The bold small caps don't work with mathpazo font. I am a issue with this macro for take in upper case a bold text : the text is never in upper case.

\documentclass{minimal}
\usepackage[sc,osf]{mathpazo}

\newcommand\normal{\fontseries{\ifx\f@series\bfdefault\then m \fi}\selectfont}

\makeatletter
\DeclareRobustCommand{\mytextsc}[1]{%
    \ifx\f@series\bfdefault%
 \uppercase{#1}%
    \else
 {\scshape #1}%
    \fi
}
\makeatother

\begin{document}
\textbf{This is a bold \mytextsc{upper case} text.}

This is a \mytextsc{small caps} text.

\end{document}