Ashok Elluswamy, Tesla’s Autopilot director, commented on our article and gave additional insight into how Tesla was able to add support for HW3 and what they’re working on next. He confirmed that Tesla’s FSD team was able to achieve similar performance between AI4 and HW3 with FSD V12.5
Similar Performance, Smaller Model
One of the key points Ashok mentioned was that HW3’s FSD 12.5 release has similar, but not exactly the same performance as the AI4 release. This appears to be due to the smaller AI model for HW3, which has been compute-constrained by memory and speed limitations.
Of course, Ashok also tells us to mind the fact that the parameter counts and size of the AI model aren’t exactly everything. Hardware 3 still has the advantage of being the primary focus of Tesla’s FSD teams until the new Supercomputer Cluster at Giga Texas comes online. That, plus the tremendous reams of data that Tesla has acquired from Hardware 3 vehicles on the road today means that the current Hardware 3 version of FSD V12.5 is probably in a pretty good spot.
Larger Model Coming to HW3
It looks like the Tesla FSD team is working on emulating AI4 in Hardware 3 now, as there are some unique hardware-based operations supported on AI4, that aren’t supported on Hardware 3. Ashok says that in order for Tesla to support the larger model on HW3 they’ll need to implement these AI4’s hardware features with software on HW3. He confirms that Tesla is actively implementing and verifying these operations and they plan to support the larger FSD model on HW3 in the future.
Right now it sounds like Tesla is compressing the model, but still able to get close to the same FSD performance of AI4.
We’re looking forward to seeing FSD 12.5 hitting HW3 vehicles in the upcoming weeks if all goes well with initial employee testing.
We were able to achieve similar performance as the AI4 12.5 release with a relatively smaller model for AI3. Deploying the larger model requires us to implement a few kernels in the compiler to emulate the same operations that are natively supported on the AI4 hardware. The team…
One of the keys here is Ashok has focused on mentioning that the same FSD V12.5 model can run on both hardware platforms in the future. He noted that the performance was similar, but not the same. We’re not quite sure how big the difference is going to be just yet, but it looks to be negligible – especially from the positivity behind his post.
Ashok also doesn’t mention FSD V12.6 or future major iterations of FSD, but we aren’t worried. It sounds like Tesla is still committed to supporting HW3 in future iterations of FSD working, so it looks like it’ll be in a good spot for the foreseeable future.
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Tesla’s been on a roll with Supercharger improvements lately, from the 325kW charging update for the Cybertruck, to 500kW with V4 Superchargers coming next year. While those improvements have been limited to the Cybertruck, Tesla didn’t put all their focus on their new flagship vehicle, but looked at their more affordable vehicles as well.
LFP Battery Heating
Tesla’s Superchargers can now heat LFP Batteries - those that are in the Model 3 and Model Y Rear Wheel Drive variants. This applies to Long Range and Standard Range models, which saw a limited run. This is another update included as part of the 2024 Tesla Holiday Update - which really arrived with a lot of unannounced new features and capabilities.
The change is pretty interesting - Superchargers of the V3 and V4 variety can now pre-heat batteries for Model 3 and Model Y vehicles equipped with LFP battery packs. That means those vehicles are able to get back on the road faster when it's extremely cold. Of course, Tesla still advises you to precondition before you arrive, saving drivers time and money.
Max de Zegher, Tesla’s Director of Charging, also commented on the new feature. Essentially, Tesla is inducing an AC (alternating) ripple current through the battery to warm it up. Keep in mind that Superchargers are DC charging. That means it is possible to get a cold-soaked LFP vehicle on the road 4x faster than before, assuming that it didn’t precondition at all and that it is in the worst-case scenario (below 0ºF).
In essence, Tesla is using some engineering magic to turn the circuits inside the LFP battery into an electric heater - and powering that heater through the Supercharger. An AC ripple current is a small oscillation in the DC charging current that generates heat through electrical resistance, warming up the battery. Those ripples are a byproduct of converting AC to DC and back - so Tesla is using the onboard charger to induce those ripples to warm up the battery. Definitely an innovative technique that’s really only possible with the versatility of the NACS connector.
We’re hoping Tesla can implement this across their full lineup of vehicles, but we’ll have to wait and see how it is trialed across LFP vehicles first and if it is even possible on vehicles with 2170 or 4680 battery packs.
Tesla launched two FSD updates simultaneously on Saturday night, and what’s most interesting is that they arrived on the same software version. We’ll dig into that a little later, but for now, there’s good news for everyone. For Hardware 3 owners, FSD V12.6.1 is launching to all vehicles, including the Model 3 and Model Y. For AI4 owners, FSD V13.2.4 is launching, starting with the Cybertruck.
FSD V13.2.4
A new V13 build is now rolling out to the Cybertruck and is expected to arrive for the rest of the AI4 fleet soon. However, this build seems to be focused on bug fixes. There are no changes to the release notes for the Cybertruck with this release, and it’s unlikely to feature any changes when it arrives on other vehicles.
FSD V12.6.1 builds upon V12.6, which is the latest FSD version for HW3 vehicles. While FSD V12.6 was only released for the redesigned Model S and Model X with HW3, FSD V12.6.1 is adding support for the Model 3 and Model Y.
While this is only a bug-fix release for users coming from FSD V12.6, it includes massive improvements for anyone coming from an older FSD version. Two of the biggest changes are the new end-to-end highway stack that now utilizes FSD V12 for highway driving and a redesigned controller that allows FSD to drive “V13” smooth.
It also adds speed profiles, earlier lane changes, and more. You can read our in-depth look at all the changes in FSD V12.6.
Same Update, Multiple FSD Builds
What’s interesting about this software version is that it “includes" two FSD updates, V12.6.1 for HW3 and V13.2.4 for HW4 vehicles. While this is interesting, it’s less special when you understand what’s happening under the hood.
The vehicle’s firmware and Autopilot firmware are actually completely separate. While a vehicle downloading a firmware update may look like a singular process, it’s actually performing several functions during this period. First, it downloads the vehicle’s firmware. Upon unpacking the update, it’s instructed which Autopilot/FSD firmware should be downloaded.
While the FSD firmware is separate, the vehicle can’t download any FSD update. The FSD version is hard-coded in the vehicle’s firmware that was just downloaded. This helps Tesla keep the infotainment and Autopilot firmware tightly coupled, leading to fewer issues.
What we’re seeing here is that HW3 vehicles are being told to download one FSD version, while HW4 vehicles are being told to download a different version.
While this is the first time Tesla has had two FSD versions tied to the same vehicle software version, the process hasn’t actually changed, and what we’re seeing won’t lead to faster FSD updates or the ability to download FSD separately. What we’re seeing is the direct result of the divergence of HW3 and HW4.
While HW3/4 remained basically on the same FSD version until recently, it is now necessary to deploy different versions for the two platforms. We expect this to be the norm going forward, where HW3 will be on a much different version of FSD than HW4. While each update may not include two different FSD versions going forward, we may see it occasionally, depending on which features Autopilot is dependent on.
Thanks to Greentheonly for helping us understand what happened with this release and for the insight into Tesla’s processes.
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