expletive said:
The varying clockspeeds/pipes are for several different reasons.
1) Said chip cannot reach the spec'd speed of given card at given voltage - rather than toss, they create a 'budget' line of cards utilizing these chips at a lower clockspeed.
2) Card prices are not always reflective of chip costs; in order to address different market segments, several tiers of card are created using the same chips, the lower tiers being clocked slower and perhaps with some of the pipelines hardware masked in order to sell more chips/cards. They are of course 'reduced' in performance to justify the price premium on the top-end parts.
3) Die defects can damage pipelines in the GPU. But since the GPU will still function if those pipes are simply deactivated, the maker can utilize them in 'lesser' cards to make sure they don't go to waste.
Numbers 1 through 3 can work in conjunction with each other as well to achieve multiple goals in a single SKU.
For example, I purchased a 6800LE AGP card recently - an NV40 based card that is clocked by default at 300 MHz, has 8 pixel pipes enabled, and 4 vertex pipes. The chip itself though has 16 pipes and 6 vertex pipes.
Towards the end of a generation the chips populating these 'crippled' SKU's tend to get better and better as yields improve (and previous contracts still have to be fulfilled of course). Soooooo, knowing this, I bought the card thinking my chances for unlocking would be good. And indeed they were. Unlocked every single pipe successfully and clocked it up modestly to 325 core (raised memory 100 MHz as well).
If you have AGP and want a cheap upgrade, the Leadtek 6800LE on NewEgg - can't go wrong!
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