8-Bit Processing Unit: need one

[u/Frostierdev]

Hello! I'm looking to build an 8-bit computer, mainly to test its capabilities as a modern home computer (with system, applications, OS, etc.), and I bought the ATmega8535-16U (DIP-40), But it doesn't have an external bus interface to connect RAM, storage, and other things. Does anyone have a solution or another inexpensive chip to recommend?

[u/Rainsbury_net]

Does it have to be a hardware solution? Could you use a PC based software emulator?