How to Add More Than Two IDE or ESDI Drives in Windows NT

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WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

Most new computers come with two built in IDE controllers. Each controller (or channel) can handle two IDE Hard drives. This procedure should only be necessary if you are trying to add a third or higher IDE or ESDI controller or if your secondary IDE or ESDI controller is at a non- standard memory address. If the drive is at a non-standard address, use the following procedure to add the correct address to the Windows NT registry. The registry key name in this case would be either 1 or 2.

NOTE: The information in this article applies only to Intel x86 architecture computers.

To add support for three or more IDE or ESDI controllers in Windows NT, follow these steps:

1. Start Registry Editor (Regedt32.exe), and then locate the following registry key:
   

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Atdisk

2. On the Edit menu, click Add Key, and then create the following key:
   

   Key Name: PARAMETERS
   Class: <blank>

3. Open the PARAMETERS key that you created in Step 2.
4. On the Edit menu, click Add Key, and then create the following key:
   

   Key Name: <number>
   Class: <blank>

   
   where <number> is the number of the additional drive, such as 2 for the third drive. For each additional drive, increment the Key Name by 1. In general, you must specify the starting parameter as 2 or higher. This prevents a conflict with the primary or secondary controller that most BIOSs support.
5. Open the key that you created in step 4.
6. On the Edit menu, click Add value, and then add the following values:
   

   BaseAddress
   -----------
   This is the physical address of the Data register for the controller.
   
   DriveControl
   ------------
   This is the physical address of the drive control register of the controller. Often this is 0x206 off of the BaseAddress register.
   
   Interrupt
   ---------
   This is the interrupt that the controller will use.
   
   NOTE: Set the Data Type of all three entries to REG_DWORD.

7. Quit Registry Editor.

Here is what a sample registry entry looks like for adding a Quantum EZ hard disk onto a COMPAQ 486/33L. This computer has a simple ESDI drive as its primary controller.


NOTE: On an R4000 ARC computer, you should not have to add anything if you configure the IDE adapter for the 0x1f0 or 0x170 memory address.