C64 had a 1mhz 6502 and had way better speech in the form of SAM (software automated mouth). The c64 had a real sound chip (SID, arguably the best of its peers), but SAM did not use it except as a PWM output - it did the formant synthesis in software, and used the SID only to output the resulting 4-bit waveform.
(Which is 3 bits more than the ZX spectrum had... Or the PC effectively until 1990 or so when sound blaster became ubiquitous)
Does anyone have any links/info on the algorithm used in SAM? I remember playing with it as a kid on my friends C64 and then trying to figure out how I could make my own version of it on my obscure (in my part of the world, at least) SpectraVideo https://en.wikipedia.org/wiki/SV-318 using only BASIC "Play" commands. Needless to say, I failed miserably and have been wondering about SAM ever since!
(Which is 3 bits more than the ZX spectrum had... Or the PC effectively until 1990 or so when sound blaster became ubiquitous)