IBM mainframe chip runs Z and Arm workloads on same cores

IBM's next-generation mainframe processor puts 11 cores on a 2-nanometer die, clocked above 5.7 GHz, and lets each core flip between IBM's Z instruction set and Arm in the nanosecond range. The chip was unveiled at the Hot Chips conference and, VentureBeat reports, is described as 'what may be the most consequential change to mainframe architecture in decades.'

The switch runs through the open-source KVM hypervisor. 'That switch takes about the nanosecond scale,' said Christian Jacobi, IBM Fellow and chief technology officer of IBM Systems Development, describing a switching overhead that 'sort of amortizes to zero.' What it buys IBM is the ability to keep decades of Z software on the same silicon as the wider Arm catalogue: 'That enables us to run the mission-critical enterprise software right next, on the same chip, to the much broader software ecosystem of Arm applications.'

Tina Tarquinio, chief product officer for IBM Z and LinuxONE, framed the motivation as a porting problem, not a customer demand. 'No matter how great our ecosystem team is, we would never be able to work with all of them and port them all,' she said. Clients weren't asking for dual-architecture, she added; they were asking IBM to 'help me get these surround workloads...to run in a quicker-to-market fashion.' Her pitch to existing shops: 'This is a big and. It is not an or.'

Alongside the cores, the chip carries a next-generation Spyre AI accelerator with high-bandwidth memory, aimed at 'ultra-low-latency inference such as fraud scoring inside a payment transaction' and 'document understanding and insurance adjudication.' The system is expected around 2028, following the three-year cadence set by z17, which shipped in Q2 2025. The article publishes no commercial name for the chip and no detailed Spyre specs.

The partnership with Arm was unveiled in April; this is its first hardware milestone. Context: IBM cut its 2026 outlook in July after Q2 mainframe revenue fell 42%, so a 2028 chip that can absorb Linux/Arm workloads without giving up Z software is a plainly defensive move.