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

[J. Roeleveld]

On December 8, 2018 6:23:04 PM UTC, Dale <rdalek1967@×××××.com> wrote:
>Alexander Puchmayr wrote:
>> Am Donnerstag, 6. Dezember 2018, 10:27:31 CET schrieb Dale:
>>> Howdy,
>>>
>>> I mentioned in other threads that I'm doing some upgrades to my
>system.
>>> My first question is about a CPU upgrade.  I currently have this for
>my
>>> CPU, from cpuinfo:
>>>
>>> AMD Phenom(tm) II X4 955 Processor
>>>
>>> I've bought but not yet installed a FX-8350 CPU.  I have this in my
>>> make.conf file:
>>>
>>> CFLAGS="-march=native -O2 -pipe"
>> Compiling the whole system with -march=native might lead to troubles,
>
>> especially when doing a CPU change. This option means that gcc is
>determining
>> the type of CPU automatically and adjusts the instruction set used to
>exactly
>> this CPU. Although, in your case, it is highly likely that your new
>CPU
>> understands all commands from the old, but I wouldn't bet on it. Its
>possible
>> that your existing software encounters problems like "illegal
>instruction" or
>> the like. Very bad if your compiler crashes after CPU replacement,
>then you
>> cannot emerge anything. I highly recommend using CFLAGS="-O2 -pipe"
>and
>> nothing more, the performance difference is, if measurable at all,
>negligible.
>>
>>> USE_CPU="fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>cmov
>>> pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
>>> pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
>nonstop_tsc
>>> extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic
>>> cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt
>>> nodeid_msr hw_pstate npt lbrv svm_lock nrip_save"
>>>
>> As someone else in this thread already mentioned, USE_CPU is not
>used. What
>> you're looking for is CPU_FLAGS_X86=..., which defines what
>cpu-specific options
>> will be enabled for packages supporting it and where it makes sense.
>See
>> package cpuid2cpuflags for details.
>>
>> Regards
>> 	Alex
>>
>
>It seems the holiday shopping is slowing down delivery.  My fan was
>supposed to be here today but didn't arrive.  Since I got time, I'll
>change the CFLAGS for at least the @system stuff, that should get me
>booted for sure.  While the native setting makes things easier for
>normal use, I can see the point of not using it when changing CPUs. 
>That is one reason for this thread.  The CPUs are different and may
>require some changes during the swap. 
>
>Is there a easy way to see what if any changes will be made?  I did a
>emerge -UDNa @system but it's not showing any change.  Does it require
>a
>emerge -e @system to force the change?  Or is it not changing anything?
>
>Thanks much.  Better safe than sorry.  ;-)
>
>Dale
>
>:-)  :-) 

A CFLAGS change requires a rebuild of all packages done with gcc. I am not aware of a simple way of only doing those, so a "emerge --empty @world" will be needed.

--
Joost
-- 
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