So ..
you are saying that SGI don't know what they are manufacturing and don't care that customers will notice that it's all snakeoil. Yeah, right.
The fact, by the way, that you can read (any) comments in the kernel source is a strength. Who knows what nightmare is in the Windows source.
From an Intel paper software.intel.com/sites/oss/pdfs/mclinux.pdf
2.6 Linux kernels (which have better SMP scalability compared to 2.4 kernels)
From a MIT paper pdos.csail.mit.edu/papers/linux:osdi10.pdf
"First we measure scalability of the MOSBENCH
applications on a recent Linux kernel (2.6.35-rc5, released
July 12, 2010) with 48 cores...."
"FreeBSD, Linux, and Solaris [54], and find that Linux
scales better on some microbenchmarks and Solaris scales
better on others. We ran some of the MOSBENCH appli-
cations on Solaris 10 on the 48-core machine used for
this paper. While the Solaris license prohibits us from re-
porting quantitative results, we observed similar or worse
scaling behavior compared to Linux; however, we don’t
know the causes or whether Solaris would perform better
on SPARC hardware. We hope, however, that this paper
helps others who might analyze Solaris."
From The Register http://www.theregister.co.uk/2010/11/10/redhat_rhel_6_launch/
On 64-bit x64 platforms, it can scale to 128 cores/threads and 2TB of main memory using one set of kernel extensions and to 4,096 cores/threads and 64TB of main memory. (Not that anyone can build a system with that many processors or that much memory yet.)
These are NOT clusters - I used a 1024 node cluster YEARS ago - these are for single image machines. I notice you've had the same arguments with different people all over the net. They all told you you were wrong.