This is true but it has been known that from time to time engineering samples will have serious faults.
There may be performance improvements with final software and production hardware but the important detail as far as it applies to the objection to Apple marketing up to 2x the CPU performance is that the new top-end 12-core will not be double the performance of the old top-end 12-core nor close to it.
Up to is awesome wiggle room. I don't expect every thing to be 2X faster, however anything leveraging new instructions has the possibility of being much faster. The problem is do bench marks this old really reflect what an unreleased processor can do?
That would require Intel's performance-per-watt to increase 4x in 2 architecture steps, which doesn't happen. There should have been 3 steps since the old Mac Pro but there weren't. It's fair for people to object to their marketing but marketing material is usually not that accurate and they typically detail the comparison they use in their marketing pages. They did the same thing last year:
It is only fair to object if the marketing is completely false. The reality is this isn't even the marketing of a released product.
"in other promotional copy, Apple did reveal that the fastest custom configuration "Mid-2012" Mac Pro -- the Mac Pro "Twelve Core" 3.06 (2012/Westmere) -- is between 1.2 and 1.5 times faster than the fastest custom configuration "Early 2009" Mac Pro -- the Mac Pro "Eight Core" 2.93 (2009/Nehalem).
First, it is worth noting that this official comparison is a synthetic performance test using the "STREAM" 5.8 benchmark, and is a comparison with the much earlier "Early 2009" line rather than the previous, and effectively identical, "Mid-2010" Mac Pro line."
I've been on the "when is a real MacPro update coming band wagon" for a few years now as I've seen nothing to indicate a real enhancement of the machine. I know that in part that is Intels fault. However in many ways this new Mac Pro does look like a solid update many have been waiting for. It isn't just faster processors but faster memory systems and greatly enhanced GPUs. I really see many tasks running much faster on this machine.
Some people will be disappointed they can't buy two 12-core processors but a Mac Pro like that would cost over $7500 so it affects very few people and Apple has never used the highest end processors in the past. What Apple would have used if they'd gone with two CPUs is a dual 8-core and it would have offered up to 50% more CPU performance for about $1300 more.
Most of these issues will be solved by a process shrink to 14nm or whatever feature size they hit. That could be as soon as 2014, though it might take another year for XEON to transition.
Beyond all of that the impact of cores starts to get real interesting past the 12 core level. Many apps that might be seen as embarrassing parallel end up not getting the performance increment expected due to bandwidth limitations outside the cores. I don't see a rush to many more cores in a workstation environment until this is dealt with. Fortunately the industry is trying to address this with faster RAM subsystems and other architectural improvements.
Of course XEON isn't a workstation only processor, so more cores can still be useful for server duties and the like. I just don't see the same advantage for workstations due to the highly varied workloads seen in the workstation market.
That extra performance option isn't essential because real-time feedback isn't required from CPU tasks. People who need more CPU performance can buy more machines e.g get a 6-core slave Mac Pro in addition to the 12-core. Less convenient in some cases but media software is using OpenCL more so the GPUs will provide good value there.
It is only convenient if the software you are using can leverage the hardware. Sometimes though ore machines actually makes lots of sense especially if bandwidth issues mentioned above raise their ugly heads.
I saw a chart somewhere, can't remember where that show the ultimate performance possible from these ne intel chips based on the number of cores implemented. Due to clock rate issues with the 12 cores, the ultimate computational potential verses the other chips wasn't all that great. Many people will be just as well off sometimes far better off going with a six core or other lesser implementation simply due to the ability to run at a far higher lock rate. If your software of choice is only lightly multi threaded it may be a mistake to even look at a twelve core model this year. Of course that is this year, one process shrink and a twelve core machine could become more mainstream.
One thing for sure, I see us at the same point the industry was in when dual core machines started to arrive for mass sale. Dual, even Quad core is mainstream now, we will quickly see six and eight core machines become the mainstream. I'm not sure if the iMac will get six cores this year but it is certainly a possibility but by 2014 I can see it as a requirement. Whatever issues the new Mac Pro will have with the 12 core won't last long at all. They really have no choice because six cores will soon be mainstream for desktop machines.