Because 32-bit device drivers cannot be used with the 64-bit operating system, these drivers must be recompiled as 64-bit objects. Moreover, the 64-bit drivers need to support both 32-bit applications and 64-bit applications. All drivers supplied with the 64-bit operating environment support both 32-bit applications and 64-bit applications. However, the fundamental driver model and the interfaces supported by the DDI do not change. The principal work is to clean up the code to be correct in an LP64 environment. See the Writing Device Drivers manual for more information.