Oops, wrong cpu type in my kernel. Should I worry?

kakakoka

I forgot (somehow) to set the cpu type in my .config when I compiled my kernel a few days ago. It was wrongly set to 386, that should have been athlon. Im going to make a new kernel, hopefully with nothing about to break. Can this have any impact on the apps Ive compiled so far?

Also I hope it will make my desktop more responsive during this emerge openoffice I have going on, but which Im going to CTRL-C soon. Or will the change have no effect on desktop responsiveness?
_________________
Aspiring to once become a great geek
---
"Tachikoma": AMD TB 1300 Mhz, ECS-K7S5A (SIS 735), (noname) RADEON 8500, Hercules Gametheater XP, Pinnacle PCTV pro
"Pyonpyon": Athlon 2500+ Barton, MSI K7N2-delta-ISLR (Nforce2), Sapphire Radeon 9600 Pro

barlad · l33t Joined: 22 Feb 2003 Posts: 673

I don't think it will have any impact on the apps you have compiled. The apps you compiled depend on the CFLAGS and CHOST you set up in make.conf. If those are correct, then your applications are fine.

You can safely recompile your kernel with new CPU. Going from 386 to Athlon should definitely improve responsiveness without breaking anything (assuming you compiled your apps with proper flags).

Now I wonder if a kernel compiled with, let's say i386, could run some apps optimized for athlon (compiled with -march athlon). That would be fun to try.

Voltago · Posted: Fri May 21, 2004 4:53 pm Post subject:

Since the athlon is backwards compatible to its ancestor architecture i386, this will _not_ cause problems like stuff crashing. But there will be a slight performance loss due to missing athlon specific optimisations in your kernel.
It will, however, have not too big an impact on compiling stuff, I think, and you should complete your emerge before baking a new kernel. The time advantage when compiling openoffice with an optimised kernel will most likely not be worth the time already lost in your running compile.

kakakoka · Posted: Fri May 21, 2004 5:04 pm Post subject:

Im letting the emerge openoffice run

Basically I have been running for a few days with the 386 kernel and i686 flags in make.conf. The desktop does become quite unresponsive when emerging, so Im hoping my new kernel, which is configured but not compiled yet, will have a positive impact here

_________________
Aspiring to once become a great geek
---
"Tachikoma": AMD TB 1300 Mhz, ECS-K7S5A (SIS 735), (noname) RADEON 8500, Hercules Gametheater XP, Pinnacle PCTV pro
"Pyonpyon": Athlon 2500+ Barton, MSI K7N2-delta-ISLR (Nforce2), Sapphire Radeon 9600 Pro

kakakoka · Posted: Fri May 21, 2004 5:07 pm Post subject:

barlad · l33t Joined: 22 Feb 2003 Posts: 673

athlon setting is correct

Well, what I wonder is this:
When you run a program, I suppose that what happens first is that the kernel puts the assembly instructions in memory. Thing is the program contains some athlon's specific instructions and the kernel was compiled with i386 support. So I wonder if the kernel does any check on the instructions it's putting in memory or if it just loads it and let the CPU manage the rest.

I wish some system guru would just come and tell me how all of that works

Anyway, I guess that since you have not noticed any application not working properly, I have the answer to my question!

kakakoka · Posted: Fri May 21, 2004 9:50 pm Post subject:

None so far, although there have been one dmesg message im not sure how to interpret, I think its connected to fglrx (ati-drivers):

mtrr: no MTRR for c0000000,400000 found
mtrr: no MTRR for c0400000,100000 found

Im not sure what the MTRR does (except its a Memory Type Ranged Register), but I do have it compiled in and I do remember it to be next to the processor type selection in make menuconfig, so perhaps its related?

Oh, and by the way, the openoffice build finally failed after 5 hours of compilation. Oh well reaching for the -bin ebuild, that will do I think.

Halcy0n · Posted: Fri May 21, 2004 10:57 pm Post subject:

As far as I can tell (and am aware), all the processor type setting does is determine what flags to compile the kernel with. So you really have nothing to worry about, so long as you picked something compatible, which i386 would be.
_________________
Mark Loeser
http://www.halcy0n.com

jcmorris · Apprentice Joined: 11 Jun 2003 Posts: 174

Well, if you had an Athlon-XP, and you compiled your apps with -msse or -march=athlon-xp, there could've been problems, since SSE requires that the kernel initialize it and detect it on your processor. In other words, setting it to 386 would cause problems because the kernel wouldn't even check for SSE because you can't enable SSE on a 386. But, if you didn't compile your apps with SSE support, you are fine

jcm
_________________
Desktop:
Athlon64 3000+ (Socket 939 Venice)
Asus A8N-SLI
1GB Dual-Channel DDR 3200
NVidia Geforce 6800 256MB

Laptop:
IBM R40
Pentium M 1.4 GHz
256 MB RAM

herbo · Posted: Sat May 22, 2004 4:50 am Post subject:

The mttr is most definately connected to the fglrx (ati drivers), more information refer to the following link: mtrr fix @ rage3d forums

btw: I have the same message in my log, but it does not appear to cause any problems.

kakakoka · Posted: Sat May 22, 2004 7:58 am Post subject:

FYI. The mtrr message dissapeared on the correctly built athlon kernel.
_________________
Aspiring to once become a great geek
---
"Tachikoma": AMD TB 1300 Mhz, ECS-K7S5A (SIS 735), (noname) RADEON 8500, Hercules Gametheater XP, Pinnacle PCTV pro
"Pyonpyon": Athlon 2500+ Barton, MSI K7N2-delta-ISLR (Nforce2), Sapphire Radeon 9600 Pro

herbo · Posted: Sat May 22, 2004 1:26 pm Post subject:

Thanks for info, however the mttr message comes and goes me for.... not quite sure what causes it, but I think it might vmware or some other graphical ly intensive program. Ah well, I live in hope ATI will someday produce decent drivers to fix all these problems up.....