Each of the official Spectrum 128 models (MkI, MkII, +2, +2A, +3) had hardware bugs and compatibility issues. The 128Ke is an 'ideal' Spectrum 128 that eliminates these bugs and provides maximum compatibility with existing 48K and 128K software. It can be built in hardware by modifying a Spectrum +2A. This reference is based on the Spectrum 128 reference from the comp.sys.sinclair FAQ. The 128Ke is similar to the 48K machine, but with extra memory accessed by paging it into the top 16K of RAM. There are also some timing differences: