Thread by @greentheonly

I am sure you are all eager to know more about HW4, so I am going to show you the refreshed car computer from a Model X. Just don't tell anybody you saw it, because it's really a secret still.
This unit made appearance at the EPC about a month ago, but the picture was hidden.

Looks like Tesla started to build cars with it but does not deliver them yet, I imagine the plan is to announce on March 1st that all cars off the line are already having it.

To start with sorta bad news, The form-factor is totally different, so definitely no retrofits on this one.
top/left is new unit, bottom - current plaid unit)

Now to the actual meat:
Infotainment was reworked compared to current units. The GPU is now on the same board, so no more GPU daughterboard. This makes the whole unit thinner, otherwise no changes there - same 256G NVMe and 16G RAM, same AMD CPU and GPU.

HW4:
A lot less improvement than many hoped for.
Still Samsung Exynos-IP based.
Bumped CPU cores from 12 to 20 (5 clusters of 4 cores each), maxing at 2.35GHz, idle at 1.37GHz
Number of TRIP cores increased from 2 to 3, 2.2GHz max freq
All x2 since there are two SoCs per board

Some internal blocks were renamed. SCS -> SSS, SMS -> SGK and I imagine we'll get an earful about how much more secure the whole system becae as the result because they are not just signing, but also measuring execution now. Also about how everything is encrypted 🙃

DeviceTree: pastebin.com/7xR10YPZ

They are using Linux kernel 5.4.161-rt67 (hopefully they'll be quick with their GPL obligations, HW3 - they are still in violation for the longest time). Coreboot is also in use (hopefully thoe patches are also coming out soon)

Redundancy is the name of the game this time? The board is mostly symmetric, identical power connections on each side. There's even two network links to infotainment. Yet... is you unpower the A side, that kills the network switch and the link is lost. Still the improvements.

Sensors:
There are now 12 fully populated camera connectors. One is marked "Spare", though.

So make that 11 cameras? The names are a bit cryptic, but looks like side cams are in front fenders now. Rumors of two cameras in the windshield are confirmed (properties unknown).
The cameras are: F-SVC, L-SVC, R-SVC

L-FF-Rear, R-FF-Rear (in front fenders I guess)
Selfie,

Wide, Main, Backup
L-FF-Side, R-FF-Side (migrated from pillar to front fender?)

What's SVC you might wonder? According to EPC, SVC is bumper. So I'd guess these are bumper cameras. There's a huge blindspot upfront on legacy cars up front (welcome to the legacy camp, Plaid owners!), so front bumper camera and two in the (rear?) bumper corners for x-traffic

alerts (esp. with pillar moved forward)?

New GPS module with triband antenna.
The unit itself is big and unmarked, so who makes it is unknown, I would not be surprised if it's somewhat custom Tesla thing. They carry bootloader for it in firmware.

Radar: Yes, there's now the bespoken Phoenix radar (yes, of course there is and yes that's what it's called in the properties too). There's also the radar heater of course.

Side by side hw3 (top) and hw4 (bottom) boards:

Power consumption at idle is about double from HW3 based on my measurements and those power pins are pretty massive. which makes the "Input 16V@10A" label somewhat suspect.

What about Model3 you might ask? Well, I have not seen anythign about Model3 upd
ates just yet, but I don't think they are far behind, esp. with news of retoolin
g in China just coming today.

I would also like to say special thank you to people that help me satisfy my curiosity by various means including hardware donations, useful advice and such. I really appreciate all of you!

higher res images of boards
imgur.com/a/gAsbkXV