I don't fully understand your post TBH. I'm not saying that the HD5770 is the replacemet for the 4890. All I'm saying is that the only difference between those two cards, specs wise, is the memory bandwidth. Both have 800 SP, 16 ROPs and 40 TMUs clocked at 850 Mhz, so in theory they should perform the same if the memory was fast enough in both cards. IDK. Maybe it's not the memory. For the HD5870, which is also slower than what the specs suggest, I have said in the past weeks that it could be the setup engine/thread dispatcher that has not been improved. I don't think that is the case in the HD5770, because I'd think that the thread dispatcher is the same in every HD5xxx card*, so it should be more than enough for the HD5770. In the case of the HD5770 I just think it's the memory, but I'm waiting those benchies. I like speculating and then seing actual empirical work confirm or destroy my theories. * It makes sense IMO. Same unit for all means less R&D and those units take up very little die area compared to other units, so including acomparatively big/fast dispatcher doesn't increase the price of smaller chips.