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Welcome to SpecOS!

What is SpecOS

SpecOS is a pet project to create a multi-tasking OS for the ZX Spectrum +3 computer.

SpecOS (in a conceptual form) was born around September 1994, and came to life for real sometime around August 2010. The original idea was based on stack-switching, driven by the 50Hz ULA raster interrupt to the cpu.

After a 16-year gap, including University and 10 or so years in the computing industry working with Unix, this developed into a general-purpose Unix-style kernel-based model, striving to implement as much as possible without disabling interrupts, and therefore to reduce the amount of time lost e.g. during disk accesses (which CP/M is documented to suffer from).

Aims

• Must be runnable on real, unmodified +3 hardware with no expansion devices to "assist" or replacement ROMs (although a relatively common peripheral of the time with some RAM, like a Multiface could perhaps help out with a bit of extra RAM).
• Userland processes have no knowledge of other programs running.
• Userland processes have no knowledge of kernel implementation, load address, etc...
• Avoid disabling interrupts where possible.
• Avoid memory fragmentation.
• Must be "thread-safe" (i.e. preemptible at any point).
• Userland processes can also be compiled natively under Unix (with some helper library support).

Above all, this is a learning exercise, so there is a general policy of "don't copy code from anywhere". Yes it's re-inventing the wheel somewhat, but that's kind of the aim here!

[Where to start]
[Tools]
[Installation]
[Disk Images]

Project Members:

• Brian Ruthven (admin)