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SubjectRe: Linux-2.0.11
RHS Linux User writes:
> i know this is prbably a silly question yet..... if i dont ask,, i wont
> get an answer therefore i wont know......
> i have a Intel 6x86 P120Mhz CPU and 64 bit mother board, pci based made by
> amptron.... is there going to be a 64-bit clean version for these 64 bit
> systems that will recognize the fact that they are compiling for ie a 686
> class 64 bit system..... and such......? I did notice that when trying to
> compile as a 586, on my AMD 5x86 133Mhz it only recognized the chip as a
> 486. are we over looking the 5x and 6x non-intel platforms..... or am i
> just clueless....?

First: dont bug Linus Torvalds with what you think is a silly
question (and yes, it is :)

Anyway, since the i386, the instruction set has only been very
slightly augmented on each new ix86 (only some stuff to make SMP
boards without too much pain on 586). The number of register has growed,
thats the reason of the -m486 flag of gcc. There is then no obvious
reason to make specific extensions of gcc on each stepping of brand
new intel, AMD, Cyrix or whatever.

The reason why the kernel config ask you about your CPU is to try to
turn on the best optimization for your CPU, but in no way gcc (at time
of this writing) will generate code only for P6 or AMD kX.
You can play with -malign-jumps=2 -malign-loops=2 -malign-functions=2
which align jumps/loops/functions on 64bits boundaries, the
performance improvement is most of the time psychologic :*)

There is a special gcc maintained by independent not involved with the
FSF which include some enhancements for P5 (pentium). I play with it once
myself(gcc 2.6.3p), and get back to the normal gcc since it doesnt
improve the speed of floating points intensive apps. (i'm playing with Fast
Fourier Transforms). If you are intersted by this gcc, look for
GCC+pentium on altavista.

And, at last, sorry but there is no 64 bits CPU with i386 instructions
set available at this time. intel P7 will be 64 bits, P6 is 32bits
with 64bits data path for increasing bandwith to the memory, but its
32 bits in addressing and all the rest (except for bus between
different logical unit inside the chip, once again to increase

Philippe Strauss, CH-1092 Belmont

******* Caution! don't use reply without changing "root" to "philippe.strauss"
******* in my email addr. (sendmail userdb not yet well configured ;*)

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