Every few years someone realizes that many small CPUs on a chip have many times the peak performance of a single small CPU. Unfortunately for the companies that pursue this idea, this approach is rarely (if ever) better than fewer, more powerful cores or specialized engines. Nonetheless, Inspire Semiconductor continues down this extreme-multicore path and has recently announced it has taped out its Thunderbird processor that integrates 1,536 RISC-V cores.
Thunderbird is the company’s second or third such chip. Cryptocurrency miner CryptoCore employed Gen1 and signed up to use InspireSemi’s creatively named Gen2, as did EdgeMode, another miner. It’s unclear whether Gen2 entered production or even taped out. Like Thunderbird, it connected a thousand-plus 64-bit RISC-V cores with a mesh fabric.
InspireSemi Is Already Publicly Traded
CryptoCore developed Gen1 and in 2020 spun out its chip team as InspireSemi, at which time it began talking up Gen2. The next year it announced its first two customers, as noted above. In 2022, Greenfield Acquisition merged with InspireSemi. Greenfield was a capital pool company, the Canadian equivalent of a special-purpose acquisition company (SPAC). InspireSemi shares now trade on the TSX-V exchange (ticker: INSP.V). In 2023, it recognized $75,000 in sales related to early-access customers, up from revenue of $9,000 the prior year. In 1Q24, it scored another $55,000. On the back of this positive revenue trend and the announced tape out, the company’s stock price has climbed to nearly 20 cents, almost surpassing its 12-month high.
Thunderbird Is a RISC-V Processor
Fabricated in a TSMC 12 nm process, the approximately 450 mm2 InspireSemi Thunderbird can scale out beyond the chip boundary. The company states 256 Thunderbirds can connect, and its PCIe add-in card features four chips. Thunderbird’s CPUs are a proprietary 64-bit RISC-V out-of-order, superscalar design with cryptography and networking (but not AI or vector) extensions. Each CPU has a small 64 KB local memory. The processor also has six DDR4 memory controllers, 128 PCIe Gen 4 lanes, and unspecified accelerators. The company estimates each Thunderbird requires 150 W and has suggested a two-chip PCIe card would list for $6,500. InspireSemi plans a 4 nm follow on, which could integrate more cores, deliver greater throughput per watt, or reduce die size.
Bottom Line
Although small, InspireSemi’s revenue indicates at least one customer is interested in Thunderbird. Unfortunately, simply integrating many cores on a chip hasn’t proven to be a successful strategy to appeal to more than a few niche customers. Having taped out the new processor, InspireSemi will require a few quarters to elapse before revenue can ramp up and prove the company to be an unexpected success.