Why do old emulated games still suffer from slowdown and lag when they run on modern computers?

Question

Why do old emulated games still suffer from slowdown and lag when they run on modern computers?

In: 36

Answer 1

Instruction Set Translation.

If I ask you to read a letter I wrote in your native language you’ll be able to read it fast and without mistakes. If I write it in a language you don’t know, you’ll need to translate it into your language first, and you might make mistakes.

This is the same process that takes places when emulating games. The language of the original game is written in an instruction set the current CPU cannot understand. The translation from one language to another is expensive. This overhead takes more processing powering and can result in slow downs.