\documentclass[border=3pt,pstricks]{standalone}
\usepackage{amsmath,pstricks,graphicx}
\newsavebox\IBox
\savebox\IBox{\scalebox{15}{%
	\raisebox{\depth}{%
		$\displaystyle 128\sqrt{{}_e980}$}}}

\begin{document}

\begin{pspicture}(\wd\IBox,\ht\IBox)
	\rput[bl](0,0){\usebox\IBox}
\end{pspicture}

\begin{pspicture}(\wd\IBox,\ht\IBox)
	\psclip{\psframe[linestyle=none,dimen=middle](\wd\IBox,0.49\ht\IBox)}
		\rput[bl](0,0){\usebox\IBox}
	\endpsclip
\end{pspicture}

%\begin{pspicture}(\wd\IBox,\ht\IBox)
%	\psclip{\psframe[linestyle=none,dimen=middle](0,0.49\ht\IBox)(\wd\IBox,\ht\IBox)}
%		\rput[bl](0,0){\usebox\IBox}
%	\endpsclip
%\end{pspicture}
\end{document}