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Old 05 December 2017, 16:19   #1
Seiya
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68000 6888x

is it possible to add a 68881 to a 68000 cpu model?
i found some old A500 68000 software that include 68881 codes..so in the past there was some board with 68000+68881
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Old 05 December 2017, 17:50   #2
Toni Wilen
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Moved. Totally offtopic in beta thread.
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Old 05 December 2017, 18:19   #3
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ok, sorry
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Old 05 December 2017, 18:28   #4
Toni Wilen
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68000 + 6888x is horrible hack: Code that wants to use FPU needs to simulate 68020 co-processor protocol by writing internal opcodes and parameters to IO mapped space, then wait for the FPU to execute it and then read the response back and send more opcodes until instruction is complete..

Emulating 68020 co-proc protocol is quite low level and would be really annoying to emulate.
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Old 05 December 2017, 19:59   #5
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The math libraries on Workbench 1.3 support 6888x peripheral access. If anyone's interested, probably all expansions which add 68881 with 68000 CPU implement the scheme covered in Motorola application note AN947. One such is the multi-function module for the Microbotics Starboard 2.
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Old 05 December 2017, 21:50   #6
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ah ok, thanks.
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