Without any loud announcements (except Elon Musk’s Twitter account), Tesla Motors rolled out Autopilot version 8.1 to 1,000 vehicles Dec. 31, and after verifying any lack of on-road issues, the company will roll it out for everyone in a couple of days, likely Thursday. This update is only for Tesla vehicles manufactured since late October 2016.

In a string of tweets and replies over the last few days, starting with one on Dec. 29, Musk revealed the progress with the update he refers to as “HW2,” short for “hardware 2,” a moniker for the latest generation of vehicles being manufactured by the company.

In another tweet, replying to someone asking about a speed update to the P100D version, which already made the Model S the fastest car in the world, Musk said the performance upgrade will roll out Thursday, since it is linked to the Autopilot upgrade.

But the large number of Tesla owners whose vehicles are “HW1” — manufactured early October 2016 or before — will have to wait till late January for the Autopilot 8.1 update. It will be rolled out along with a Linux kernel update, which is presumably needed for supporting the new version of Autopilot.

It is still not entirely clear what changes the update brings to the vehicles, but we will find out soon enough.