Prática de Shadowing: Why Memory Prices Are Crazy High - Aprenda a falar inglês com vídeo

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This is a graphics card for home gaming, the RTX 5090.

On its board, the first thing you see is the GPU in the middle.

Around the GPU is a ring of video memory chip.

When the GPU is working, its instructions, data, and temporary results are stored here.

And this is one compute node in NVIDIA's GP300 AI data center system.

The node has four GPUs.

But around them, we cannot see memory chips like the ones on the 5090.

So can AI server GPU work without video memory?

Of course not.

Look closely.

Next to the four GPUs are two rows of small squares.

These are the memory chips.

But unlike the memory on the gaming card, they are not placed on the board by themselves.

They are packaged together with the GPU.

And this special kind of memory is the star of today's video, HBM.

HBM uses 3D stacking to give it a high bandwidth and pack more parts into a small space.

It is now a key part of high -end AI graphics card.

It's also one of the main reasons normal memory prices have gone up recently

so how does hbm work

and how is it made in this video we are going

to learn all about hbm hi everyone i'm richard from htx

studio this video was originally made by right not a very

talented chinese content creator with his permission we translate it into

english for you guys we hope you enjoy it hbm stands for high bandwidth memory.

Bandwidth means how fast data can be moved.

So high bandwidth simply means that data can move very fast.

The memory chips and the GPU are connected by wires.

They use voltage signals to send data.

For example, let's say we want to send this data 0 1 0 1 0.

We can use high voltage for 1 and low voltage for 0.

So the voltage on the wire becomes low, high, low, high, low.

If want to send the data faster we can make each

voltage state last for last time we make this low high

low high low become this low high low high low in other words we erase the frequency

but frequency is not the only way to move data faster we can also add more wires

and send different parts of the data at the same time

this increases the bus width bandwidth equals frequency times spot width

so to get more bandwidth we can raise the frequency increase the bus width

or do both But raising the frequency of video memory causes many problems.

The voltage on the wire cannot go from low to high in no time.

It also cannot go from high to low in no time.

The change takes time.

We must wait for the voltage to fully rise or fall before the next cycle can start.

So frequency has a clear limit.

A higher frequency also causes more noise between nearby data lines.

That is why HBM uses a very wide bus to get more bandwidth.

A normal GDDR7 memory chip like the ones on the RTX 5090 has a bus width of 32 bits.

The 5090 can use up to 16 of these memory chips.

That gives it a total bus width of 512 bits, but one HDBM3 memory stack has a bus width of 1024 bits.

This B300 GPU has 8 HDBM3 stacks around it, so its total bus width is 8192 bits.

But how can HBM fit such a wide bus into such a small space?

As we just said, memory sends data to the GPU through wires.

More wires means a wider bus.

One bit of bus width needs one wire for data.

A normal GDDR7 memory chip has a bus width of 32 bits.

This means there are 32 data lines between the memory chip and the GPU.

But in real life, it needs many more lines.

It also needs lines for power, addresses, clock signals, and more.

So a GDDR7 chip can have 266 connection points.

And that is only for a bus width of 32 bits.

HBM has a bus width of 1024 bits.

So it needs 1024 lines just for data.

After we add the lines for power, addresses, and other jobs, one HBM3E stack has 3982 connection points.

So this is HBM's first problem.

How can it fit so many connections into such a small space?

First, let's see how normal GDDR memory is made.

The main memory circuits are made on a thin piece of silicon, but this silicon die is very easy to break.

The contact points on it are also very small, so it is hard to work with and use.

That is why we need a packaged substrate.

It is made from woven glass fiber and epoxy resin.

It is much stronger than the silicon die.

The finished die is turned upside down and placed face down on the substrate.

The contact points on the die connect straight to the substrate.

Inside the substrate are many layers of wires.

They move the signals to the back of the substrate, where larger solder balls are added.

The substrate protects the silicon die.

It also moves the tiny contact points on the die to the back of a much stronger package.

This makes the next step like soldering it onto a circuit board much easier.

To make this kind of substrate, glass fiber cloth is first soaked in epoxy resin.

It is pressed at high heat until it becomes a hard board.

Then a layer of copper foil is placed on both sides to make the circuit.

A light -sensitive film is put on top of the copper.

A mask with the circuit pattern is placed over it.

Then ultraviolet light shines on the board.

The parts of the film hit by the light change.

A developing liquid then washes away the parts that were not hit by light.

That leaves some of the copper open.

The board is then placed in an etching liquid.

The open copper is eaten away, while the copper under the film stays.

This is how the circuit lines are made.

A real packaged substrate usually has four to eight layers.

They are stacked together like pancakes.

