Intel C2D COREs not used equally in FreeBSD 7.0-CURRENT i386

Doug Ambrisko ambrisko at
Wed Jun 6 16:41:48 UTC 2007

Dag-Erling Sm\xc3\xb8rgrav writes:
| Oliver Fromme <olli at> writes:
| > It's a common mistake to assume that amd64 only makes sense
| > if you have >= 4GB RAM.  There are several reasons why it
| > might be useful to switch from i386 to amd64:
| >
| >  - Most programs (though not all) will run faster, because
| >    in amd64 mode there are twice as many general-purpose
| >    registers, giving compilers much better opportunities
| >    for optimizations and caching of values, and reducing
| >    slow memory accesses.
| "twice as many" is an understatement.  AMD64 has 16 GPRs vs i386's 8 if
| you consider BP, SI, DI and SP as GPRs (as the AMD and Intel literature
| does); in practical terms the score is 12 to 4.
| >  - Some applications might benefit from a larger virtual
| >    address space > 4 GB.  (Note that this is not related
| >    to the amount of physical RAM!)
| For instance, Varnish maps its entire storage into memory, and will
| benefit greatly from the increased address space.
| > In practice there's (almost) only one reason not to run
| > FreeBSD/amd64 on amd64-capable hardware:  If you depend
| > on a certain piece of software which is known not to run
| > correctly in 64bit mode.  Fortunately those are not many.
| The only one I can think of (for a desktop) is the Flash plugin.

Why?  With the nspluginwrapper we can running Linux Flash in a FreeBSD
native browser on amd64 or i386.  With the appropriate compile foo
or probably by getting a Linux compiled version it would work with
a Linux browser.  Nspluginwrapper is great for running i386 plugins
on amd64!

The only thing that is preventing me from running full time on an
amd64 kernel is the kernel support for suspend & resume.  I had to
add a small hack the kernel to let the i386 Xserver to run on amd64.
I need to do some more digging to answer some questions that alc had.

Personally, I want to run amd64 full time so I can run and build amd64
and i386 things on my laptop without rebooting at native speed.

Doug A.

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