With the new Motorola 68030 processor came the Macintosh IIx in 1988, which had benefited from internal improvements, including an on-board MMU. It was followed in 1989 by the Macintosh IIcx, a more compact version with fewer slots  and a version of the Mac SE powered by the 16 MHz 68030, the Macintosh SE/30. Later that year, the Macintosh IIci, running at 25 MHz, was the first Mac to be "32-bit clean." This allowed it to natively support more than 8 MB of RAM, unlike its predecessors, which had "32-bit dirty" ROMs (8 of the 32 bits available for addressing were used for OS-level flags). System 7 was the first Macintosh operating system to support 32-bit addressing. The following year, the Macintosh IIfx, starting at US$9,900, was unveiled. Apart from its fast 40 MHz 68030 processor, it had significant internal architectural improvements, including faster memory and two Apple II CPUs (6502s) dedicated to I/O processing.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What was the first Mac to be "23-bit clean"?
unanswerable