(Image credit: Intel)

Intel has patented a technology it calls 'Software Defined Supercore' (SDC) that enables software to fuse the capabilities of multiple cores to assemble a virtual ultra-wide 'supercore' capable of improving single-thread performance, provided that it has enough parallel work. If the technology works as it is designed to, then Intel's future CPUs could offer an single-thread performance in select applications that can use SDC. For now this is just a patent which may, or may not become a reality.

Intel's Software Defined Supercore (SDC) technologies combine two or more physical CPU cores to cooperate as a single high-performance virtual core by dividing a single thread's instructions into separate blocks and executing them in parallel. Each core runs a distinct portion of the program, while specialized sync and data-transfer instructions ensure the original program order is preserved to maximize instructions per clock (IPC) with minimal overhead. This approach is designed to improve single-thread performance without increasing clock speeds or building wide monolithic cores, which increases power consumption and/or transistor budgets.

Modern x86 CPU cores can decode 4 – 6 instructions and then execute 8 - 9 micro-ops per cycle after instructions are decoded into micro-ops, which is peak IPC performance for such processors. By contrast, Apple's custom Arm-based high-performance cores (e.g., Firestorm, Avalanche, Everest) can decode up to 8 instructions per cycle and then execute over 10 instructions per cycle under ideal conditions, which is why Apple's processors typically offer significantly higher single-threaded performance and at lower power compared to Arm counterparts.

While it is technically possible to build an 8-way x86 CPU core (i.e., a superscalar x86 processor that can decode, issue, and retire up to 8 instructions per clock), but in practice, it has not been done because of front-end bottlenecks as well as diminishing returns in terms of performance increase amid significant, power and area costs. In fact, even modern x86 CPUs can typically hit 2–3-4 sustained IPC on general workloads, depending on software. So, instead of building an 8-way x86 CPU core, Intel's SDC proposes to pair two or more 4-wide units to cooperate as one huge core in cases when it makes sense.

On the hardware side of matters, each core in an SDC-enabled system includes a small dedicated hardware module that manages synchronization, register transfers, and memory ordering between paired cores. These modules use a reserved memory region — called the wormhole address space — for coordinating live-in/live-out data and sync operations to ensure that instructions from separate cores retire in the correct program order. The design supports in-order and out-of-order cores, and requires minimal changes to the existing execution engine, which means it is tiny in terms of die space that it takes.

On the software side, the system uses either a JIT compiler, static compiler, or binary instrumentation to split a single-threaded program into code segments to assign different blocks to different cores. It injects special instructions for flow control, register passing, and sync behavior, enabling the hardware to maintain execution integrity. Support by operating system is crucial as the OS dynamically decides when to migrate a thread into or out of super-core mode based on runtime conditions to balance performance and core availability.

Intel's patent does not provide exact numerical performance gain estimates, but it implies that in select scenarios it is realistic to expect performance of two 'narrow' cores to approach performance of a 'wide' core.

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