Cylinder 1024

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At boot time the BIOS of many PCs can only access the first 1024 cylinders (0 to 1023) of a hard disk as the BIOS, in Interrupt 13h, uses CHS addressing. CHS addressing only defines 10 bits for the cylinder count (2^10=1024).

This is a problem for operating systems on the x86 platform as the BIOS must be able to load the bootloader and the entire kernel image into memory. Both of these must, therefore, be located on the first 1024 cylinders of the disk.

Older versions of Microsoft Windows resolved this by necessitating that the operating system was installed to the first partition. Because of this bug, users of the Linux operating system have traditionally created a /boot directory to reside within the first 1024 cylinders of the disk, containing little more than the kernel and bootloader.