this heatsink right here pointless
four RAM slots you only need two of them and why is
there a pci express slot that has sli no
one uses it why the heck does everybody want all of this
it's because nobody actually knows what motherboards are and how they work so
here it is to the best of our ability how motherboards work so
buckle up nerds land is on vacation and we're not holding back just like i can't
hold back this segway to our sponsor i fix it you'd like to repair your own
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of this video
computer power supplies output 12 volts
if you apply 12 volts to a CPU it'll look something like this
hmm sub-optimal for sure
sub-optimal for sure to avoid the magic smoke we need to take
that 12 volts and step it down to something more like 1.2 volts and this
is exactly the job of voltage regulation modules the vrms that overclockers talk
about so much the basic circuit consists of two
mosfets which in this situation are basically just fancy switches
an inductor and a diode this first switch closes
which then charges this inductor converting the electricity into a
magnetic field the voltage the CPU gets
depends on how long this switch is closed but the instant it is opened the
voltage to the CPU begins to drop kind of like a
drain so this is where that diode here is very
important if both switches are open while the inductor is charged its
magnetic field will collapse and pop goes your CPU
but the diode is highly inefficient so it's important to get the second switch
closed as soon as possible to avoid creating any unnecessary heat if you're
paying attention you might have noticed a problem here though although the
voltage will be bouncing around what the CPU is asking for there are a lot of
spikes not great for stability and there are two ways to remove this the first is
to just increase how fast the mosfet switches on motherboards this is
normally done at about 300 000 times per second but even then the voltage can
fluctuate more than the CPU wants and it isn't practical to try switching a whole
lot faster than that every single time the mosfet switches on or off it
generates a bit of heat and above about 150 degrees celsius the mosfet's gonna
die so if we want cleaner power we don't
need faster mosfets we need more of them
the circuit we have here represents a single phase another term that
overclockers love to use so much so by adding another phase we can
roughly double how clean our power is with the benefits of additional phases
scaling roughly linearly from there the number of phases in your motherboard
is normally shown as a number like eight plus two which means eight phases for
the CPU and two dedicated for the RAM let me put this away
multiple phases also have another benefit say your CPU requires 100 amps
to run with a single phase all 100 amps would have to go directly through those
components but with two phases only 50 amps will go through each phase meaning
lower rated and thus cheaper components can be used
you might be tempted to think then well more phases equals more better
which is true to a point however as you add more phases controlling them can get
more difficult which translates into the vr as being less able to respond to
changes in voltage like everything then there are trade-offs between having less phases
with higher quality components or more phases with lower quality components
this does create a rather odd situation though
high-end motherboards normally have the most phases
and the highest efficiency components
which means the vrm temperatures should be really low
but these motherboards also have the best vrm heatsinks
why purely to look cool mid-range boards
might actually need good vrm cooling but for anything other than extreme
overclocking a high-end board would probably be fine with no vrm heatsinks
at all it's similar to how you'd be fine without a shirt from ltdstore.com but
definitely look cooler with one now that the CPU has power how does it
talk to the rest of the system this copper wire represents how far an
electric signal can travel in a nanosecond
oh everything falls at 5000 megahertz your RAM can send data every 0.2
nanoseconds in that amount of time an electric signal can travel
this far so then this
is physically impossible RAM makers have lied to you although on
your RAM stick in the BIOS and in Windows your RAM will say it's running
at 5000 megahertz or whatever in reality it's completing 5
mega transfers per second what's the difference well since it's ddr or double
data rate RAM transfers are done on both the beginning and the end of each
individual hertz this means the sticks are actually running at 2 500 megahertz
which is why if you've ever looked in CPU-z the RAM shows up as half of what
everything else claims it is depending on what you want to do with your
motherboard knowing how the CPU and the RAM connect can be important like have
you ever wondered why the manual always says to put the RAM in the second and
the fourth slots on your motherboard for this example we'll be looking at a CPU
with dual RAM channels this is the most common configuration
for consumer cpus but the same basic principles apply to workstations or
server processors with more channels the absolute best case scenario for a dual
channel CPU is to simply have two RAM slots
