The early price support generated by SK Hynix's recently announced share buyback has begun to fade, with sell-side analysts simultaneously trimming High Bandwidth Memory (HBM) revenue assumptions. The combination has put renewed pressure on the Korean chipmaker, whose stock had briefly stabilised after the repurchase programme launched.

SK Hynix (Korea Exchange: 000660) is the leading merchant supplier of HBM3 and HBM3E stacks used in NVIDIA's H100 and H200 AI accelerators. Its HBM business drove record profitability through 2024, with the segment contributing a disproportionate share of consolidated operating profit.

What is driving the analyst revisions?

The headline concern, as carried by ad-hoc-news.de, centres on HBM volume assumptions feeding into the final quarter of calendar 2024 and into 2025. Sell-side models had previously assumed continued strong absorption of HBM output by the AI accelerator supply chain, particularly by NVIDIA.

That assumption is now being questioned. Multiple analysts have begun to mark down shipment and revenue figures, according to the report. The revisions cluster around the pace of NVIDIA procurement rather than around aggregate industry demand.

How concentrated is the HBM customer base?

HBM is one of the most concentrated semiconductor product categories. SK Hynix supplies the majority of HBM3 and HBM3E volume to NVIDIA, with Samsung Electronics and Micron Technology splitting the remainder of the merchant market. Any change in NVIDIA's procurement guidance translates directly into revenue-line impact for all three suppliers.

This customer structure is the reason HBM-related revisions typically arrive first at SK Hynix, before later propagating to Samsung and Micron estimates.

Why did the buyback underperform?

Buybacks are mechanically supportive: a listed company deploys cash to retire shares, absorbing supply and reducing free float. The price impact is usually most visible in the first several trading sessions after announcement, before fading as the order book normalises.

The ad-hoc-news headline indicates that this window of mechanical support closed earlier than typical. The interpretation is that the underlying sell-side reassessment on HBM outweighed the corporate bid, leaving the share vulnerable once the repurchase flow tapered.

What does the HBM3E transition mean?

HBM3E is the current-generation product. SK Hynix qualified its 12-Hi HBM3E stack with NVIDIA in early 2024 and has been the primary volume supplier since. HBM3E carries a price premium over HBM3 and over conventional DDR5, which is why mix shifts move revenue assumptions disproportionately for the memory vendors.

The transition to HBM3E is also the basis for the next-generation HBM4 roadmap, with SK Hynix, Samsung and Micron all working on samples for qualification in the 2025-2026 window.

What changes if the revisions stick?

If a material consensus cut to 2025 HBM revenue materialises, the operating-profit impact is amplified by HBM's gross-margin profile. The HBM line runs well above the company's blended DRAM margin, so revenue revisions translate into outsized operating-profit deltas at the consolidated level.

The wider question for the sell-side is whether AI accelerator demand from the hyperscale buyers will sustain HBM order books through 2025. The relevant hyperscalers are:

• Microsoft
• Google
• Meta
• Amazon

Capex commentary from these buyers has been the largest swing factor for memory-related estimates in recent quarters.

Market context

SK Hynix shares had been among the strongest performers in the Asian semiconductor complex through 2024, supported by the HBM narrative. Korean retail and foreign institutional flows both tilted positive through most of the year.

The current softness coincides with a broader recalibration of AI capex expectations across the supply chain. Order books at foundry and packaging partners are also under review as the major buyers signal more measured spending into 2025.