Western Digital says it has developed a technique that provides more usable space out of a given hard drive capacity. Known as Advanced Format, it reduces the amount of overhead for each data sector by pooling together information. Instead of requiring a single Sync/DAM header and ECC (error correction) block for each sector, it would create much larger 4KB sectors that use one set of each header....
Source : http://www.electronista.com/articles/09/12/11/wd.a...
Source : http://www.electronista.com/articles/09/12/11/wd.a...