Why does FBSD always assume it's on an 8080 CPU?
John Merryweather Cooper
john_m_cooper at yahoo.com
Sat Jan 27 03:01:43 UTC 2007
Chris H. wrote:
> ...or when will FreeBSD support Pentium features?
> I want to apologize in advance if this should be on the kern@
> But it seemed apropriate for this list too and I'm already on it.
> I've noticed building kernels, that since v. >= 5 that during
> the phase 2/3 all the lines echoed to the screen contain:
> -mno-mmx -mno-3dnow -mno-sse -mno-sse2 ...
> As Pentium have been the "norm" for many years now, why aren't
> these /assumed/? I'm building on several SMP PIII's and a build
> is in process now on a PIV Athalon running 6.2 the source and
> ports tree were cvsupped 01-25 @02:03:00 -0800. Yet this
> current kernel build is echoing these same -mno- lines. I have
> machine i386
> cpu I686_CPU
> device apic
> uncommented and I386_CPU, I486_CPU & I586_CPU commented. I have
> grepped the /src/sys/conf/NOTES as well as the /src/sys/i386/conf/NOTES
> Yet the only case I find relating to this is on line: 130 in:
> /src/sys/i386/conf/NOTES which reads:
> # CPU_ENABLE_SSE enables SSE/MMX2 instructions support. This is default
> # on I686_CPU and above.
> Default? hmmm... not as far as I can tell. Anyway, I would *greatly*
> appreciate any insight on this issue. Do I need to pollute my make.conf
> file to achive a Pentium kernel?
> Thank you very much for all your time and consideration.
We already preserve the "core" CPU state and the FPU state between
context switches. Adding MMX into the mix means preserving an MMX state
(since it can clobber the FPU state) and so forth.
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