It's pretty much the same thing, except that all the memory mapping logic has moved from 'custom memory mapping hardware' into the CPU.
https://en.wikipedia.org/wiki/Address_Windowing_Extensions
*: not actually 4GB, because that makes the kernel code harder to write and tends to lead to bad performance and lots of bugs. They could get 2GB max with the default settings and 3GB with a special configuration.
https://devblogs.microsoft.com/oldnewthing/20040812-00/?p=38...