Beamer two column overlay display aligned equations right column first then left

Question

I am trying to setup an overlay for a frame where I would like to display the list of equations inside aligned env inside the right column first, followed by list of equations inside aligned env inside the left column.

What I have tried below: Following some searches, I found you can use \onslide to overplay right column before left, and there is a work around which I have included to allow aligned env to use /pause for overlays. However, the two things together does not seem to work.

\documentclass{beamer}
%allow for pause inside aligned
\def\pdftex@driver{pdftex.def}
\ifx\Gin@driver\pdftex@driver
\def\pgfsys@color@unstacked#1{%
    \pdfliteral{\csname\string\color@#1\endcsname}%
}
\fi
\begin{document}
\begin{frame}
\begin{columns}
\onslide<2->{
\column[t]{0.5\textwidth}
\[
\begin{aligned}
equation 4 &= display 4th \\ \pause
equation 5 &= display 5th \\ \pause
equation 6 &= display 6th \\ \pause
\end{aligned}
\]
}
\onslide<1->{       
\column[t]{0.5\textwidth}
\[
\begin{aligned}
equation 1 &= display first \\ \pause
equation 2 &= display second \\ \pause
equation 3 &= display third \\ \pause
\end{aligned}
\]
}
\end{columns}   
\end{frame}
\end{document}

Answer 1

There are two problems in your example:

1. you want the left column to be displayed from the 4. slide, so you would have to use \onslide<4->{ and not \onslide<2->{
2. but than you have still the problem, that the pauses in the left column come before the right column, so the items 4 to 6 are revealed first, even if they are invisible due to the \onslide

For this complicate arrangement, manual overlays gives the most flexibility:

\documentclass{beamer}
%allow for pause inside aligned
\def\pdftex@driver{pdftex.def}
\ifx\Gin@driver\pdftex@driver
\def\pgfsys@color@unstacked#1{%
    \pdfliteral{\csname\string\color@#1\endcsname}%
}
\fi
\begin{document}
\begin{frame}
\begin{columns}
\begin{column}[T]{0.45\textwidth}
\[
\begin{aligned}
\onslide<4->{equation 4 &= display 4th \\} 
\onslide<5->{equation 5 &= display 5th \\} 
\onslide<6->{equation 6 &= display 6th \\} 
\end{aligned}
\]
\end{column}  
\begin{column}[T]{0.45\textwidth}
\[
\begin{aligned}
\onslide<1->{equation 1 &= display first \\} 
\onslide<2->{equation 2 &= display second \\} 
\onslide<3->{equation 3 &= display third \\} 
\end{aligned}
\]
\end{column}
\end{columns}   
\end{frame}
\end{document}