If your driver has extreme memory requirements, it might request more memory than the nonpaged pool contains, yet the call to MmAllocateContiguousMemory succeeds. How can this happen?

An undocumented internal feature of MmAllocateContiguousMemory sometimes causes it to look for a consecutive run of physical pages that satisfy a driver's request for more contiguous memory than is currently available in the nonpaged pool. If so, it maps the pages using system page-table entries (PTEs) and returns this mapping to the caller. It's not guaranteed to work this way in the future, but to find out how it works in released versions of Windows, read the Driver Tip on Contiguous Memory.

More Driver Tips: A New Feature on WHDC...

News for Driver Development and Testing

Kernel-Mode "Do Not Call" List
Certain public imports exposed by public header files such as Wdm.h and Ntddk.h are considered obsolete, deprecated, unsupported, or not recommended for use by kernel-mode drivers, usually because safer and more robust alternatives exist.

The Public Import test in the Hardware Compatibility Test (HCT) kit checks a driver for calls to any of these functions and flags each use with an error or warning. Drivers must pass this test without errors to earn the "Designed for Windows" Logo. However, any kernel-mode driver will be more stable and robust if it is designed to avoid calling these functions. For more information, see:

• Recommended Functions for Kernel-Mode Drivers
• Public Import Test Changes in HCT 12 RC

More Kernel Mode Fundamentals...

Increasing Code Coverage during Driver Testing
One of the best ways to find errors in a driver is to exercise more driver code during testing. Drivers commonly include code to handle rare events, such as inadequate resources or unusual failure scenarios. Testing more such code paths before releasing a driver can improve the reliability of the driver in the field. Check out these simple tips for testing more of your driver code.

More Tools for Testing and Tuning...

Device-Class Tips & News

Windows Filtering Platform Developer Day
On August 9 in Redmond, Microsoft is hosting this NDA event to help software developers and architectures learn how to develop on the Longhorn Windows Filtering Platform for accessing the network stack.

If you are unable to attend the WFP Developer Day event but want to sign up for the related beta program, follow the directions on the event site to register and check the option that says you cannot attend.

To provide Microsoft with feedback about your company's needs for interfacing with the Windows network stack, please complete the Windows Filtering Platform requirements survey.

Register Now for Meltdown 2004
The gaming industry: So much to learn, so little time. Participate in two intense days of seminars July 27-28 in Seattle. This event is for graphics developers, software developers, QA testers, Web publishers, and business developers.

Writing WIA Drivers for Windows 64-bit Edition for Extended Processors
What interoperability issues occur-and how are these resolved-when 32-bit applications trying to access 64-bit WIA minidriver UI extensions? Learn the guidelines for scanner and digital camera vendors who want to ensure their devices work on PCs that use the x64 hardware architecture.

More Device Fundamentals - Overview...

Platform Directions for Windows

Coming Soon: Windows Marketplace
Microsoft has announced a new customer value-added Web site and key partner opportunity called the Windows Marketplace.

Windows Marketplace is a comprehensive, easy-to-use shopping and download portal that helps customers discover and purchase third-party software and hardware that works with the Microsoft Windows family of operating systems. Microsoft is working in partnership with leading companies in the shopping and content industry to make the Windows Marketplace a premier destination for Windows-compatible products.

Windows Marketplace complements the Windows Catalog as an additional opportunity for customers who want to purchase Windows-compatible third-party products. The Windows Catalog highlights products built for Windows XP that have earned the "Designed for Windows" logo.

Launch of the Windows Marketplace in the U.S. is planned for the fourth quarter of 2004. Find out more...

More General PC Platform Design and News...

Security and Reliability

Top Ten Security Tips Every Developer Must Know
What are some of the really important issues and the biggest mistakes you should watch out for right now so that you don't compromise your data or your system?

Download the RC2 Preview of Windows XP SP2
You can obtain the current build of the new service pack from the Web. Check this Web site for information about changes in functionality, developer resources, and newsgroups discussions.

Microsoft Security Developer Center on MSDN

More Driver Security and Reliability...

Kits, Tools, and Services

Using Checked Builds of Windows
Driver developers use the checked builds of Microsoft Windows to identify and diagnose operating system-level problems. Review these tips for how to obtain checked builds online and how to use checked builds of Windows.

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