It's fairly common practise to make 1 high spec version of a chip and then lock parts of it to make the budget versions.
For example, the AMD Phenom "Toliman" (X3) and "Kuma" (X2) CPUs are just "Agena" (X4) chips with 1 or 2 cores disabled. (http://en.wikipedia.org/wiki/List_of_AMD_Phenom_microprocess...)
When the X4 chips are manufactured they are tested, and if a core fails any tests it is just locked and sold as an X3/2. This increases manufacturing yields by making use of some of the failures. Of course as there is also higher demand for the lower-middle spec CPUs, sometimes perfectly working chips are restricted to meet the supply requirements for each market space.
And of course, often the different clock speeds are really just the same chips with locked multipliers.
I believe Sony followed a similar procedure for the PS3 cell CPUs - http://en.wikipedia.org/wiki/Cell_%28microprocessor%29#Comme...
But of course, for very good reason: it allows the computer to remain on for 10 hours instead of 10 minutes. Power saving is a big deal these days, but back in the 386 days, nobody cared (and 4.77MHz processors were not exactly power-hungry either).