You may have wondered why we use the notation MiB, MB, GiB, and GB to represent the capacity of an on-board memory device. For example the Genesys 2 has 1 GiB of DDR3 memory while the Nexys Video has 512 MB of DDR3 memory. The mixed use of the notations may frustrate you but this post aims to quell any distress you may have about this topic.
The SI prefixes are for strict use with powers of 10, not powers of 2 as used by computers. To solve this the International Electrotechnical Commission (IEC) came up with a new prefix standard for powers of 2, known as binary prefixes. The solution was to add an “i” between the initial letter and the “B”. Full prefixes were also defined. As per the specification of the prefixes, the power of 2 prefix counterpart to Kilo- is Kibi-. The prefix Kilo- stands for 10^3 while Kibi- stands for 2^10. This means that a Kilobyte is 1000 bytes while a Kibibyte is 1024 bytes. This might not seem like a big difference but when it gets to Gigabytes versus Gibibytes the difference becomes much more noticeable. The full prefix chart is in the image below.
From the table, one can see that a Gibibyte is 1,073,741,824 bytes or 73,741,824 bytes more than a Gigabyte so the Genesys 2 has 1.073 GB of DDR. Also the 512 MiB on the Nexys Video can be converted to 536 MB. Since the memory world has yet to convert to the newer, more accurate notation, Digilent uses MB and MiB interchangeably. So if you see MB on any of our sites and are confused, keep in mind it means the same thing as MiB. If you find yourself questioning any of the notations or units that we use, feel free to contact us through the forum.