes as 32b...or at least did last I looked.
32-bit refers to the memory addressing. There's nothing that says that a 32-bit processor has to have 32-bit instructions, 32-bit ALU, etc. And most 32-bit processors are perfectly capable of working with long-int/double types.
Assuming the processor is otherwise identical, 64-bit addressing on a SoC with 1 GB of RAM doesn't do anything except waste memory on an excessive address space.
I think that historically, n-bits refers to the architecture's word length and that may or may not match the size of the address bus for a particular processor. Likewise, historically, multiple smaller than word-length data structures were sometimes packed into single words. The mantissa and exponent of IEEE 754 kinda' sorta' do something like that if I squint real hard.
Not that bitpacking words is particularly execution efficient, but maybe the space savings is worth it. Probably the sort of thing that's worth benchmarking in an actual app. Likewise with memory usage; I mean 1GB may be more than enough for a particular application and minimizing the OS may be a useful tradeoff for saving halving reads on 64b or greater data structures.
Anyway, the intent of my comment was to provide an explanation not promote one dogma over another...I think the big reason the SoC is 64b is 64b seems to be a sweet spot in the ARM powered credit card sized computer market place right now. And if I were considering this board but 2GB RAM was a concern, I'd probably go with an AllWinner board with that much. For example a BananaPi: http://www.banana-pi.org/
Supposedly ARM64 is more efficient than ARM32 clock per clock (better IPC). I know Apple made a big deal about it when they switched. I think it's partially due to them ditching some backwards compatibility braindamage.
I guess this makes sure it runs on more modern operating systems. I thought that most still support 32-bit.