advanced format, aligned

since new disks exceed the old sector / heads / cylinder specs the makers have resorted to this “cheat”:

sec = 255
heads = 63

always, which is the max the parameters allow, and you vary the cyl number to increase its size (e.g. 243201 cyl for a 2000GB disk)

now this leads to having the first user sec (after the bootsector, number zero!) to be at 255 x 63 sectors on cyl 1 => sector 16065 , which is NOT a multiple of 8, therefore NOT aligned, and all that follows is slow access

move the beginning to the 64th sector, and the first partition starts at 255 x 64 => sector 16320 (which is 8 x 2040 ), and use for partitions’ cylinder count a multiple of 8
(that’s a “math cheat” to ensure the sector number will always be divisible by 8, since “anynumber x anothernumber x 8” will always be divisible by 8)

in my case a WD20EARX the write speed went from 43MBs to 76MBs, read from 64MBs to 72MBs for a contingous 2GB file – wth an old PCI-SATA150 controller

most important in all of this is that a filesystem cluster (4k size with NTFS, and ext3 linux) fits perfectly inside a physical 4k unit on the disk – and even when you still use 512 byte sectors once it’s aligned that improves speed, since you read 8 of those in one go