Motorola 68451

It supported the mapping of up to 32 memory segments or pages of a variable size from logical to physical addresses.

With the earlier MC68000, this was not possible due to the way the MC68000 treated memory access errors, i.e. processor state could not always be properly restored after a page fault; two MC68000s would be required, with the main CPU pausing when it got a memory access error, and the other CPU servicing the page fault.

[2] The limitation to 32 segment table entries per MMU made systems based on a MC68010 and a MC68451 slow, as they often had to modify the segment table due to its small size.

Motorola made a single-board computer module that demonstrated the combination of 68010 and 68451 for applications requiring virtual memory.

Others (e.g. Sun Microsystems, Convergent Technologies) used their own proprietary MMUs instead of the MC68451.