The following options for the Developer Dashboard:
On
SharePoint 2010: The Developer Dashboard will always be rendered at the bottom of each page
SharePoint 2013: The Developer Dashboard icon will always be displayed at the top right corner.
It will not be appended to each page. Off
SharePoint 2010 & 2013: The Developer Dashboard will not be available
OnDemand
SharePoint 2010: The Developer Dashboard will only be appended to
a page after clicking on the icon in the ribbon
SharePoint 2013: This mode is not available in 2013 since it reflects the behavior of On now
On
SharePoint 2010: The Developer Dashboard will always be rendered at the bottom of each page
SharePoint 2013: The Developer Dashboard icon will always be displayed at the top right corner.
It will not be appended to each page. Off
SharePoint 2010 & 2013: The Developer Dashboard will not be available
OnDemand
SharePoint 2010: The Developer Dashboard will only be appended to
a page after clicking on the icon in the ribbon
SharePoint 2013: This mode is not available in 2013 since it reflects the behavior of On now
$svc = [Microsoft.SharePoint.Administration.SPWebService]::ContentService
$dds = $svc.DeveloperDashboardSettings
$dds.DisplayLevel = "On"
$dds.Update()