ATA in Win2K
When Win2K first shipped, Microsoft's default atapi.sys driver included support for ATA data-transfer modes up to and including UDMA/66, which was the fastest standard in widespread use. However, Microsoft chose not to enable the most aggressive mode (UDMA/66) as the default setting on many systems that had Intel-based ATA chipsets (which are the most commonly implemented chipsets in modern PCs). Ostensibly, Microsoft made this choice to prevent data corruption and similar problems with certain disk, controller, and driver combinations. However, few people knew about or understood Microsoft's decision. Then, Microsoft published "HOWTO: Enable UDMA66 Mode on Intel Chipsets" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q247951), and users became aware that Win2K wasn't automatically enabling the UDMA/66 setting. The article shows users how to remedy the situation by modifying the system registry. However, the article provides no guidance about important specifics such as which Win2K service packs, Intel chipsets, and disks this default configuration setting affects. Also, the article fails to address how the setting relates to UDMA/100 or non-Intel chipsets.
The situation became even murkier when Microsoft released another ambiguous ATA-related article: "Support for ATA 100 (Mode 5) in Windows 2000" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q260233). This article states that Win2K Service Pack 2 (SP2—or a pre-SP2 hotfix) addresses Win2K's failure to support ATA/100 (aka DMA Mode 5). Unfortunately, this article also lacks crucial information about the problem, such as which ATA chipsets it affects (i.e., Intel, non-Intel, or both), how the problem relates to the aforementioned ATA/66-related fix, and what service pack levels the pre-SP2 hotfix version of the remedy affects (i.e., base release or SP1). Even today, Microsoft provides no concrete guidance about these topics, and although you can find relevant articles on the Internet, those articles come primarily from non-Microsoft sources and are based on anecdotes rather than hard facts.
If you have the precise type of system that Microsoft is targeting in its articles, then the recommended registry modification and SP2 installation might be all you need to enable ATA/100 support on your system. If the article's tips don't apply to your system, the best-case scenario is that the modifications will have no effect; the worst-case scenario is that the modifications will cause system errors and data corruption.
Third-Party Drivers to the Rescue
None of the aforementioned Microsoft articles mention that these ATA-support problems are specific to the default atapi.sys driver, nor that users might be better served by using third-party drivers specific to the chipset in use. Third-party drivers often circumvent most of the aforementioned problems and take full advantage of the chipset's capabilities. In many cases, the drivers' installation routines automatically configure the system (including any necessary registry settings) to properly take advantage of the fastest ATA modes that the chipset supports. Unfortunately, although most system and ATA chipset manufacturers provide drivers for their ATA controllers, most users are either unaware of their existence or fail to install them.
One example of a third-party ATA chipset driver is the Intel Ultra ATA Storage Driver, which you can obtain from http://support.intel.com/support/chipsets/storagedrivers/ultraata. This site not only contains Ultra ATA drivers for Win2K and other Windows OSs—with full support for all ATA data-transfer modes—but also contains a chipset-configuration utility that helps you ensure that Win2K properly recognizes your ATA chipset. Other chipset manufacturers, such as VIAHardware.com, also produce custom Win2K drivers for their controllers. A final benefit of third-party drivers is that some of them include utilities to not only properly configure and enable advanced ATA data-transfer modes but also identify which PIO or DMA modes various ATA channels and devices are using. Win2K attempts to provide similar information—for example, you can go to Device Manager, open the ATA channel's Properties dialog box, and select the Advanced Settings tab. However, Win2K's information lacks details and in some cases—such as in the hotfix discussed in the Microsoft article "Device Manager Lists ATA-100 Device Incorrectly as Using PIO Instead of UDMA" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q269555)—Win2K displays incorrect information.
To maximize the manageability, reliability, and performance of your ATA devices in Win2K, you'll need to do a little research and legwork. Remember that each system is different, with different controllers, chipsets, disk brands and models, ATA specifications, and drivers. Ensuring that you have the proper mix of system hardware, OS updates, and—if necessary—third-party drivers can be a complicated job. With a bit of elbow grease, however, you should be able to get your ATA devices operating at peak performance.