Small holes are made with a laser to connect the circuits on different layers.

But this way of making circuits has a big limit.

The circuit lines cannot be packed very close together.

The surface of glass fiber is rough and not flat.

So when the copper foil and the light -sensitive film are pressed onto it, small air bubbles can get trapped inside.

If a circuit line is too thin, one small bubble can break it.

There is another problem.

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This process uses a liquid chemical to eat away the copper.

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But the chemical does not only eat downward.

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It also eats into the sides.

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If a line is too thin, the sides can be eaten away until the line breaks.

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Because of these limits, a normal packaged substrate cannot hold very dense circuit lines.

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And there is one more problem.

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Normal video memory must be soldered onto a PCB.

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The PCB then connects the memory to the GPU.

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A PCB is made in almost the same way as the substrate

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so its circuit lines also cannot be packed very close together.

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But HBM needs almost 4 ,000 connections.

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A substrate made from glass fiber cannot do this.

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Its surface is just too rough.

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We need a new material.

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The material is silicon.

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Yes, the same silicon used to make chips.

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We start with one large piece of silicon.

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Its surface is polished until it is very smooth.

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Then photolithography and etching are used to make very small grooves on its surface.

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Copper is put into those grooves to form circuit lines.

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The HBM chips no longer need to sit on a normal substrate.

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They can be soldered straight onto this large piece of silicon.

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The GPU is also soldered straight onto it.

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Now the HBM and the GPU can connect through this silicon.

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This large piece of silicon which connects the chips together is called a silicon interpulsor.

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A silicon interpulsor is like a chip with no transistors.

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Its surface is even flatter than a mirror.

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This lets chip makers use photolithography, etching, and thin film deposition to make very fine metal lines.

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On a glass fiber substrate, the lines are more than 10 micrometers wide.

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But on a silicon interpulsor, they can be less than 1 micrometer wide.

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They can even be only a few hundred nanometers wide.

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This means the silicon interpulsor can hold tens or even hundreds of times more circuit lines in the same space.

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With the silicon interpulsor, HBM can fit many more connections into a small area.

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And that solves the speed problem.

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But AI chips needs one more thing from video memory, more capacity.

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An HBM stack and a normal GDDR memory chip take up about the same amount of space on the board.

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A GDDR7 chip like the one on RTX 5090 can usually hold 2GB.

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Even if we put 16 of them around the GPU, the total is only 32GB.

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That is enough for gaming, but it is still too little for AI.

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So how can we increase the capacity?

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The answer is stacking.

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We stack several bare memory dies on top of one another.

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They can all use the same silicon interpulsor at the bottom.

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This let us increase the capacity many times without using more space at the bottom.

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But stacking many chips is not easy.

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Putting more than 10 memory chips on top of one another may look simple.

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But there is one big problem.

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How does the chip on top talk to the chip below it?

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Can we pull wires out from the sides of every chip and connect them to the bottom?

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No, every layer would need thousands of wires.

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There would not be enough space on the silicon interpulsor and every wire would have to be very thin.

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Even gold wire cannot hang in the air at such a small size.

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So engineers came up with another idea.

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They make holes in the silicon and fill them with copper.

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Every memory chip connects to these copper columns.

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The data can move down through the columns and reach the silicon interposer at the bottom.

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This is called a through silicon via, or TSV.

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But making these holes is not easy.

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Each hole is only about 5 to 10 micrometers wide a normal drill cannot make a hole this small.

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The industry uses a method called deep reactive ion etching.

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It is also called the Bosch process.

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This is a silicon wafer that already has transistor circuits on it.

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Now we need to make deep holes in it.

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First, we put photoresist on the surface of the wafer.

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Then a lithography machine shines the pattern of the holes onto the photoresist.

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The parts hit by the lights change.

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A developing liquid washes these parts away and opens the silicon below.

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Next, sulfur hexafluorid gas or SF6 enters the chamber.

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A radio frequency coil turns the gas into plasma and makes three fluorine radicals.

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These fluorine radicals react with the open silicon.

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This makes silicon tetrafluorid gas.

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In simple words, the silicon is eaten away.

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But this does not only happen downward.

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It also happens sideways.

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If we keep doing this, we will get a large round space instead of a straight deep hole.

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So after FS6 has been used for a short time, it is stopped.

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Then Octafluorocyte cubitane or C4F8 enters the chamber.

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It is also turned into plasma.

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This makes fluorocarbon radicals.

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They gather on the silicon and form a protective film.

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Then FS6 enters the chamber again.

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But this time, the protective film stops it from eating the silicon.

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When SF6 is turned into plasma, it makes both fluorine radicals and charged ions.

