I thought I knew a lot about 68k processors, but "88k" is new to me. It turns out to be the Motorola 88100¹, which was used in Unisys servers running Unix.
Fun fact - the 88k was designed by Mitch Alsup, who also designed SPARC CPUs for Ross, x86s for AMD and others. He is retired, but still active in the comp.arch Usenet newsgroup.