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

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

On 10/11/2015 21:07, Stanislav Nikolov wrote:
> 
> 
> On 11/10/2015 08:55 PM, Alan McKinnon wrote:
>> 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.
> 
> 8GB of RAM are waaay more than I use daily (several firefox tabs, nvim = 2Gb max), I have a pretty fast SSD too. Even buying 8GB RAM and a brand new SSD, I have > $450 left. Can I buy a AMD CPU that will get the job done faster than 6700k and/or cheaper?
> 


That changes things. It wasn't obvious you already had RAM & SSD & stuff.

I'd first make sure I have a decent PSU - none of that crap puny
el-cheapo $300 shit (search list archives for 1000s of posts about dodgy
PSUs). Then split the difference between 8G RAM, a good CPU and an
excellent motherboard. You will use that extra RAM, and a motherboard
that ties all the bits together properly is much more cost-effective
than raw CPU grunt alone.

-- 
Alan McKinnon
alan.mckinnon@gmail.com