SemiAnalysis report on Rubin Ultra

Research evidence excerpt

SemiAnalysis report on Rubin Ultra

SemiAnalysis report on Rubin Global Markets Research 30 June 2026

Ultra

EQUITY: JAPAN ELECTRONICS

Research AnalystsImpact on industry and points to watch after

Japan electronic partsRubin Ultra

Manabu Akizuki - NSC

manabu.akizuki@nomura.comQuick Note +81 3 6703 1185

Rubin Ultra reportedly to have dual-die design: Interposer size was an issue

SemiAnalysis reported that the planned quad-die Rubin Ultra GPU has been canceled

and will only be a dual-die design. While we have not confirmed the accuracy of the

report, our understanding is that the company had been considering packing four dies on

each interposer for the Rubin Ultra, and switched to two dies per interposer due to

warping issues on the interposer, and was considering achieve a quad-die structure by

connecting two modules via a package substrate directly below the interposers. We think

it would be difficult for a quad-die GPU configured in such a way to be achieved, as it

would lengthen the distance between dies, and increase heat generation and power

consumption. Below, we look at the implications assuming a two-die design has been

adopted.

Focus on one-time impact on industry and quad-chiplet accelerators expected to

appear in 2028

First, if TPUs are not used, we think it will slightly slow progress with advanced large pre-

training models at AI labs. Labs often wait for the emergence of the high-performance,

latest-generation GPUs before training advanced large models, and we think the model

development cycle could lengthen somewhat if the pace of improvement in GPU

performance slows. We think expectations for improved performance of TPUs will rise in

relative terms.

Second is the impact on components. The package substrate surface area of Rubin Ultra