Take the fairly popular 25 MHz Quadra 610, add a 25 MHz 80486SX-based IBM-compatibility card, and you have the Quadra 610 DOS Compatible.
This relatively rare variant of the LC 630 includes a DOS card with an Intel 486DX2/66 CPU, although some shipped with a Cyrix 486/70. The DOS Compatibility card can share Mac motherboard memory or use its own dedicated RAM.
Although PC compatibility isn’t a big deal since Apple’s transition to Intel CPUs in 2006, there is a long history of PC emulation and DOS cards that let Macs run PC operating systems and software. Dayna’s MacCharlie was the first solution to the “problem” of PC compatibility.