Kind of. A lot of the GC support in the Symbolics 3600 architecture is on the Microcode level (current CPUs usually don't have such operations in Microcode). The word size of the CPU is 36bit. The CPU operations don't deal with the type and gc tags on the instruction level, this is done on the Microcode level. Things like "invisible pointers" are also dealt on the Microcode level.

Ephemeral GC, concentrates on garbage collecting objects in RAM: For example every memory page has a page tag, which marks it modified or not. The ephemeral GC uses this to scan only over changed pages in memory. The virtual memory subsystem keeps a table of swapped-out pages pointing to ephemeral pages. The EGC can then use this information...