# What causes "SMP"

## miqorz

Okay Im baffled here..

This is my uname -a...

```

Linux melvin 2.4.25 #7 SMP Tue Apr 6 22:02:48 EDT 2004 i686 AMD Athlon(tm) XP 2000+ AuthenticAMD GNU/Linux

```

I don't remember checking in SMP support anywhere and I cant figure it out..

Anyone know what could be causing this? Im using a vanilla kernel and not genkernel.

And I dont have an SMP system.. any ideas please?

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## steel300

Under Processor Types and Features in menuconfig, there's an option for Symmetric  Multi Processing (SMP), that is checked. If it wasn't, than it wouldn't display SMP in uname.

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## ewan.paton

usually smp is enabled by checking Symmetric multi-processing support box in the Processor type and features section

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## miqorz

/usr/src/linux-2.4.25/include/linux/kernel_stat.h: In function `kstat_irqs':

/usr/src/linux-2.4.25/include/linux/kernel_stat.h:62: error: `smp_num_cpus' undeclared (first use in this function)

/usr/src/linux-2.4.25/include/linux/kernel_stat.h:62: error: (Each undeclared identifier is reported only once

/usr/src/linux-2.4.25/include/linux/kernel_stat.h:62: error: for each function it appears in.)

In file included from /usr/src/linux-2.4.25/include/linux/interrupt.h:52,

                 from ksyms.c:21:

/usr/src/linux-2.4.25/include/asm/hardirq.h:37:1: warning: "synchronize_irq" redefined

In file included from /usr/src/linux-2.4.25/include/linux/modversions.h:135,

                 from /usr/src/linux-2.4.25/include/linux/module.h:21,

                 from ksyms.c:14:

/usr/src/linux-2.4.25/include/linux/modules/i386_ksyms.ver:92:1: warning: this is the location of the previous definition

make[2]: *** [ksyms.o] Error 1

make[2]: Leaving directory `/usr/src/linux-2.4.25/kernel'

make[1]: *** [first_rule] Error 2

make[1]: Leaving directory `/usr/src/linux-2.4.25/kernel'

make: *** [_dir_kernel] Error 2

root@melvin linux #

I get that when I try to compile without SMP with a vanilla kernel.. what's up with that?

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## slycordinator

You probably have something else in your kernel that requires SMP.

Also if you have a processor that supports stuff like multi-threading (pentium 4 or athlon xp's for instance) you'd want SMP.  Otherwise, the multi-threading would never be used.

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## miqorz

I have an AMD Athlon XP 2000+ ; so its best off I leave SMP enabled?

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## steel300

 *miqorz wrote:*   

> I have an AMD Athlon XP 2000+ ; so its best off I leave SMP enabled?

 

If it won't compile, then I'd leave SMP enabled. It's not hurting anything, it's just a cosmetic issue. Possibly make clean, then make dep && make clean bzImage modules modules_install would fix it.

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## ewan.paton

 *slycordinator wrote:*   

> You probably have something else in your kernel that requires SMP.
> 
> Also if you have a processor that supports stuff like multi-threading (pentium 4 or athlon xp's for instance) you'd want SMP.  Otherwise, the multi-threading would never be used.

 

no amd chip suports hyperthreading nor are they likely to in the future due to the nature of their design, guess all the smt engineers working at alpha went to intell

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## slycordinator

 *ewan.paton wrote:*   

> 
> 
> no amd chip suports hyperthreading nor are they likely to in the future due to the nature of their design, guess all the smt engineers working at alpha went to intell

 

Guess all the "smt" engineers at "intell" were shocked to see that the amd chips do nearly as well as their chips with a) a much lower bus speed, b) quite slower bus speed, and c) no hyperthreading.

Just goes to show you that good design can overcome speed.

btw: AMD has a patent that could easily lead to similar hyper-threading technology. http://www.theinquirer.net/?article=6773

And according to AMD's benchmarks (which have to be taken with a grain of salt) P4s do better with hyperthreading turned off.  http://www.amdmb.com/news-display.php?NewsID=6479

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## ewan.paton

 *slycordinator wrote:*   

>  *ewan.paton wrote:*   
> 
> no amd chip suports hyperthreading nor are they likely to in the future due to the nature of their design, guess all the smt engineers working at alpha went to intell 
> 
> Guess all the "smt" engineers at "intell" were shocked to see that the amd chips do nearly as well as their chips with a) a much lower bus speed, b) quite slower bus speed, and c) no hyperthreading.
> ...

 

yep i spell terible but symetic multi threading (hyperthreading for those who think chips should sound like startrek) or smt was corect. 

as to amd having a patent, big deal they already have access to all intel ip through some deal in the 80s if i recall, brittish rail had patents on space ships at one point.

the problem with the amd64 is it was never designed with smt in mind and retro fitting would be very dificult not to mention pointless as duel cores are only about a year away and its dubious if people need more than one processor these days anyway, proceesing 4 symultanious threads is a bit unnecisary that said i have a rig that can so cant complain to much

oh and i wasnt trying to attack your post but points like that can be read by folks and when the get their amdxp wonder why they cant get HT to work, perhaps i should have been a bit more polite but its early in the morning here and think their is something seriously wrong (like expensive) with my hardware

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## shanenin

I remeber when I was building LFS if SMP was enabled in the kernel, I could not get my network online. By chance I diabled it and my network started working. Now the first thing I do with make menuconfig is disable SMP

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## slycordinator

 *ewan.paton wrote:*   

> 
> 
> yep i spell terible but symetic multi threading (hyperthreading for those who think chips should sound like startrek) or smt was corect. 
> 
> as to amd having a patent, big deal they already have access to all intel ip through some deal in the 80s if i recall, brittish rail had patents on space ships at one point.
> ...

 

Point taken.

It just seemed like you were saying "Intel designers are smart and AMD designers are dumb."

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## ian!

Moved from 'OTG' to 'Kernel & Hardware'.

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## ewan.paton

nice idea changing the forum name as the kernel is most directly connected to hardware rather than posts all over the place.

as for intel being smarter than amd well if anything it apeares the other way round but only because management/marketing have been dicking about and the engineers have been shafted, pentium m wasnt under so much consumer preasure so while management wanted everyone to pay thousands for epic processors to go 64bit and trying to avoid using low k they got on with it and built a good chip.

you do have some sympathy for managment as intel is more profitable than ever, its the old paradime of quality vs proitabilty, if engineers are left to their own devices the build fantastic stuff like the VW beetle but in business terms it was a bad design as it was too good.

in engineering terms intel should mass produce the itanics at say £200 a throw{1} and kill the opteron in the server market not to mention ensure much greater software suport and economies of scale but then ibm would go to war on the desktop and they would lose the high premiums

there are numerous instances where good engineering is sacrificed for good business

{1} i know they say this will happen by 2007 but by then odds are it will be dead

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