Because the HD6900 series cards use the VLIW4 architecture while all the rest of the HD5/6 and low end parts of 7/8 use VLIW5. The VLIW4 architecture is very similar to that of VLIW5, which is why it got supported so quickly, however it is nowhere near as optimized as only the HD6900 cards had it and as such they are of a much lower priority and the small public testing pool for them doesn't help things. Theres maybe a few hundred thousand(wild guess) HD6900 cards in existence, while theres actual millions of VLIW5 based GPUs out there. They are even in all APUs that are pre Kaveri and Kabini as those series added GCN based GPUs.
Originally Posted by dungeon
The fastest VLIW5 cards are the HD5870 and HD6870, both perform very closely, the HD5870 having an edge in double precision OpenCL and having had an Eyefinity 6 edition w/ 6x mini Display Port outs and double the vRam, while the HD6870 has better tessellation support, else they are actually almost identical in most benchmarks.
OK so 6950/6970/6990 are VLIW4 and because of lower number of users they are not optimized like VLIW4 hardware which has so many users.
I will buy socketed Kabini (tomorow is an official launch of the AM1 platform) to see if that will be well optimized (and with hyperz please, that is badly needed there and every little optimization is counted). It is low end hardware but AMD sell many variants of it, so i guess numbers of users will be great there .
Also devs, Windows XP hits EOL today (just 12 hours remains to the end of XP era, one third of people using computers goes EOL today ), so please optimise kabinis to at least glamor to be snappy .
Heh there are first linux benchmark of AM1 on Linux . Athlon 5350, and seems like Athlon 5150 and Sempron 3850 will follow
And by the way, the latest AMD beta Catalyst drivers are awesome on Mint 16. On AMD A8 6600K, when I played HL2 earlier, then I was limited to 720p High without AA, not with the latest Beta, I can go full 1080p, very high with 8x Anti Aliasing without any input lag.
Trinity and Richland are actually VLIW4. Llano was VLIW5, if I remember correctly, while Kaveri/Kabini are GCN.
Originally Posted by Kivada
This reminds me: AMD, please send Vadim a Cayman-level card or APU. I think he still doesn't have one, and SB needs Cayman optimizations.