So, G92 has different texture units (like G84) than G80.
However, I still don't quite see how the original arrangement of the G80 makes sense. Per texture unit, it could do 4 TA and 8 TF (G92/G84 is 8 TA/8TF, HD2900 is 8TA/4TF per unit).
Now, to me the G92 arrangement makes the most sense (same texture addressing capability than what's needed for (bilinear) filtering).
The HD2900 makes a bit less sense (seems like it would only provide a benefit if you use point sampling / fetch4, is this that common?).
But how does the G80 arrangement make sense? What do you use the additional texture filtering capability for? It was said to provide free trilinear (or free 2xAF bilinear). How should that work? You still need 8 texture addresses for trilinear filtering (4 for one mipmap + 4 for another mipmap).
Or were those 4 texture addresses actually 8, but with parameter restrictions which now have been lifted in G92 (so it would actually calculate 8 addresses, but 4 addresses can't be setup independently and are rather a side-product of the other 4 so they can only be used for the same texture (and next smaller mipmap).
Oh, and there's another flaw in those calculations. Obviously, you need to fetch 4 texels for 1 bilinear-filtered output pixel. So you also need 4 times as much texture addresses - where are all these addresses coming from?
However, I still don't quite see how the original arrangement of the G80 makes sense. Per texture unit, it could do 4 TA and 8 TF (G92/G84 is 8 TA/8TF, HD2900 is 8TA/4TF per unit).
Now, to me the G92 arrangement makes the most sense (same texture addressing capability than what's needed for (bilinear) filtering).
The HD2900 makes a bit less sense (seems like it would only provide a benefit if you use point sampling / fetch4, is this that common?).
But how does the G80 arrangement make sense? What do you use the additional texture filtering capability for? It was said to provide free trilinear (or free 2xAF bilinear). How should that work? You still need 8 texture addresses for trilinear filtering (4 for one mipmap + 4 for another mipmap).
Or were those 4 texture addresses actually 8, but with parameter restrictions which now have been lifted in G92 (so it would actually calculate 8 addresses, but 4 addresses can't be setup independently and are rather a side-product of the other 4 so they can only be used for the same texture (and next smaller mipmap).
Oh, and there's another flaw in those calculations. Obviously, you need to fetch 4 texels for 1 bilinear-filtered output pixel. So you also need 4 times as much texture addresses - where are all these addresses coming from?