TLDR
- Cerebras Systems stock dropped about 7% on September 30 after a SemiAnalysis report.
- The report claims OpenAI’s new GPT-6.1 Sol Ultrafast model runs on Nvidia chips, not Cerebras hardware.
- OpenAI is Cerebras’ largest customer by revenue backlog.
- The new Ultrafast tier reportedly runs near 300 tokens per second, down from 750 with the prior model.
- Cerebras shares are now trading closer to their 52-week low than their 52-week high.
Cerebras Systems stock fell about 7% to $181.40 on Wednesday. The drop came after semiconductor research firm SemiAnalysis posted that OpenAI’s newest flagship model is not running on Cerebras chips.
The post said GPT-6.1 Sol Ultrafast is instead being served on Nvidia hardware. That could include Blackwell-class chips such as the GB300.
Neither Cerebras nor OpenAI responded immediately to requests for comment. Without confirmation, some uncertainty remains about the exact setup.
Why This News Stings
OpenAI is Cerebras’ biggest customer by revenue backlog. Losing ground with that one client carries outsized weight for the stock.
The timing also matters. In August, Cerebras announced it would power the Ultrafast tier for GPT-5.6 Sol at speeds up to 750 tokens per second.
That was framed as a signature win for the company’s Wafer-Scale Engine chips. The new GPT-6.1 Sol Ultrafast tier, unveiled at OpenAI’s DevDay on September 29, reportedly runs at only around 300 tokens per second.
That slower figure has raised questions about whether the larger model is testing the limits of Cerebras’ on-chip memory design. It’s the kind of technical detail that normally stays in the background, but not this week.
A Stock Already Under Pressure
Wednesday’s drop didn’t happen in a vacuum. Cerebras has faced a rocky run since its IPO priced at $350 back in May.
The company posted a GAAP net loss of $450.5 million in its most recent quarter. Insiders have also sold roughly $266 million in stock over the past three months.
Shares are now trading much closer to their 52-week low of $160.81 than their 52-week high of $386.34. That gap says a lot about how sentiment has shifted since the IPO.
The broader market gave Cerebras no cover on Wednesday either. The S&P 500 was higher on the day, and the Nasdaq climbed 0.9%.
That made Cerebras one of the clearer underperformers in the chip sector for the session. Nvidia, meanwhile, moved in the opposite direction, up about 2%.
There’s also a version of this story where nothing has actually changed long term. Cerebras could still end up powering later versions of Ultrafast mode once capacity or optimization issues get sorted out.
For now, though, the market is trading on the headline, not the hypothetical. And the headline is not a good one for Cerebras.
As of Wednesday morning, Cerebras stock sat around $181.40, down from its 52-week high of $386.34. No further comment has been issued by either company on the reported hardware switch.
Stop guessing and start investing with confidence. KnockoutStocks gives you the AI insights, market intelligence, and stock research you need to spot opportunities, cut through the noise, and make smarter investment decisions — all in one powerful platform.
Sign up today and get 50% OFF full access to our premium stock picks.
Simply use coupon code SPECIAL50 at checkout to claim your exclusive discount.
Get 3 Free Stock Ebooks
Discover top-performing stocks in AI, Crypto, and Technology with expert analysis.
- Top 10 AI Stocks - Leading AI companies
- Top 10 Crypto Stocks - Blockchain leaders
- Top 10 Tech Stocks - Tech giants
