Thanks for this helpful answer. I suspect it has to do more with the kernel or settings than the board itself as Windows7 works fine with all the cores, though I cannot load my XP onto it. I could only install XP in a virtualbox in Ubuntu.
I have actually tried FC11, but the live CD doesn't boot up with all cores enabled in BIOS. Also could not get the network up with just one core on, unlike Ubuntu 9.10. On searching the web I found there is something more to be done, but not conclusively, to make it work in FC11 for the e1000e driver, so I abandoned it temporarily and I thought I would wait for FC12 (due on 17th).
What did you do to get the network come up in FC11 and did you do anything specific in BIOS for it to work with all the cores? By the way, Phoronix's review of this board with Ubuntu 9.10 shows all the cores working that too with a pre-production board and BIOS, so it is just my frustration about what I am really missing.
I left the bios at its default settings and used the x86_64 network install cd rather than the live cd and kept getting a message about the lack of a network adapter. I ended up disabling the onboard LAN and installing an old PCI network card as a test. It worked and i`m just going to wait for the intel driver to make it into the kernel then take the card out.
I have got Fedora 12 x86-64 DVD and tested the media and found to be good. However, I still face the same problem - can't boot with all cores enabled in the BIOS. Surprisingly, while trying this DVD, the system booted once with Fedora and once with Ubuntu with all cores enabled. I didn't install Fedora and aborted it. In Ubuntu 9.10, I could see all the four cores listed in /proc/cpuinfo as well as system performance view as well. However, that was only "once" so far - a successful boot in about a month. This is really strange. Reverting to just one core - everything works fine and Windows 7 boots with all 4 cores enable all the time consistently. Here are the boot time messages. They are the same for Ubuntu 9.10 in recovery mode and with Fedora 12 DVD (except that I can't see the first two lines while booting Fedora ).
Initializing cgroup subsys net_cls
CPU: Physical Processor ID: 0
CPU: Processor Core ID: 0
CPU: L1 I cache: 32K, L1 D cache: 32K
CPU: L2 cache: 256K
CPU: L3 cache: 8192K
CPU 0/0x0 -> Node 0
mce: CPU supports 9 MCE banks
CPU0: Thermal monitoring enabled (TM1)
CPU 0 MCA banks CMCI:2 CMCI:3 CMCI:5 CMCI:6 CMCI:8
using mwait in idle threads.
Performance Counters: Nehalem/Corei7 events, Intel PMU driver.
...bit width: 48
...generic counters: 4
...value mask: 0000ffffffffffff
...max period: 000000007fffffff
...fixed-purpose counters: 3
...counter mask: 000000070000000f
ACPI: Core revision 20090521
ftrace: converting mcount calls to 0f 1f 44 00 00
ftrace: allocating 20852 entries in 82 pages
Setting APIC routing to flat
..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
CPU0: Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz stepping 05
Booting processor 1 APIC 0x2 ip 0x6000
At last the problem seems to have been solved. This was caused by - guess what - the good old rodent, my old mouse. While I got everything new, including the keyboard, for some reason I just connected my old mouse to the system and that seems to be causing all this problem. I plugged in a new mouse and bingo, everytime Ubuntu 9.10 also boots with all the cores enabled. Just to confirm I have disabled USB legacy support in BIOS and that also seems to solve the problem i.e. Ubuntu 9.10 boots with all the cores enabled, but with only one hitch - my keyboard is not enabled (though new) till the OS is loaded i.e. I can't use it in the grub menu.
So I am happy that the problem is solved by having a new mouse (Microsoft) and USB legacy support enabled (default option) in BIOS. BTW, Windows 7 boots fine any way. Let me test this in the days to come and confirm FC12 as well. Hope this helps.