GoKawiilSipearl has been developing a custom CPU, especially designed for high-performance workloads, named 'Rhea', for over five years. In late May, it was finally announced that the company had received the CPU from the fab, initiating the bring-up process, which is a significant milestone. The HPC CPU sports over 80 cores, in addition to an innovative memory subsystem. We spoke directly with Craig Prunty, vice president of marketing and business development of SiPearl, to learn the fine-grained details.
The Rhea CPU is intended to reach markets by late 2026 or early 2027, and won't be the most performant HPC CPU on the market. Regardless, SiPearl told us at Computex that there is interest both towards Rhea and its successors from rather unexpected parties, so the company is in with a chance to become a successful CPU designer over time.
Rhea's long road toward reality
SiPearl's Rhea (or Rhea1, how the company prefers to call the unit these days) sports 80 Arm Neoverse V1 cores with two 256-bit Scalable Vector Extension (SVE) engines for fast vector computations in FP64, FP32, BF16, and INT8 formats; 1 MB of L2 per core; 80 MB system-level cache (SLC), and 104 PCIe 5.0 lanes. The CPU has a unique memory subsystem comprising four HBM2E interfaces for 64 GB of on-package HBM2E stacks for applications that require massive memory bandwidth (think supercomputer applications like fluid dynamics) and four DDR5 interfaces supporting two 256 GB DIMMs per channel, for up to 2 TB of memory per socket. Rhea comprises 61 billion transistors and is fabbed by TSMC using its N6 process technology.
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(Image credit: Tom's Hardware)
SiPearl received the first samples of its Rhea processor in mid-May, and the CPU is currently in bring-up mode. So far, it looks like the very first silicon works just fine, so the company will not have to respin it, which means SiPearl has a good chance of shipping it to customers in the coming quarters.
"The Rhea1 CPU is in its 12-week bring-up process since May 13, and it works exactly as it was designed to do," said Craig Prunty, vice president of marketing and business development of SiPearl, in an interview with Tom's Hardware Premium. "The test version of Rhea1 will be available for testing by partners and EU collaborative projects at the end of the bring-up process. The general availability of Rhea1 is scheduled for end of 2026."
Getting the very first silicon to work correctly is a stroke of good luck, especially for the very first product from a startup that has never designed a complex CPU before. However, it has taken the company over five years to define and then develop its processor, an unacceptably long cycle. With Rhea, SiPearl not only built its processor, but it actually built the company, Craig Prunty admitted in an interview with Tom's Hardware. The company once tried to work with a contract chip designer, but eventually canceled the deal and formed five in-house development teams in Europe. Since these teams have never worked together before, the processor was delayed a number of times from 2023 to 2026. It, of course, gained eight additional cores in the meantime, but this hardly justifies a three-year delay.
"We have five development teams in Europe: Maisons Laffitte, Massy (both in the Paris region), Grenoble and Sofia Antipolis in France, Barcelona in Spain," Prunty said. "The Bologna team is currently being put together."
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