Probing Pi 5 silicon with an Electron Microscope!

The Raspberry Pi 5 can't be overclocked past 3 GHz. Why? The secret is hidden in the silicon deep inside.

X-rays don't go deep enough. This video explores modern CPU architecture, clocks and PLLs (Phase-Locked Loops), silicon die shots, and even transistor-level debugging with an electron microscope!

Mentioned in this video:

Contents:

00:00 - Human DNA on my chip?
00:42 - Overclocking, featuring actual clocks
05:59 - Heat is not an issue (unless you're a candle)
07:14 - Die shots: OCP on the Pi 5's BCM2712
11:51 - Die shots: RP1
12:37 - Probing individual transistors at 16nm
18:35 - Peering deeper inside silicon
20:06 - Learning more...

[JohnneyleeRollins]

Magic smoke is what I keep in my computers

[dancoberley]

As a U.S Navy trained electronics technician, I've been around long enough to see magnetic amplifiers in action, but it blew me away to see those inductors on the metal layer. We've come a long way in 40 years. Nice job Jeff.

[ToumalRakesh]

Inside your computer are millions of tiny bees doing math, so you don't have to!

[dfs-comedy]

This is amazing. From 1996-1999 I worked for a company that reverse-engineered ICs. I wrote software to help image the chips and assist with their reverse-engineering. But the state of the art in 1999 was 140nm. So smaller than visible light, but not all that much smaller and it was still practical to use optical microscopes even to see individual transistors.

Of course, our reverse-engineering was destructive because we took photos of each chip layer (top metal, next metal, etc) and then etched it off to clearly see the next layer.

I recall one project, however, where they contracted someone with a focused ion beam machine to deposit new metal wires on a broken chip to repair access to onboard flash memory that they could then read out. Even at the time, it seemed science-fictiony.

[stupiduser]

A friend and I swapped a clock crystal with one from a TV in a Commodore 64 in the 1980’s. Lode Runner never ran so fast. Then the computer made magic smoke. Cooling wasn’t something we considered until it was too late

[manuellongo]

These deep dives into chips are truly amazing and the people who design them are even more amazing. I remember in the 90's having a pleasant chat with a chip designer and was open-mouthed. What was done back then was nothing next to today's capabilities. Back then I was really impressed....today I don't even know what term to use.

[DrathVader]

Those probes are amazing. They go from a very much human scale too all the way down to nanometer sized tip

[bituniverse]

Watching that electron microscope come into focus was magical. Insane what tools we have.

[HapppyMann]

As a factorio addict this video was a trip!

[Genesis]

Your explanation of clocks reinforced the (joke?) that we tricked a rock into thinking with computers. :) Happy Pi Day too!

[greentravels]

That was a lot of good background information. Thank you, and those who helped you, to bring us a deeper dive into silicon. I had a good chuckle at Red Shirt Jeff getting his fire on!!

[harrysnell]

Really like the die shots. The inductors at 9:44 are much more likely to be part of an oscillator in a PLL (typically in a transceiver, which requires a very stable PLL that often uses inductors) or an RF circuit, rather than filtering power. That's also why you see them round them corners since they are high speed I/O.
And metal fill is to keep the layers flat during polishing, more so than timing.

[MichaelKlements]

Replacing the oscillator was the first thing that came to my mind, I'm glad you covered why this probably wouldn't work. I've also been quite impressed by the performance of the standard Pi 5 active cooler, it's even kept my overclocked Pi 5 well under thermal throttling. Fascinating video!

[JohnDlugosz]

Just to be clear: the "15nm" doesn't actually refer to the size of anything. Manufacturers have long given up the original meaning of "feature size" and now it's just a marketing label.
Since you are actually visualizing individual transistors, it would be interesting to make a measurement in the micrograph to see what are the actual dimensions of normal transistors.
They do vary in size, though, with some being much longer in one direction.

[MarcoGPUtuber]

What's inside my computer are electrons doing their thing needed to play another amazing Jeff Geerling video.

[vincei]

Excellent content, Jeff. Thanks for the trip down the rabbit hole.

[stalthyone]

Insightful and concise as always, Jeff. Thanks for always giving us your best and never half-assing your content. It's greatly appreciated.

[owlmostdead]

At 4:19 there is a very high frequency noise, kind of hurt with headphones on

[MoChuang]

EM is pretty freaking amazing. I’m a biochemist and we can study proteins down to about 6A resolution in their native folded state using cryo-EM. 6A is 0.6nm and very close to the size of a single carbon-carbon bond. The cryo part is used to freeze a solution of pure proteins down to near zero kelvin to prevent any vibrations in the sample. So yeah these things are built away from trains and highways with buildings built up specifically to minimize ground vibrations.

[jamesdecross]

Well, Jeff, I'll tell you what… the next time you are over here, in the UK, and visiting the World's only Raspberry Pi Store once again, you MUST take a little detour to the edge of town and visit the Cambridge Museum of Technology where, in the Pye Building – a small hut out the back of the Victorian Pumping Station (which houses the museum) run and managed by the Cambridge Industrial Archaeology Group, you'll find a display explaining just how the Cambridge Scientific Instruments Company played their part in the development of those Scanning Electron Microscopes. They even have two original machines on display, although I do wonder the last time was that anyone tried to switch one on! These machines look like Mini Mainframes from back in the day. Quite amazing!