Windows 98Me Compatibility Notes

Windows 98/Me Compatibility Notes

In addition to the horrible problem with KeWaitXxx functions described in an earlier sidebar and the fact that KeReadStateEvent isn t supported, note the following additional compatibility issues between Windows 98/Me on the one hand and Windows 2000/XP on the other.

You cannot wait on a KTHREAD object in Windows 98/Me. Attempting to do so crashes the system because the thread object doesn t have the fields necessary for VWIN32 to wait on it.

DISPATCH_LEVEL in a WDM driver corresponds to what is called interrupt time in a VxD driver. Every WDM interrupt service routine runs at a higher IRQL, which means that WDM interrupts have higher priority than non-WDM interrupts. If a WDM device shares an interrupt with a VxD device, however, both interrupt routines run at the WDM driver s DIRQL.

WDM driver code running at PASSIVE_LEVEL won t be preempted in Windows 98/Me unless it blocks explicitly by waiting for a dispatcher object or implicitly by causing a page fault.

Windows 98/Me is inherently a single-CPU operating system, so the spin lock primitives always just raise the IRQL. This fact, combined with the fact that nonpaged driver code won t be preempted, means that synchronization problems are much less frequent in this environment. (Therefore, do most of your debugging in Windows XP so you ll trip on the problems.)