^^The trouble is that they would have run out of room.
There are a few issues we are not looking at.
1. Most games where the huge leads are shown are tested at 1024x or 1680x. You can't really be a serious gamer if you play at that resolution, can you? At higher (and more realistic) resolutions the CPU impact is far lower and apart from a few games the gap between CPUs is pretty much non-existent - even the Phenom 980 performs the same as the 2600k at 2560x in Metro2033, for example, let alone the FX. Those scenarios are more GPU-imited, and are more appropriate for gamers. At 1920x, a 8150 performs identically to a 2600k in Crysis 2 as per the Guru3D review. I don't see any reason for it being inferior, but maybe it's just me. Or maybe I'm blind and am the only one who can't make out a difference between 100 and 200fps, given my monitor only goes to 60Hz refresh anyway. I congratulate those of you on this thread who play games at 1024x and your 'superior' experience with better CPUs
2. The target CPU speed for the FX range was supposed to be 30% over Thuban. They didn't manage to hit it because of foundry issues (presumably). Obviously that aggressively impacted their performance in single thread and lightly threaded apps. In heavily threaded apps wth lots of FP load, the FX does compete equally with the 2600k. Had they hit the target clockspeed, things would have looked different.
3. If they had added two cores to the 1100T the motherboard would have blown some power circuitry even if rated to 140W. Clearly the approach required was different. Lengthen the pipe and pump up the clock. [Incorrect information mentioned here earlier, now edited]
4. For those about to buy, my observation is that if you are throwing random loads at the PC, a SB is the way to go. If you are a gamer with a proper monitor, you can get by with a Phenom 980x or pretty much anything with a decent clockspeed about 3GHz, architecture and vendor matter little. The only valid application of BD is in a fully professional content creation environment with a lot of heavily threaded workload, where the BD competes with the 2600k at a lower price.
5. One of the biggest issues that all the review sites do uncover is how badly Win 7 handles BD. Two INT cores is not easily understood by the OS, and this may lead to a huge performance hit. HT on the other hand is coded into the OS so Win 7 knows when the physical core is handling a thread and when the scheduler has taken over. In dev builds of 8 (which are coded correctly for BD) you can see increases of up to 15% already on existing benchmarks. Maybe just about enough to compete with the 2500k. Unfortunately when 8 is out the 2500k will have been retired. Wherever AMD is at that point in time, we'll have to evaluate given the existing situation.
6. I have two big disappointments. One is the huge hit on IPC over the previous generation of chips. This is not a new thing. Intel went through it twice, and more recently AMD suffered when it moved from VLIW5 to VLIW4 in their transition from 58xx to 68xx cards, which they could overcome only by adding more resources on the card itself. BD has done pretty much the same thing. The second disappointment is the power consumption, which I am hoping is a stepping issue and will be somewhat addressed in the shipping product because it's hitting the BD harder than the absolute performance.
All in all yes, a pretty disappointing release from AMD. I think someone dropped the ball very badly on this and all they can do to fix it is starve the supply and work quickly on the next versions of the chip.
This is a difficult choice to make in my situation (. Clearly the older Thubans deliver equivalent high-resolution gaming performance to Sandy Bridge, and since I don't use any professional apps at all it's tempting to not upgrade at all (or only a better CPU than my aging x2 550) till IB releases and/or AMD saves (?) their business.
@asingh, you do get CPU drivers. One example is the DC optimiser that was required around the time the Athlon dual-core series launched, as apps did not know how to use the second core even if the OS did.