I can't give any great technical insight on this question, but I'll tell you what I can. That issue is due to the fact that the two parts come from two different places. NVIDIA produces the GPU (I hate NVIDIA acronyms btw) to run at a certain speed. They then determine what speeds (GPU and RAM) get the performance they want for each grade of vid card (Ti4200, MX440, etc.). When they're producing their GPUs, they use the ones that come out "better" for the higher grade cards, and thus, the higher clocks. For the GeForce 3, the Ti200 and the Ti500 are mostly identical, but the 500 was tested more. However both have their limits. If you'll notice, while the Ti500 will consistently get higher SPEEDS than the Ti200 in overclocks, it doesn't get as high of an INCREASE in speeed as the Ti200. For instance, I think that the Ti200 can get to around 250, an increase of 75MHz over stock speeds, while the Ti500 can get to 270, and increase of 30MHz over stock speeds.
Now you're asking yourself, "How does this explain the RAM?" If you remember, we're running DDR RAM. I THINK, THOUGH I AM NOT SURE that the RAM itself is only being stressed half as much as its rating. Not knowing exactly how DDR works, I'm not entirely sure how this would come about, but I'm almost positive that this is the biggest factor here. If you'll notice, dr jones bsc claimed an overclock of 35/70 on the GPU/RAM respectively. So, when overclocking, I suggest going in increments of 5/10 rather than 5/5. Also, as I mentioned before, the manufacturers actually put the RAM on the card and can choose any RAM that at least meets the specifications of each particular card. For the Ti500 that would be 4ns RAM, while the Ti200 would need only 5ns RAM. In case you don't know, the ratings translate into frequencies in the following way: 1second / "X" nanoseconds = Hz Rating. Many manufacturers (I'm almost positive your Gainward is one of them) put higher-rated (or lower, depending on whether you're measuring MHz or ns) RAM on their cards so that the enthusiasts buying them will be able to clock their cards just a little bit faster than everyone else, giving them an advantage in that market. Or, they just buy a bunch of RAM for the GF3 Ti line, getting a decent bulk price, and put the same RAM on the Ti200 as the Ti500, making the 200 rated to at least 500MHz. Therefore your enthusiasts are happy at a lower cost.
I can tell you this for sure: you will see the best gains IN MOST INSTANCES when you overclock at a rate of 5/10. However, this wasn't true with the GF2s. Though I have no idea why, I know that overclocking the RAM gave the GF2s their biggest increases in speed. After pushing the RAM to its limit, pulling the GPU up to speed gave very little incremental performance.
To answer the other question from ZueSueZ, the GF3 Ti500 was 240/500 while the Ti200 was 175/400. Go to
http://www17.tomshardware.com/graphic/02q2/020418/index.html for a complete rundown of all cards.
She said "I love a man in tight jeans" and I said "They're not supposed to be tight I just got fat."