SAMdiskHelper

If you’ve accessed BDOS-format disks in Windows, you’re probably aware of the need to run with Administrator rights. For security reasons, raw disk devices cannot be opened by normal unprivileged users.

Starting with Windows Vista, processes are launched with basic rights, even if the current user is a member of the Administrators group. To run with elevated rights the user must either manually launch a program by right-clicking and selecting “Run as adminstrator”, or the program’s manifest file must request it. Both result in a somewhat jarring User Access Control confirmation prompt before the program is launched.

This is a problem for both SAMdisk and SimCoupe, which support BDOS-format disks. Always requesting elevation is not a good option, as raw disk access is currently the only feature that requires elevation. This is where SAMdiskHelper comes to the rescue. It runs as a service under the SYSTEM user with full access to all disks, and can selectively provide access to them. The one-time installation still requires elevated rights, but after that the accessing program can be run with normal rights.

For safety, only disks with a recognised BDOS or Pro-DOS signature are exposed as read-write through SAMdiskHelper. Other disks are seen as read-only by code-signed versions of SAMdisk, and completely inaccessible to all other programs. These rules do mean that new media cards will not be recognised before they’re formatted, ideally on the real Atom device you intend to share the disk with.

To use SAMdiskHelper you just need to have it installed. Supported versions of SAMdisk (v3.8.3+) and SimCoupe (from May 2014) will use it automatically if needed.

You can find the download on my normal website.