Re: [gentoo-user] Re: CPU upgrade and LVM questions.

[Dale]

Nikos Chantziaras wrote:
> On 06/12/2018 11:27, Dale wrote:
>>
>> I've bought but not yet installed a FX-8350 CPU.  I have this in my
>> make.conf file:
>>
>> CFLAGS="-march=native -O2 -pipe"
>> USE_CPU="
>
> USE_CPU does not do anything, AFAICT. CPU features are specified in
> CPU_FLAGS_X86. You can get appropriate flags using the
> app-portage/cpuid2cpuflags tool. For example, here:
>
> $ cpuid2cpuflags
> CPU_FLAGS_X86: aes avx mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1
> sse4_2 ssse3
>
> So in my make.conf, I use:
>
> CPU_FLAGS_X86="aes avx mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1
> sse4_2 ssse3"
>
>

I was wondering if those are used anymore.  I did that a looooong time
ago.  Things change.  After I do the swap, I'll get the settings up to
date.  No need changing things now just to change them again later. 
Besides, the current settings may be better when I install the new one. 
I did have the correct one in make.conf but didn't notice it to post.  I
did comment out the old unused one tho.  The current setting is this:

CPU_FLAGS_X86="3dnow 3dnowext mmx mmxext popcnt sse sse2 sse3 sse4a"

I'll update that when I get the new CPU installed.  I already have
cpuid2cpuflags installed.  At least now I know it is the current tool to
use.  ;-) 

I wish the monthly news letter would come back to let us know about some
of these changes.  Some things don't require a news item but we still
need to know when we can remove outdated stuff and add new stuff. 


 
>> Those were put there ages ago, likely when I built and installed Gentoo
>> on this rig.  Do I need to change those to something that is compatible
>> with both CPUs and then change to the new CPU after it is installed?  Or
>> will the new CPU be close enough that it won't matter?  Right now, I
>> don't know for sure what the new CPU supports or doesn't.
>
> Just install the new CPU and run cpuid2cpuflags to see what to put in
> CPU_FLAGS_X86. You can delete USE_CPU as that doesn't seem to be used
> for anything.
>
>

Old setting gone.

>
>> While at it, going from a 4 core CPU at 3.2GHz to a 8 core CPU at
>> 4.0/4.2GHz, just how much increase can I expect?  Will it double and
>> that's about it or will it be more than that?
>
> You won't get anything close to double the speed. The extra cores will
> mostly go unused, unless you use applications that make use of them.
>
> You will still get a speed up due to the newer CPU architecture and
> the higher frequency.
>
>

What I was thinking about is something like when compiling and all the
cores are used.  In other words, CPU is at max load.  Right now, I have
only 4 cores.  New CPU doubles that and each core is faster as well.  As
a example, Firefox takes about a hour to compile.  I was hopeful that
would drop to 30 or 35 minutes or so.  I realize there is some overhead
on this so it isn't a exact thing.  I was just curious about a rough
number to expect.  I know upgrading from 16GBs of ram to 32GBs has
helped.  I tested Dolphin the other day and it still have its memory hog
issue.  At least this time I had enough memory that it didn't cause a
crash.  ;-)


>> Also, since it has two
>> speeds, will it run at the slower or faster one?  Will it depend on
>> load?  I've never had a CPU with two clock speeds like this before.
>
> The two speeds specify the lower and upper speeds, depending on how
> many CPU cores are currently being under load, and also how much load
> there is. You don't have to worry about it though. It's all automatic.
> When you're not running anything that stressed the CPU, clock speeds
> are actually lower than 4GHz (some CPUs can clock down to 1GHz or so
> when they're idle and not doing anything.) Once something CPU-heavy
> runs, it will clock up to 4.2GHz. If you run something that stresses
> all CPU cores, then it will go to 4.0GHz to avoid overheating.
>
> But again, all this is automatic.
>
>
>


That's good to know.  That I was wondering about and couldn't find a
clear answer on.  I didn't know if I needed to install something to
manage that or what.   At least now I know to install the CPU and it
will do its own thing without me having to worry about it.  BTW, I know
my video card does that too.  The processor on it varies its clock speed
by a fairly wide margin.  Speaking of, I also found a MSI GeForce GTX
650 1GB Video Card.  It is a used card but it is faster I think than my
current 220 series.  Keep in mind, my idea of gaming is Kpatience.  The
biggest load is watching TV.  ;-)

Thanks for the info.  This answers a lot of questions I had.  Makes me
hopeful that this will work like I expect. 

Dale

:-)  :-)