Tesla's (TSLA) custom self-driving chips will be rolled out to older vehicles soon, according to CEO Elon Musk.

On Twitter late on Sunday evening, Musk said that Tesla will begin upgrading older cars with the chip, referred to as the FSD (full self-driving) computer, by "end of Q4, most likely." He added in another tweet that vehicles produced in the "last few months" have been manufactured with the new chip.

All HW2+ cars are upgradable to full self-driving capability with Tesla FSD computer & all production in past few months has FSD computer

— Elon Musk (@elonmusk) July 8, 2019

The 'HW2+' refers to the self-driving chips manufactured by Nvidia (NVDA)  that were installed in earlier Teslas.

Musk has said previously that all Tesla cars produced now are capable of full self-driving, a controversial and not yet available software update that is nonetheless sold to Tesla buyers for $6,000. According to Tesla, the custom chips will be available as an upgrade to buyers who opted in to the self-driving package. 

Musk told investors at Tesla's autonomy day event in April that Tesla's custom chip is the "best chip in the world" for self-driving cars, far exceeding others like Nvidia's Xavier system. In an interview with The Verge, Nvidia's director of automotive Danny Shapiro disputed that claim as "not accurate." 

At the April event, Musk also said that Tesla cars with the FSD system will comprise a fleet of "over one million" robotaxis by the end of 2020, and he reiterated that claim in a follow-up tweet on Sunday evening. Musk also said that the price of Tesla cars would go up "significantly" once they were able to function as robotaxis. 

Tesla shares were down 1.1% on Monday and are down roughly 31% year to date.

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