The Road to Solid-State Electric Vehicles – Part Three
By Jim Ringold
The combined head coach and referee are the central computer processor (CPU) of an electric vehicle (EV) such as a Tesla. As we saw in Parts 1 and 2, it took the constant process of inventions and improvements in “solid-state” electronic components to make EV still possible. Previous electric cars needed mechanical switches and rheostats (a true resistor to provide variable current flow) to speed up and slow down an electric vehicle. A rheostat was a very inefficient way of controlling the speed consuming amps of the battery. This technological breakthrough is doubly true for the mainframe that controls everything in a Tesla.
The Tesla Model S, introduced in June 2012, was Tesla’s first “blank sheet of paper” car; a car using Elon’s “First Principles” design philosophy. It started from scratch and gave little weight to what had been done before. Sometimes the current state of technology is the best solution, as in the case of disc brakes. But, generally, the advancement of automotive component design is based on what was used before; can current tools do this; use the current provider; and is it cheap to manufacture? Tesla had an advantage in that nothing had come before. The providers weren’t in place and it wasn’t necessarily the cheapest solution, only the best. So let’s move on to the details of the Model S central processor.
The processor of choice turned out to be made by NVIDIA. We can safely assume that of all available processors this was the best available solution. And it responded to the need, successfully managing the Model S’s systems – the Tegra 3 3D Visual Computing Module (VCM) for the main, vertical, iPad-sized center display; and the Targa 2 VCM for viewing the instrument’s instruments. This Targa system on a chip (SoC) contained eight specialized processors. Model X uses the same components.
This NVIDIA GPU uses a 16 nanometer (NM) size production process. (This will be referenced later in the description of Tesla’s proprietary GPU.) It is physically considered a mid-size processor chip that has a transistor count of 4,400 million. We’ve come a long way since the (single) discrete transistor of the 1950s. NVIDIA started out as a producer of a video graphics processor (GPU) for PC computers with fast, high-resolution products. Video game players loved them. Tesla’s SoC graphics capabilities are required due to video camera inputs, graphical dashboard displays and also audio system control.
In March 2018, Tesla announced an upgraded version of the Media Control Unit (MCU) called 2.0. An older Intel processor was reintroduced when the Atom processor was adopted for graphics. Tesla used this Atom processor to show the faster and improved center display graphics. This upgrade made it possible to display the Tesla Theater and Arcade.
In the refresh of the Model S in 2021, the central touchscreen was rotated horizontally, similar but larger than the horizontal screen introduced in the Model 3 and, subsequently, the Model Y. But back to the CPU / GPU.
As Tesla realized that the “Autopilot” brand of driver assistance was going to need additional computing power to successfully achieve the goal of “Safe Driving”, a more powerful CPU / GPU would be required. Since Tesla was using what at the time was the best NVIDIA had to offer, Elon did what he always did, bring the CPU / GPU design in-house. The result was hardware version 3 (HW3). (For the record, there was an interim hardware version HW2.5 which filled the void until HW3 was ready.)
Elon Musk hired Jim Keller as Autopilot Hardware Manager and used his deep expertise in processor design. He was a legendary portion chip designer who had designed Apple and AMD processors. An AMD computer chip should be designed as a “jack of all trades”, suitable for a large market for use as a processor. This general purpose processor has many features and circuitry that a car specific processor does not need.
So after Elon convinced Jim that he was serious and ready to go the distance with this expensive project, the HW3 was developed specifically for a vehicle application including autonomous driving. Model 3, S and X vehicles with HW2 / 2.5 which had purchased the “Safe Driving” feature have been upgraded to HW3 at no cost to the car owner; a free upgrade on a scale unprecedented in the auto industry – if they could even do such a thing. As evidenced by the “Full Self Driving” beta now available to some “Safe Driving” owners, HW3 is capable of getting the job done.
The new Tesla GPU is, as I understand it, made by Samsung in a modern Korean fabrication shop. When HW3 was needed, the ultimate in a smaller nanoscale chip was then not available from Samsung. Remember, smaller is faster in chips because electrons have less distance to travel. So a smaller chip is faster and, as an added bonus, it is cooler. As Elon and Jim are avant-garde, HW4 was conceived at the same time as HW3. It will be a smaller chip, which would be reduced to 7nm, and which will also be manufactured by Samsung. Samsung is building a new modern manufacturing store in Austin, Texas, near Giga Texas. Again, rumors say the Cybertruck will use HW4 as well as a new camera suite. It is rumored that a modification of the FSD Model S / X vehicles will also come with HW3.
Which brings us to the present day on Tesla’s GPU as we know it. Obviously, there will be faster and better performing specialty processors in Tesla’s future, but we’ll stop here so as not to further demoralize Tesla’s competition.
One more thing: Tesla is spending the extra money to put its GPU on a fighter-grade printed circuit board (PCB). And like a fighter, reliability is super important with fully autonomous driving. To this end, Elon placed two of the HW3 GPUs on the PCB. always looking over the shoulder to ensure 100% processing reliability. Even a Boeing 747 doesn’t have redundant processors!
Then in the fourth part: why the rheostat had to be replaced to have a practical, reliable and efficient EV. Again, semiconductor technology had to advance and come to the rescue.
It’s harder than it looks. Electronic circuit diagram of the first model 3:
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