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Intel's 3rd generation Core i7 Quad-Core processor (available 2012), is
the evolution of the i7 Quad introduced in 2009, and the only true quad-core
CPU to be available in laptops and notebooks. Of course, Linux has had support
for Symmetric Multi Processing (SMP) for many years, and this is quite mature,
so it comes as no surprise that Linux takes full advantage of these new CPUs
in portables.
The EmperorLinux Rhino M6700 is our fastest Core i7 system.
What can you expect from the Core i7 Quad CPU? Well, first off you have four
(4) processor cores, each of which is hyperthreaded, meaning you have eight (8)
execution cores. Meaning that in Linux you'll see 8 CPUs in /proc/cpuinfo, in
htop, and any other similar tool. In everyday applications, like email
(evolution, etc.), web browsing (firefox) and word processing (Open Office),
which are not "threaded" applications, you will not see much difference at all,
as they run on a single CPU core. Except that up to eight of these
single-threaded applications can run simultaneously at the full clock speed of
the CPU, and without having to contend with other processes for time on the
CPU. This lowered contention from that typically seen on dual core machines is
the win here.
If you are compiling code with well-written makefiles (like the Linux kernel
itself, which accept make -j N), run scientific applications, or have
any other software designed specifically to take advantage of SMP, you will see
the most improvements. We have seen kernel compiles completed in significantly
less than 1/3 the time (of a dual-core machine) when doing make -j 8.
You may have noticed that, while previous generation CPUs like the Core 2 Duo
T9900 were clocked up to 3.06GHz, the Core i7 Quad CPUs clock in at 2.2GHz to
2.5GHz. This is where Intel's Turbo Boost comes in. The rated clock speed for
an i7 CPU is the continuous duty clock speed if all 4 CPU cores are kept
maximally busy (as in a big render, kernel compile, or transcoding).
If any one CPU core does not have any work to do, then it can be turned off,
and the remaining cores can speed up (to take advantage
of the excess available thermal dissipation). Idling 2 cores lets the remaining
two go even faster, and by extension, when idling 3 cores, the one remaning core
will run very fast. The following chart shows the Core i7 CPUs,
and their turbo boost speeds based on the number of active cores. Clearly, you
can still have your 3.06GHz, and even go to 3.5GHz:
| Core i7-720QM |
1.6 GHz |
1.73 GHz |
1.73 GHz |
2.4 GHz |
2.8 GHz |
| Core i7-820QM |
1.73 GHz |
2.0 GHz |
2.0 GHz |
2.8 GHz |
3.06 GHz |
| Core i7-920XM |
2.0 GHz |
2.26 GHz |
2.26 GHz |
3.06 GHz |
3.2 GHz |
| Core i7-2720QM |
2.2 GHz |
3.0 GHz |
3.1 GHz |
3.2 GHz |
3.3 GHz |
| Core i7-2820QM |
2.3 GHz |
3.1 GHz |
3.2 GHz |
3.3 GHz |
3.4 GHz |
| Core i7-2920XM |
2.5 GHz |
3.2 GHz |
3.3 GHz |
3.4 GHz |
3.5 GHz |
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