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An electric field guides these ions straight down towards the wafer.

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The ions hit the protective film at the bottom of the hole and remove it.

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Because the ions move straight down, they only remove the film at the bottom.

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The film on the sides stays in place.

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Now the etching glass can keep eating the silicon at the bottom.

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Then the same steps happen again.

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Ash, protect, pit.

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Ash, protect, pit the hole slowly gets deeper.

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A silicon wafer may begin around 700 to 800 micrometers thick, but at this stage, the hole may only be etched about 100 micrometers deep.

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Later, the wafer will be made thinner from the back until the hole comes out the other side, but we do not make it thinner yet.

193

First, we need to fill the hole with copper.

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We use vapor deposition to put a layer of silicon dioxide on the inside wall of the hole.

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This layer is very dense and does not carry electricity.

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It It is like putting a tiny ceramic tube around the copper column.

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It keeps the copper away from the silicon, but this is still not enough.

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Copper items can move around.

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Over time, they can move into the silicon.

200

If this happens, they can damage the crystal structure of the silicon.

201

So we need another layer between the silicon dioxide and the copper.

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This is called a barrier layer.

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It is often made from tantalum or tantalum nitride.

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The layer is only a few nanometers thick, but it can stop copper items from moving into the silicon.

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Next, a very thin copper seed layer is put on top of the barrier layer.

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Then a wafer is placed in the copper sulfate liquid for electroplating.

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Copper ions slowly build up on the bottom and the walls of the hole.

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In the end, copper fills the entire hole.

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The wafer is then ground thinner from the back onto the hole and the copper inside are open.

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Now we have a copper connection that goes through the silicon.

211

This is how one layer is made.

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Next, lithography and electroplating are used to grow tiny copper bumps on top of the open copper columns.

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Their tops are covered with a thin layer of tin.

214

These are called micro bumps.

215

Now we can stack several memory dies together.

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We heat them and press them.

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The tin on the micro bumps melts and solders the layers together.

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Now every chip is connected through the copper columns and the micro bumps.

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Data from the top layers can move all the way down to the silicon interposer.

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At this point, the main memory part of HBM is finished, but the chip is still very easy to break, so we cannot use it yet.

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As we said before, every memory die has been ground down to a thickness of only a few dozen micrometers.

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The thin dies are held up by tiny micro bumps between them.

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It is like a thin sheet of dry seaweed hanging in the air.

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A small force can break it.

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The answer is to fill the spaces between the dies, so they are no longer hanging in the air.

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There are two main ways to do this.

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Only three companies can mass -produce HBM today, SK Hynix, Samsung, and Micron.

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SK Hynix uses the first method.

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It stacks all the dyes first, then it heats the whole stack and solders all the micro bombs at the same time.

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The full stack is put into a mold.

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Liquid epoxy resin is poured into the spaces between the dyes, heat and pressure that make the resin hard.

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Samsung and Micron uses another method.

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They put a thin polymer film between every two dyes.

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Under heat and pressure, the film melts and the micro -bombs are soldered together.

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Then the film becomes hard as it cools.

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They repeat this process one layer at a time.

237

The SK Hynix method works better in two ways.

238

First, it solders the whole stack at once instead of doing it one layer at a time, so it is much faster to make.

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Second, there is nothing else between the chips when the micro -bombs are being soldered.

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This means fewer things can go wrong, so the yield is higher.

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HBM has many chips stacked on top of one another, so heat is a big problem.

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To help heat move out, makers add extra through silicon vias.

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These extra vias do not carry data, they are only used to move heat.

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SK Hynix also mixes particles that carry heat well into the epoxy Ryzen.

245

This makes the epoxy work a little like thermal paste, so their HBM can move heat away about twice as well as Samsung's.

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This has helped SK Hynix became the biggest company in the HBM market.

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Their market share is about 50%.

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With a silicon interposer, HBM can have a bus width of 1 ,024 bits.

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And by stacking memory dice, HBM can hold a lot more data.

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In this GP300 server node, every HBM stack has 12 memory layers.

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Each stack can hold 36GB.

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Each GPU has 8 HBM stacks.

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So that is 288GB for 1 GPU.

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The node has 4 GPUs.

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So it has 1 ,152GB of video memory in total.

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That is more than 1TB in just one server node.

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So how much does one node cost?

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About $300 ,000.

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Today, HBM3E is the version used at a large scale, but companies have already started making HBM4.

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HBM4 has a buzz width of 2048 bits, so it can stack up to 16 memory layers.

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So HBM4 needs even denser connections and an even taller stack.

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HBM4 still uses micro bombs to join the layers, but it may be the last HBM generation to use them.

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As the connections get denser, the space between the micro bombs gets smaller.

