1:1 means 'real size' or 'actual size'. In other words, if a wall of a house is 5 feet long, you always construct it as 5 feet long.
Only for printing, a scale factor is applied to your drawing (without changing the actual drawing contents).
To set the scale to 1/8"=1', please proceed as follows:
- Create a new drawing: File - New
- Open the drawing preferences dialog: Edit - Drawing Preferences
- Navigate to: General - Drawing Unit
- Set the Drawing Unit to 'Inch'
- Set the Paper Unit to 'Inch'
- Navigate to: Dimension - Dimension Settings
- Set the Label Format for Linear Dimensions to 'Architectural' (optional, but usually recommended for architectural drawings)
- Navigate to: Printing - Page
- Set the Scale to: 1/8" = 1'-0"
- Click 'OK'