What HDs will be compatible with my mobo.

[texruska]

correct me if I'm wrong, but a Gigabit is 1000 megabits, 8 bits = 1 byte. 1000 / 8 = 125

Isn't it 1,024 megabits? That would make it 128.

[Deleted]

Isn't it 1,024 megabits? That would make it 128.

This is correct.

[Asmekiel]

As used for storage capacity, one megabyte (MB) = one million bytes, one gigabyte (GB) = one billion bytes, and one terabyte (TB) = one trillion bytes.
Total accessible capacity varies depending on operating environment.
As used for buffer or cache, one megabyte (MB) = 1,048,576 bytes.
As used for transfer rate or interface, megabyte per second (MB/s) = one million bytes per second, megabit per second (Mb/s) = one million bits per second, and gigabit per second (Gb/s) = one billion bits per second.

From the Western Digital site.

If 1024 or 1000 is used, depends on where it's used and also on manufacturer.
While the quoted part is true for WD, it may not be true for, lets say, Samsung.

[Deleted]

There are both ways to count: GB versus GiB and that's what's occasionally confusing with, say, a 2TB disk actually containing ~1863 GB of actual empty space as reported by the operating system as 2000 / 1.074 ~ 1863. Generally division by thousands is used for storage space, but not transfer rates, unless the manufacturer wants to inflate their numbers by using the higher number from dividing by 10^x instead of 8^x.

[Cyanotical]

1 = 1 bit
111111111 = 1 byte
1 kilobyte is 1024 bytes, it's not exactly 1000 because 1000 does not divide evenly in a base 2 math system

beyond a KB it's up to the manufacturer whether they want to continue using the base 2 system or standard base 10

if they use base 2 then 1 megabyte is 1024 KB
if they use base 10 then 1 megabyte is 1000 KB