Not all of them. In recent years, virtually all arcades have been powered by standard gaming PCs (see for example the infamous Half-Life 2 arcade). In the past, it wasn’t unheard of for some arcades to have nearly identical hardware compared to home consoles. The Neo Geo arcade for example is running the exact same code as the home console (although in this case, the arcade came first). There have also been edge-cases, like the Namco System 11, which is using only slightly modified PS1 hardware (primarily in the sound department) in order to drive down costs.