I'm pretty sure that by Ghash, people mean Gigahash. 1 Gigahash = 1000 Megahashes, so the first one.
As binary doesn't apply, that's correct.
If it was memory/HDD storage, then it would be 1024.
Remember... there is a difference between a MB and a Mi
B. Memory is usual in X
iB, while storage is normally in X
Knuth wishes it weren't so:
What is a kilobyte?
Many people (and many online dictionaries) claim that a kilobyte (kB or KB) is 2^10 bytes, and that a megabyte (MB) is 2^10 kilobytes, etc.
I'm a big fan of binary numbers, but I have to admit that this convention flouts the widely accepted international standards for scientific prefixes.
Therefore I propose a simple way to resolve the dilemma and the ambiguity: Let us agree to say that
2^10 bytes is a large kilobyte, abbreviated KKB;
2^20 bytes is a large megabyte, abbreviated MMB;
and so on up the line: Large giga-, tera-, peta-, exa-, zetta-, and yottabytes are GGB, TTB, PPB, EEB, ZZB, and YYB, taking us up to 2^80. (Notice that doubling the letter connotes both binary-ness and large-ness.)
These proposals were motivated by the suggestions in 1995 of IUPAC-IDCNS (the International Union of Pure and Applied Chemistry's Interdivisional Committee on Nomenclature and Symbols), which were extended by IEC TC 25 (Technical Committee 25 of the International Electrotechnical Commission), chaired by Anders J. Thor. According to those committees, 2^20 bytes should be called a "mebibyte" and abbreviated MiB; 2^40 bytes should be called a "tebibyte" and abbreviated TiB; etc. The members of those committees deserve credit for raising an important issue, but when I heard their proposal it seemed dead on arrival --- who would voluntarily want to use MiB for a maybe-byte?! So I came up with the suggestion above, and mentioned it on page 94 of my Introduction to MMIX. Now to my astonishment, I learn that the committee proposals have actually become an international standard. Still, I am extremely reluctant to adopt such funny-sounding terms; Jeffrey Harrow says "we're going to have to learn to love (and pronounce)" the new coinages, but he seems to assume that standards are automatically adopted just because they are there. Surely a huge number of standards for other computer things, like networking protocols, have been replaced by better ideas when they came along. Thus I hope it still isn't too late to propose what I believe is a significantly better alternative, and I still think it unlikely that people will automatically warm to "mebibytes". Indeed, the last time I looked (June 28), names like "mebibyte.com" were being offered for sale but with no takers! I might, however, want to buy into a name like mmegabyte.com... And even in the unlikely event that mebibytes do catch on, MMB surely wins over MiB as their abbreviation. [See also the discussion by Kevin Walsh.]