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Projects: Extending Machine Instructions

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Project history
The design ideas arose in the Eighties. The starting point was the task to develop a successor to a Z80-based multiprocessor system. Existing software had to be retained. So a transition to one of the then-contemporary 16-bit microprocessors was not feasible. A more detailed analysis had shown that only a few functions had to be accelerated. Extending the basic Z80 system by a control storage instead of designing a microprogrammed accelerator was a spontaneous idea.

License conditions
The technical solutions communicated here can be used freely (open-source hardware / open-source software). The terms of the CERN Open Hardware License Version 2 – Permissive apply. Functionality, suitability for any purpose, and freedom from other property rights cannot be guaranteed. The license terms – together with more detailed explanations – can be found at the following Internet addresses:

https://www.ohwr.org/project/cernohl/wikis/home

https://www.ohwr.org/project/cernohl/wikis/Documents/CERN-OHL-version-2

https://ohwr.org/cern_ohl_p_v2.pdf

For the curious
These excerpts of marketing pics from the past show two machines in which some of the described design ideas have been implemented. In my private nomenclature, the machine to the left is the system .004, the machine to the right is the system .011, the latter containing most of the circuits described in [4] to [8] and in the synopsis.