\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}