Re: [gentoo-user] Better CPU for compiling with gcc

[Alan McKinnon <alan.mckinnon@gmail.com>]

On 10/11/2015 20:37, Stanislav Nikolov wrote:
> 
> 
> On 11/10/2015 08:17 PM, Mick wrote:
>> On Tuesday 10 Nov 2015 17:47:08 Stanislav Nikolov wrote:
>>> Dear Gentoo users,
>>> I'm building a new PC. I have a budget of ~$550-$650. No GPU, no special
>>> case (I may use a card box), not even a hdd or ssd. So, as you can see,
>>> it's pretty much "get the best CPU and mobo/ram that are compatible with
>>> it". The problem is, which is the best one. By "best" I mean to compile
>>> shit fast. My laptop with 3rd gen i5 compiles firefox for 40 minutes on
>>> average.
>>>
>>> The most expensive Intel CPU is the skylake i7-6700k. But is it the best?
>>> Is there something from AMD that will perform even better? I can't find
>>> any benchmarks with AMD/Intel CPUs. And how much does the mobo matter?
>>> Will a cheap $30 400W PSU power that thing?
>>>
>>> Thanks
>> I don't (yet) own a i7-6700k, but my 6 year old laptop with (1st generation) 
>> i7 Q720  @1.60GHz takes slightly less than yours:
>>
>>      Sat Oct  3 14:35:40 2015 >>> www-client/firefox-38.3.0
>>        merge time: 36 minutes and 53 seconds.
>>
>>      Fri Nov  6 09:10:06 2015 >>> www-client/firefox-38.4.0
>>        merge time: 38 minutes and 8 seconds.
>>
>>
>> In contrast a year old AMD A10-7850K APU is significantly faster:
>>
>>      Sat Oct  3 19:40:48 2015 >>> www-client/firefox-38.3.0
>>        merge time: 17 minutes and 42 seconds.
>>
>>      Fri Nov  6 08:41:02 2015 >>> www-client/firefox-38.4.0
>>        merge time: 18 minutes and 18 seconds.
>>
>>
>> I would also be interested to see compile times of more modern i7s and FXs, 
>> but bear in mind that in single core operations Intel is these days 
>> significantly better than AMD.
>>
> So, I shouldn't prepare for a 8x times faster compile time... :(
> 



I can't help but think you are approaching this from the wrong perspective.

Why exactly are you using compile times as your sole criterion? Are you
building a compile farm for Ubuntu? Running continuous integration tests
for LibreOffice [on a $600 budget in a cardboard box :-) ]?

Or do you want emerge world to get it over with quicker?

If the latter, you better rethink your priorities. In computing terms,
compilation is a rare event; launching apps is a common event; and
writing to the disk happens all the time. Optimize for the common case.

A CPU never works in isolation, it is always part of a much larger
system, like disks, RAM and all possible kinds of I/O. The best CPU on
the market plugged into a POS motherboard will perform on emerge world
like a piece of shit - it will follow the weakest link.

If you want to build a compiling machine, buy the best collection of
stuff that works together well and still fits the budget. If you want a
machine that you can use and be happy with, ignoree the temptation to
must have the biggest baddest fastest CU (you will never get to use all
that big bad fast) and invest rather in gobs of RAM and an SSD. Remember
that apps are launched many times more than they are compiled. Or put
another way, sacrifice compilation times t get something you can use.



-- 
Alan McKinnon
alan.mckinnon@gmail.com