Well, MIPS is still in widespread use in wifi hardware, and POWER is being resurrected for a scale-up way to deal with a growing database, considering the current generation scales higher at about a similar pricepoint than a 4-socket Intel machine. So I am not sure what the past tense is supposed to mean, if it denotes the architectures to no longer compromise a significant part of world-wide (say DRYSTONE) MIPS, or their lack of use where they are good at (false).
SPARC and MIPS for example worked like this, and server POWER chips had a hashed page table that many OSes populated lazily, effectively treating it like a (more efficient) software TLB.