pcb traces go directly from the controller to the RAM stick with nothing
else in the way this is why ASUS's top tier gaming boards only have dual slots
and also why some itx motherboards like this one can punch way above their
weight class when overclocking RAM moving on to motherboards with four RAM
slots here you have two main options t
topology and daisy chaining t topology is when the traces to each
RAM stick on a channel are the same length which can be great for running
all four slots at relatively high speeds but if pure speed is what you're after
then daisy chaining is the way to go with a daisy chain motherboard the
traces basically just go to one slot and then continue on to the next one this
can cause the speeds to be lower when all four slots are used
the timing differences between the two sticks has to be figured out by the controller but it also means with only
two sticks you can run them at nearly the same speed as if there are only two
slots now it is important to use the correct slots though if an electric
signal goes through a wire and the wire suddenly ends with nothing connected to
it like this the signal can reflect back creating
noise in the circuit by putting the RAM sticks in slots 2 and
4 the traces end at the RAM stick reducing noise in the circuit and
allowing for higher speeds so basically before you buy RAM check if your
motherboard has daisy chain or t topology since it determines if you
should get two higher capacity sticks or four lower capacity ones with higher
capacity dims getting cheaper and cheaper it now would make sense for most gaming
motherboards to only have two RAM slots optimized to go as fast as possible our
contact at ASUS agreed but said way too many people will complain that they
can't upgrade their memory in the future even if statistically very few people
actually will do that but even without topologies and slots like if you had the
CPU right next to the RAM and used gold traces or whatever for the perfect
signal there would still be something else holding you back
the memory controller on the CPU everyone has accepted at this point
there's a silicon lottery and some cpus will naturally be able to clock higher
at lower voltages but the same applies to the memory controller on the CPU your
luck in the silicon lottery can sometimes have the biggest effect on how
fast your RAM runs the CPU and RAM are now working but we
still need to be able to connect things like a GPU storage and peripherals in
the past this would be done through the chipset with the northbridge taking care
of PCIe and memory will the southbridge handle i o storage audio usb
you know on modern motherboards though the memory
and some PCIe lanes are connected directly to the CPU while a chipset
handles everything else which simplifies the layout and allows for lower
latencies losing a whole chip is big but what's even more shocking is just how
fast PCIe has become with PCIe 4.0 a one
lane slot can do up to two gigabytes per second and a 16 lane slot is able to
transfer a staggering 32 gigabytes per
second that's close to the speeds of ddr4 RAM how how the heck can they pull
this off simple very expensive pcbs previously it
was possible for lower end motherboards to have only like four or so layers but
now in order to get PCIe 4.0 levels of signal quality 8 to 12 layer pcbs are
basically a requirement given every two layers can come with a 20 to 30 cost
increase for the pcb the insane prices of modern motherboards start to make a
bit more sense even if the majority of users will struggle to saturate a PCIe
3.0 connection let alone 4.0 so you might have noticed
a bit of a theme here one of the most difficult parts of designing a
motherboard isn't creating the best possible product but carefully balancing
the actual value and perceived value
like this motherboard right here supports sli has massive vrm heatsinks
it has four dimms because those are things that people expect it'd probably
be better for the majority of users if there were just two RAM slots closer to
the CPU one PCIe connector and you know
the price of this one down here was turned into better traces and
okay the vrm heatsink it looks pretty cool and
i wouldn't want to give it up but at least i know that that's a trade-off
that i'm making and hopefully in the future we can be more open to crazy
motherboard designs that either deliver higher performance or lower cost huge
thanks to bill zoid for creating the videos used as a reference for the vrm
portion of this video i've got those linked below if you want to get even
more in depth than we did here and also thanks to jj from ASUS for offering some
insight that only a motherboard expert can also let us know down in the
comments if you guys want to see more turbo nerd edition videos and make sure
to hit like this video is only able to go down a couple rabbit holes and there
are so many more here there are also so many
more high quality segways to our sponsor ifixit thank you to icefix for
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ifixit.com LTT if you like this video maybe check out our recent video on the
semiconductor shortage that is making gpus nearly impossible to buy for
a reasonable price at least it won't help you buy a GPU but at least it lets
you go down that rabbit hole