Shares of AMD (AMD) have been on a tear over the last month, gaining nearly 30% to top off strong previous 24 months of trading. While AMD has outperformed the market lately, some analysts are beginning to express concerns over the company’s cryptocurrency mining-driven GPU sales.

Bernstein analyst Stacy Rasgon recently highlighted the limitations of AMD’s GPU sales model, as it relied heavily on miners versus the traditional gaming customer.

Given AMD’s GPUs have been preferred for mining, and GPU supply in general to gamers was constrained industry-wide, we believe it is plausible that much of AMD’s GPU ramp has benefitted miners, rather than gamers, over this period.

In a similar vein, Morgan Stanley’s Joseph Moore expressed his concerns regarding the outlook of AMD’s cryptocurrency strength.

Cryptocurrency strength has to some degree offset the slow and steady progress establishing momentum in desktop and server microprocessors after several years away from those markets — but that higher revenue has driven higher operating expense, which further raises the bar for the processor business if crypto momentum should fade.

In March, Susquehanna, a market research firm, reduced its outlook rating to negative from neutral and lowered its price target for AMD shares, citing impending competition from cryptocurrency mining company Bitmain, maker of the popular ASIC mining hardware that outperforms GPU-mining systems.

These worries are compounded as more competition moves into the industry. Just recently, Intel (INTC) confirmed that its first discrete graphics chip, which will not be integrated into a CPU like its current graphics systems, will launch in 2020.

While the intended core customer base for the new GPUs has not yet been confirmed, Intel executive Navin Shenoy expressed interest in exploring both client and server offerings, according to MarketWatch. The chip is poised to be integrated into products across various markets, including gaming and artificial intelligence.

Nvidia (NVDA), AMD’s main GPU competitor, recently revealed how much revenue it generated from chip sales related to the cryptocurrency market. Driven by a stronger than expected demand from cryptocurrency miners, the company posted revenue of $289 in Q1 from crypto-related sales. However, the company anticipates that number to fall in the coming quarter.