You don't need an electron microscope to discern large-scale repeated structures like CPU and GPU cores, or to tell the difference between random logic and highly regular memory arrays (usually cache, but sometimes you can see microcode or register files if you look at a small enough area). An electron microscope is only useful if you want to fully reverse-engineer the entire circuit schematic, but that's overkill for basically any purpose except manufacturing your own clone.

So none of the underlying layers matter much for the large and intermediate scale structures?

With the right camera modifications, you don't have to remove any layers from a chip to discern the core count: https://www.flickr.com/photos/130561288@N04/48258310027/ That's an IR photograph taken with a Sony APS-C camera that the IR-blocking filter has been removed from. That's enough to make out the cores and L3 cache slices. (The rest of Fritzchens Fritz's flickr uploads are worth checking out too, especially the video showing how he preps a die for visible light photography.)

That’s cool! How would the major companies reverse engineer these chips?

TechInsights employee here.

The chip design and fabrication firms have their own internal RE divisions mostly to QA their own chips. They do competitive RE, but its often less expensive for them to get a subscription to TechInsights. Economies of scale and all that.

In terms of how its done, its very proprietary. I can tell you it involves clean rooms, ion beams, electron microscopes, chemistry, and bleeding edge software.

If you want to come work for us (its enjoyable, you should :) ) check out our careers page. We are hiring like crazy in many positions.

https://www.techinsights.com/about-techinsights/overview/car...

Why not underestimate the engineering effort, could the problem is higher up in the chain (software api like Apple os) and lower (the equipment to produce the chip). Would the IP that important?