What is the goal of declaring an array with an offset? [8:1] instead of [7:0]
I'm used to declare my signals with reg [7:0] sig; for an 8b signal.
Declaring reg [8:1] sig; or even reg [1008:1000] sig; gives the same value with sig = 1; $display("sig=%d", sig);
What's the purpose of defining them like that? Is there any disadvantage on calculation(mismatch)? Especially when used with other signals starting from 0.
It depends on the logic you want to create that addresses each individual bit (you might want to read this article on Big-Endian versus Little-Endian. If you don't need to select individual bits, then the ordering and start bit is completely arbitrary.
If you are designing a positioning system, then it might even make sense to have negative indexes.