Dell OptiPlex GX1 Reference And Installation Manual page 64

You cannot manually enter a value; you must choose a setting from the list. If
there is only one setting listed, no other settings are available.
The setting that you select may affect the resources available. For example, if you
are offered the Disabled option and select it, all resource values are blank, indicat-
ing that a disabled setting uses no resources.
For example, when you click the value under DMA, the Options button changes
to the DMA Options button. When you click this button, a smaller dialog box
appears. By clicking the down arrow next to the current resource value, you can
display a list of the available values for the resource.
Choose the desired value and click OK. The value you selected is displayed under
the resource heading in the Configuration Settings dialog box.
The Options button is disabled if no alternative values are available for the
selected resource.
NOTE: If you change one or more resource values using the Options button and
later change the setting in the Configuration Choice box, the changes that you
made to the resource values are overwritten by the default values for the new
configuration choice.
3-8 Dell OptiPlex GX1 and GX1p Mini Tower Managed PC Systems Reference and Installation Guide