If you've got a 1980's Macintosh (such as the Macintosh II) with more than 8MB of RAM, make sure to install Mode32 as all models from the 1980's (68K) came with a 24-bit addressing ROM, which can only reach up to 8,388,608 bytes (8MB) and nothing higher than that.  All Macs starting from 1993 came with a 32-bit clean ROM which pushed the RAM addressing limit so high (4GB) that most Mac models could not even physically reach it until the very last PowerPC Mac models.

Read more on this topic over at Low End Mac: https://lowendmac.com/2015/32-bit-addressing-on-older-macs/