What needs to be done to enable 32 bit I/O transfer mode for (E)IDE disks, on a system running a 2.4
series Linux kernel?

A.
The Linux kernel must be recompiled.

B.
The sysctl utility must be used.

C.
The hdparm utility must be used.

D.
This feature isn’t supported in 2.4 series kernels.

E.
This feature is enabled by default in 2.4 series kernels

Explanation:
hdparm provides a command line interface to various hard disk ioctls supported by the stock Linux
ATA/IDE device driver subsystem. Some options may work correctly only with the latest kernels.
-c Query/enable (E)IDE 32-bit I/O support. A numeric parameter can be used to enable/disable 32-bit
I/O support: Currently supported values include 0 to disable 32-bit I/O support, 1 to enable 32-bit
data transfers, and 3 to enable 32-bit data transfers with a special sync sequence required by many
chipsets. The value 3 works with nearly all 32-bit IDE chipsets, but incurs slightly more overhead.
Note that “32-bit” refers to data transfers across a PCI or VLB bus to the interface card only; all
(E)IDE drives still have only a 16-bit connection over the ribbon cable from the interface card.