There is an unfortunate side effect of large pages. Each page (whether large or small) must be mapped with a single protection that applies to the entire page (because hardware memory protection is on a per-page basis). If a large page contains, for example, both read-only code and read/write data, the page must be marked as read/write, which means that the code will be writable. This means that device drivers or other kernel-mode code could, as a result of a bug, modify what is supposed to be read-only operating system or driver code without causing a memory access violation. If small pages are used to map the operating system’s kernel-mode code, the read-only portions of Ntoskrnl.exe and Hal.dll can be mapped as read-only pages. Using small pages does reduce efficiency of address translation, but if a device driver (or other kernel-mode code) attempts to modify a readonly part of the operating system, the system will crash immediately with the exception information pointing at the offending instruction in the driver. If the write was allowed to occur, the system would likely crash later (in a harder-to-diagnose way) when some other component tried to use the corrupted data.