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During soldering, two nearby micro bombs may join by mistake.

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This can cause a short circuit, so in the future, HBM may remove the micro bombs.

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Instead, two clean and smooth copper surfaces will be pressed straight together.

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The copper items will move into each other and form one piece.

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This is called hybrid bounding without micro bumps the connections can

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be packed closer together the stack can be shorter heat can move out more easily

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and no epoxy is needed between the layers

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but we still do not know

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which hbm generation will use this technology at a large scale

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a few years ago the plan was to use it in hbm4

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but that did not happen and

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that is all for this video hbm has helped ai grow by giving it the key memory

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and computing base it needs but hbm uses many of the same processes and machines as normal DRAM.

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So making more HPM takes production space away from normal memory.

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This means there's not enough normal memory for everyone who wants it.

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So prices go up.

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Do you believe in the future of HPM?

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Do you believe in the future of AI?

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That's it for this video.

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See you next time.

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Vocabulário e dicas de fala para esta lição

Esta aula de conversação de nível C1 usa o vídeo “Why Memory Prices Are Crazy High”. As palavras que mais se repetem: silicon, memory, hbm, copper, chip. Este vídeo tem 283 frases e 3140 palavras para praticar shadowing. A fala dura 16:58. O falante fala rápido, cerca de 185 palavras por minuto, então espere sons ligados e reduzidos. Apenas 76% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.

Vocabulário principal deste vídeo

As 15 palavras mais avançadas do vídeo, com pronúncia e significado:

Palavra	Pronúncia	Significado
silicon substantivo	/ˈsɪləˌkɑn/	silício
stack substantivo	/stæk/	pilha
substrate substantivo	/ˈsʌbˌstɹeɪt/	substrato
width substantivo	/ˈwɪtθ/	largura
microwave substantivo	/ˈmaɪkɹoʊˌweɪv/	micro-onda
solder substantivo	/ˈsɒl.də(ɹ)/	solda
wafer substantivo	/ˈweɪ̯fɚ/	wafer
bandwidth substantivo	/ˈbændwɪdθ/	largura de banda
voltage substantivo	/ˈvəʊltɪd͡ʒ/	tensão, voltagem
etch verbo	/ɛt͡ʃ/	gravar
micrometer substantivo	/maɪˈkɹɑmɪtəɹ/	micrómetro
bump substantivo	/bʌmp/	estrondo
resin substantivo	/ˈɹɛzɪn/	resina
dense adjetivo	/ˈdɛns/	denso
fluorine substantivo	/ˈflʊ(ə)ɹˌin	flúor

Phrasal verbs que você vai ouvir

Palavra	Pronúncia	Significado
eat away verbo	/it‿əˈweɪ/	comer
go up verbo		subir
move out verbo		se mudar
come out verbo	/ˌkʌm ˈaʊt/	sair, partir
come up with verbo		pensar (em), alcançar

Gramática neste vídeo

As estruturas que o falante mais usa, com as palavras exatas do vídeo:

Estrutura	No vídeo
Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz	are stored · are not placed · are packaged
Present perfect have/has + particípio passado — uma ação passada que ainda importa agora	have gone · has been · has been ground

Pronúncia para ficar de olho

Os sons de “th”: width /ˈwɪtθ/, bandwidth /ˈbændwɪdθ/, lithography /lɪθˈɒɡɹəfi/, thickness /ˈθɪknəs/, cloth /klɒθ/
Palavras longas — acerte a sílaba tônica: micrometer /maɪˈkɹɑmɪtəɹ/, lithography /lɪθˈɒɡɹəfi/, deposition /ˌdɛp.əˈzɪʃ.ən/, ultraviolet /ˌʌltɹəˈvaɪələt/

Sons difíceis para falantes de português:

Consoante final — sem acrescentar um “i” depois: stack /stæk/, substrate /ˈsʌbˌstɹeɪt/, node /noʊd/, bump /bʌmp/, compute /kəmˈpjuːt/
/l/ final — a língua toca o céu da boca, não vira “u”: foil /fɔɪl/, coil /kɔɪl/, particle /ˈpɑɹtək(ə)l/, thermal /ˈθɜːməl/, drill /dɹɪl/

Como praticar com este vídeo

Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
Comece na velocidade 0,75×, faça shadowing frase por frase e volte à velocidade normal quando ficar fácil.
Grave a sua voz e compare com o original, prestando atenção a palavras como silicon, stack, substrate.

O que é a Técnica de Shadowing?

Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.

Técnica de shadowing: leia o guia completo passo a passo →

Prática de Shadowing: Why Memory Prices Are Crazy High - Aprenda a falar inglês com vídeo

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