I am 'hopeful' for Vega, but almost think we will just get 2x Polaris for 2x the price. AMD hopefully has something up their sleeve....and they will need to be providing some solid performance leaks and (accurate) prerelease hype to keep people from still buying 1080s/1080Tis. I really wanted to go AMD this year, but nothing on the mid high-end to choose from. Hoping Vega is a home-run.
2X the performance of an RX 480 would put it faster than an AIB 1080 and all that for $499 vs. $650-700 that NV charges? That's how hype gets started without any basis for it. You made your prediction sound disappointing but to me that would be a huge win if true. It would essentially mean a card 25% faster than the reference GTX1070 for only $50 more or similar performance to the GTX1080 for $150-200 less. I doubt Vega 10 will be that competitive. AMD is going to need to fill in $329-499 price levels with cards between RX 480 and the GTX1080. This is why AMD already confirmed they will have Vega 10 and Vega 11. The confusing part about these 2 chips is that AMD has Vega with HBM2 on the roadmap, which doesn't align well with some speculation that Vega 10 may be GDDR5X and Vega 11 (larger chip) would be HBM2.
What could AMD possibly do to increase throughput of their GPUs? Next gen. rasterization? Next gen. schedulers?
Is there anything that would make 4096 GCN core, and 1TB/s of bandwidth fully utilized?
I know I may sound a little excited on this topic, but I want to know what might appear in next gen. Mac Pro .
At the same GPU clocks and on paper memory bandwidth,
Polaris 10 (4th gen) is just 18% faster on average against Tahiti (7970) but is only 7% faster against Tonga (R9 380X). That means in nearly 5 years AMD has improved IPC by just about half of what NV did in 2 years moving from Kepler to Maxwell (35-40%). Given AMD's current track record in improving IPC for GCN over 5 years, I would not expect any major improvements in architecture with Vega (0-10%). Chances are AMD will use the wide core approach (close to double everything) because it's unlikely they will use the brute force (GPU clock speeds) approach of their competitor. Most 'reasonable' estimates for Vega 10 are 4096 SPs, 256 TMUs, 64 ROPs, HBM2.
Computerbase shows only a 4.3% advantage for 2304 SP RX 480 against 2048 SP RX 480 at the same GPU/memory clocks. This suggests a severe memory bandwidth or some other bottleneck (ROP?). Despite 12.5% higher shaders and textures, the RX 480 is unable to translate this on paper advantage to real world games. This means AMD is going to need the fastest GDDR5X they can get their hands on or have no choice but to wait for HBM2. In order to improve perf/watt, as their road-map suggests, they are going for HBM2 for maximum efficiency. This is where things get tricky for AMD. SK-Hynix shows only 2 options on their road-map for Q3' 2016:
H5VR32ESM4H-12C 4GB 4Hi = 204GB/sec 1.6Gbps
H5VR32ESM4H-20C 4GB 4Hi = 256GB/sec 2.0Gbps
If they choose the former, they will likely need 4x4Hi = 16GB 800GB/sec. 16GB seems massive overkill for this generation of gaming. You end up with wasted VRAM, higher cost, higher power usage.
If they choose the latter, I am not sure you can do 2x4Hi = 8GB 512GB/sec. 8GB is a good spot to be in but 512GB/sec memory bandwidth seems borderline low for a 4096 SP, 64 ROP GCN 4.0 because RX 480 is already memory bandwidth bottlenecked with 256GB/sec.
Here is another issue: if Vega 10 is only 4096 SP, 64 ROP, 256 TMU, 512GB/sec 250W TPD design, if linear scaling was 2X over RX 470,
the card would only end up slightly beating the GTX1070. Since Polaris 10 is only a 5.7B chip, the Vega 10 with these specs would fit at ~ 11B, but the rumours have been whispering that flagship Vega would be ~ 15-18B transistors. Not adding up.
On the surface it seems we could see a 3500-4000 Vega 10 with 10-11B transistors but they could also be a much larger 5000-6000 shader Vega 11 with 15-18B (or the rumours are just that - unsubstantiated dreams). What makes it so difficult to estimate is AMD's vagueness and the gargantuan gap that exists in performance between the RX 480 and GTX1080/Titan XP. It doesn't seem realistic for a 1.2-1.3Ghz Vega 10 to be both a competitor to GP104 and GP102.
IMHO, AMD's best bet to improve performance will be going wider (more functional units), and maximizing perf/watt at the transistor level just like NV mentioned they spent months trying to maximizing clock speeds on 16nm node. AMD's Polaris 10 clocks were a disappointment for a 14nm node. Whatever I typed is pretty much nothing new though.