The Amiga had both chip and fast RAM, the latter was only accessed by the CPU. Not too different from GPU coprocessors today sharing unified access to some fra

The Amiga had both chip and fast RAM, the latter was only accessed by the CPU. Not too different from GPU coprocessors today sharing unified access to some fraction of system memory. "Complicated caching architectures" use coherence protocols to ensure that things are kept consistent when required. *nix-like systems would have come with a lot of overhead back then. Perhaps you could've had MMU-based sandboxing and virtual memory as an optional feature, so that old applications and games could still rely on bare-metal hardware access.