What is the difference between 8600GT and 8600GTS gpu

From what I've seen both seems to be the same gpu placed on cards with different memory clocks.

Now is there a difference in hardware justifying the use of different core clock speeds?

And what about different shader clock speeds?

sorry for the typo of course it is 8600GT vs 8600GTS.

Every launch article should answer this question. The GT has a lower clocked core, lower clocked memory, and therfore is slower and uses less power. Less power means no need for an external power connector, which in turn will limit GT overclocking. Higher core clocks need better cooling. Faster memory chips are more expensive. Otherwise they are the same.