Great question actually! BOINC as a platform can run on any hardware, but individual projects have specific hardware requirements. Like you mentioned, some projects need a lot of RAM, but fortunately most don't. The most prominent split is between CPU and GPU projects. For example, SRBase only runs on CPUs, while the vast majority of Moowrap runs only on GPUs.

No matter the hardware (bar the super extreme), there will be a BOINC project you can contribute to. Hell, there are members of the Gridcoin community who have written entire articles on setting up a Raspberry Pi Gridcoin farm.