I’m still disappointed that you can’t boot a modern processor with its 8MB of L2 cache and run Windows 95 entirely in cache. Stupid requirements to have a backing store.
I think if you flip the right MSRs, you can actually run in this mode on Intel. BIOSes used to do DDR3 calibration in this mode, and needed to run a core DRAM-less to do it.
AMD Zen platforms have always put that functionality (ironically) in the secret platform security coprocessor.
