Casio fx-991EX vs Hp 50g speed difference

[gomefun2]

I know for me personally when I solve the exponential integral on the TI-nspire it takes a really long time depending on the value chosen for x:

https://en.wikipedia.org/wiki/Exponential_integral

When I program it into my WP34s (real hardware) it takes probably 1/20th the time. This is because I use an algorithm specifically designed to solve the exponential integral quickly.

I found in my personal research in regards to integrals of exponential functions that algorithms that are really good at them are generally worse at other types of integrals and vice versa. The HP 50g probably just uses an algorithm that is not very efficient at solving integrals of exponential functions. You could test this by programming the 50g with your own custom solver that is good with exponentials, I'm sure it would be must faster.