NuKernel is amicrokernel that was developed atApple Computer during the early 1990s. It was the basis for theCoplandoperating system. It was written from scratch and designed using concepts from theMach 3.0 microkernel, with extensive additions for softreal-time scheduling to improve multimedia performance.^[1] Only one NuKernel version was released, with a Coplandalpha release.

Apple's NuKernel is not the microkernel inBeOS, nukernel.

NuKernel traces its history to the lengthy delays in theTaligent project, a joint Apple-IBM to develop a new modern kernel that could run various operating systems on top, which they referred to as "personalities". As delays in the project grew,Bill Bruffey, one of the authors of the Hierarchical File System used in theclassic Mac OS, gave up on Taligent and started writing his own microkernel designed specifically to run Mac OS on top, rather than multiple personalities.^[2]

In the aftermath of the failure of Copland, Apple began looking for other options. They initially considered usingBeOS as the basis for a future Mac operating system. The idea was to replace Be's kernel with NuKernel, and using Be'sapplication programming interfaces on top. This would allow Apple to leverage their previous work on hosting the existing Mac OS on NuKernel, instead of having to port that to Be's kernel. This would also allow them to run older Mac software, a Java virtual machine, and newPowerPC native apps built on Be.^[3]

After Apple purchasedNeXT instead of Be, at the urging ofEllen Hancock, there was still some momentum to use NuKernel as the basis for the new OS. This suggestion apparently offended Steve Jobs, and Hancock was soon demoted to research and development, into a position that was eliminated shortly after.^[4] The official death of NuKernel was on 3 February 1997 when the decision was made to move forward with the Mach kernel from NeXT.^[5]

The one-time technical lead for NuKernel,Jeff Robbin, was one of the leaders ofiTunes and theiPod.

The External Reference Specification (ERS) for NuKernel is contained in its entirety in its patent.^[6]

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