Re: Guiding a 14 year old nephew on building his own computer

s wrote:
> On 8/29/2020 6:13 PM, bad sector wrote:
>> On 2020-08-29 19:28, s wrote:
>>> On 8/27/2020 7:13 AM, bad sector wrote:
>>>> On 2020-08-27 00:37, s wrote:
>>>>>
>>>>> My nephew is 14 and living in another state who wants to build his 
>>>>> own computer.
>>>>>
>>>>> I sent following YouTube videos for him to watch and learn how to 
>>>>> do it.
>>>>>
>>>>>
>>>>> Build a PC - Step-by-step
>>>>> https://www.youtube.com/watch?v=IhX0fOUYd8Q
>>>>>
>>>>> Beginners Guide - Build a PC
>>>>> https://www.youtube.com/watch?v=fVmcD8v3vR4
>>>>>
>>>>> How To Build a $500 Gaming PC
>>>>> https://www.youtube.com/watch?v=dFyhn6seoow
>>>>>
>>>>> The idea is to assemble a basic PC using which he can do homework, 
>>>>> learn new topics etc.
>>>>>
>>>>> Would the following parts be compatible to buy, assemble?
>>>>>
>>>>> https://www.amazon.com/Cooler-Master-Transparent-Adjustable-Ventilated/dp/B0785GRMPG/ 
>>>>
>>>>
>>>>
>>>> I like that case, made me one ten years ago that draws filtered air 
>>>> in via the raised bottom and 3 4" silent fans with all other fans 
>>>> reversed if required. Has been working very well with cpu never 
>>>> above 47c.  I have another idea now but before that I might just get 
>>>> me one of those cases from amazon!
>>>
>>> Would the single fan in this 
>>> https://www.amazon.com/Cooler-Master-Transparent-Adjustable-Ventilated/dp/B0785GRMPG/ 
>>> be enough for cooling?
>>
>> Cooling always depends on ambient conditions and cpu and cards and 
>> such. The fact that it's a best seller on amazon would I think speak 
>> well for it under average or better conditions, power supplies, CPU's, 
>> some video cards and drive racks have their own fans in addition. I 
>> would have no problem ordering it. For a beginner who isn't going to 
>> jump right into hacking and cannibalising hardware it's plenty good 
>> enough :)
>>
> 
> Thank you! I appreciate the prompt clarification.

You use the system cooling equation for that.

    By now, you might be saying, "how can I figure out what fan to
    use for the case ?". Well, there is an equation for that too.
    Now, for this one, you need to know all the thermal loads inside
    the computer case. We have the 125W processor, say a 100W
    video card, two 12W hard drives, say a total of 250W. Our definition
    of a well cooled case, is 7C, which is equal to 12.6 Fahrenheit degrees.
    Plugging in the values.

    CFM = 3.16 * Watts / Delta_T_degrees_F

    CFM = 3.16 * 250W / 12.6F = 62.7 cubic feet per minute.

It would take two rear fans of 35CFM each, to give 70CFM to cool
the air inside the case to "only" a 7C rise above ambient.

If room temp is 20C, then case air is 27C under those assumptions.

You're trying to keep the hard drive temperature below 60C,
if you need a metric. (The air can't be 60C! If the air was
40C, maybe the disk is 60C.) And you don't want the CPU getting
so hot, that it throttles because you didn't have a good
enough fan on the back. Using a utility like Speedfan (almico.com),
you can monitor various temperatures and see how close to an
ideal situation you're in.

For most people, a realistic value for system power is the
hard part. If the fan were to be "temperature controlled",
it could "rail" when the computer is gaming, and "loaf"
when the machine is idle. I like to run mine at a fixed
speed, so that if a fan is failing and slowing down, I
can notice the change with my ear. But others like
their temperature-controlled fans.

My newest machine is probably off the ideal value by
around half. So my case cooling is only about 50% of
what it should be. But the 110CFM fan that used to be
in the computer case, was causing "hearing loss", so
it had to go :-)

And I know what the power usage on the Test Machine is,
because it has a Kill-O-Watt meter connected. It draws
180W when all cores are loaded. If the video card cuts in,
it might hit 340W. If AVX is used, that's another increment.
I try not to run it too long with synthetic tests on
it (with the low capacity fan at least). I don't have
a problem running it all day at 180W though (compressing
an entire disk drive). I know the VCore regulator doesn't
have a big enough heatsink on it, which is the limitation
on my system (don't want to damage it). What's funny is,
the computer I'm typing on, has a metric acre of copper
to cool VCore, and it doesn't even get luke warm. The
computer where they knew the power would be 4X higher, they
put this shitty little cooler on it (probably just
aluminum too, not a copper one).

When buying the motherboard, I neglected to note just how
poor that cooler was. But I figured it out, the day I
"built up" the computer on the kitchen table, without fitting
it into the computer case. I run them first, without a computer
case, then I "run a finger over the hot stuff", just
to spot issues. And that's when I burned my finger on
VCore :-/ I had to fit a small fan, just for Vcore.

The clever guys at some of the review sites, they use a
FLIR infrared camera to spot build issues. Typically
the camera overlays a low-res infrared image on top
of a slight-higher res visible image, and from that,
you can spot issues with precision. For example, when
someone spotted an eight-pin DIP running at 100C, that
was dead easy with an IR camera. I would have missed
that, using my finger, as I would never suspect such
a small chip of running that hot. I'd hate for an
engineer to have done that on purpose.

    Paul