Even in Apple land M1 isn't the first with unified memory - pretty much all intel on-chip GPU (Sandy Bridge and newer) count - it was even a reason for driver issues early in intel's new dedicated GPU lineup, as the drivers expected unified memory - but M1 is essentially modification of an iPad chip, and you can see "unified memory" there going all the way back to first chip Apple bought from Samsung to power iPhone 2G
You were likely only using Intel systems then. AMD systems have had iGPUs capable of light gaming for a very long time. It took Intel a long time to get to that level, after M1 (2020).
