JSI Tip 6312. Windows XP unnecessarily allocates resources to a disabled or missing secondary (slave) IDE channel?

If Windows XP is installed on a computer that uses the National Semiconductor GX2/CS5535 IDE controller chipset, a missing or disabled secondary IDE channel is allocated resources.

Even though the chipset functions correctly, Windows XP does NOT fully supportit. Windows XP does NOT correctly query the channel status and always enables both channels, causing resources to be unnecessarily allocated.

To determine if you have the National Semiconductor GX2/CS5535 IDE chipset:

1. Use the Registry Editor to navigate to:

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetEnumPCI.

2. If the following sub-key exists, you have the National Semiconductor GX2/CS5535 IDE chipset:

VEN_100B&DEV_002D&SUBSYS_002D100B&REV_00.

To workaround this behavior:

1. Use the Registry editor to navigate to:

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass\{4D36E96A-E325-11CE-BFC1-08002BE10318}.

2. Locate the sub-key that represents the National Semiconductor GX2/CS5535 IDE controller and add the following Value Names:

3. After restarting, the unnecessarily allocated resources on a missing or disabled secondary channel will be available to other devices.

NOTE: Mis-typing any of the above can result in an unbootable system.