NVIDIA's Rubin platforms are rumoredly facing design/spec issues, making way for the competition, such as AMD MI500, to get the headstart with HBM4E in 2027.
Will AMD Beat NVIDIA In The Race To HBM4E? Design & Spec Changes In Rubin Platforms Can Give MI500 The Lead
Based on recent reports, NVIDIA's upcoming Rubin and Rubin Ultra platforms are undergoing serious design and spec changes. These changes come ahead of the expected launch of the Rubin generation, which is going to uplift AI performance miles above Blackwell with new features, efficiency upgrades & brand new architectures.
As per the rumors, NVIDIA is facing five critical challenges for the Rubin and Rubin Ultra platforms. These include speed and capacity drawbacks of HBM4 memory, yields, and warpage issues, multi-power design pushback, and redesigning of the heatspreader.
HBM4 Speeds Scaled-Back
Starting with the HBM4 challenges, NVIDIA's Rubin platform features 288 GB of HBM4 memory with up to 22 TB/s of total bandwidth. Micron has already announced volume production of 12-Hi HBM4 memory to power NVIDIA's Rubin platforms, offering up to 2.8 TB/s of bandwidth per stack of 22.4 TB/s across eight HBM4 stacks.
It is stated that NVIDIA is facing challenges in getting higher-speed memory to work with Rubin due to poor base die quality from Micron and SK Hynix, which can lead to a design change or a potential delay in the production cycle.
HBM Stacks Go Down, But Still A Big Upgrade Over Standard Rubin
For Rubin Ultra, NVIDIA had originally pushed for up to 1 TB of HBM4E memory using 16-Hi stacks. But this design is being scaled down to 12-Hi due to yield problems related to Micron and SK Hynix volume production plans. The Rubin Ultra platform has 16 HBM4E sites, 8 per GPU chiplet, so that's 64 GB of 16-Hi capacities per stack. A reduction to 12-Hi will lead to 768 GB of HBM4E memory, a 25% reduction vs the original design, but a 2.66x capacity boost over the standard Rubin chips.
Quad-Chiplet Turns Into Dual-Chiplet
In addition to HBM capacities/speeds, the NVIDIA Rubin Ultra platform is also reportedly seeing a scale-back in terms of design. This was hinted at previously. As per the new changes, Rubin Ultra is reported to go from a 4-die per GPU solution to a 2-die per GPU solution. Rubin Ultra will still feature both single and dual-chip variants, but each of these chips is expected to be scaled down to 2-chiplets versus 4-chiplets.
The reason for these changes is said to be due to severe yield and warpage issues, which are expected in such extremely dense designs with MCP (Multi-Chip Package) approaches. Rubin Ultra will be made using TSMC's CoWoS-L packaging technology. This chip-level change can result in a huge reduction in compute performance and capacities, but NVIDIA is expected to retain the same level of performance as disclosed in its initial announcement.
This will be achieved through board-level assembly, where NVIDIA will incorporate Rubin Ultra GPUs in a 2+2 configuration, which will result in each Kyber server housing four Rubin Ultra GPUs. You can note in the prototype shown during GTC 2026 that the Rubin Ultra rack houses four Rubin Ultra GPUs. The Ultra chips look more squarish than the original rectangular design, which hints at a standard 2 die and 8 HBM site config.
Heatspreader & Power Changes
Lastly, NVIDIA is said to be updating the heat spreader design for Rubin GPUs, which has resulted in a production delay. The original plan was for mass production to commence this quarter, but since the chip specs have changed, the heatspreader has also been moved from a dual Heat Spreader layout to a single Heat Spreader layout.
Reports allege that the dual Heat Spreader design failed to meet the warpage requirements when the AI powerhouse chip entered high-volume production stages. As per the name timeline, Rubin Ultra will see Qualification Samples produced in July, Production Samples in August, and Mass Production is expected in September, with Racks to be ready by October.
The standard Rubin GPUs are also said to be facing instability with the current indium-graphite TIM, and will be switching to traditional graphite TIM for the originally planned 2300 and 1800W platforms.
The Next Big AI Battle: Rubin Ultra vs MI500
NVIDIA's Rubin Ultra and AMD MI500 are direct competitors to each other in the race to AI supremacy. Both of these chips will be the first from each company to go big on co-package optics (silicon photonics) and also feature massive upgrades over existing designs.
As per the current timeline, AMD's MI500 platform is expected to launch around the second half of 2027, offering 2.5D/3D packaging and a 4-die layout with 12-Hi HBM4E memory packages. Rubin Ultra is rumoredly scaled back to a 2-die package with the same 12-Hi HBM4E memory packages, & is expected by 2027-2028.
Although these rumors align with prior reports, NVIDIA's supply chain partners have shown speed in fixing and addressing most issues with its AI platforms in a timely fashion. NVIDIA's Blackwell & Blackwell Ultra also faced chip and rack-level design adjustments, but were able to hit volume production on time & offered specifications/performance on par with what was originally announced.
We expect NVIDIA Rubin & Rubin Ultra platform issues to be mitigated or fixed very soon, allowing NVIDIA to hit its roadmap goal and deliver a substantial uplift to disrupt the AI segment once again, though the competition in the space is getting brutal each passing day.
News Sources: 駿HaYaO #1 , 駿HaYaO #2 , Jeff Pu , Jukan
About the author: A Software Engineer by training and a PC enthusiast by passion, Hassan Mujtaba serves as Wccftech's Senior Editor for hardware section. With years of experience in the industry, he specializes in deep-dive technical analysis of next-generation CPU and GPU architectures, motherboards, and cooling solutions. His work involves not only breaking news on upcoming technologies but also extensive hands-on reviews and benchmarking.
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