6888x cores

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bhamadicharef
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6888x cores

Post by bhamadicharef »

Any interest or need to implement the Motorola 6888x floating point coprocessor ?
If I remember well they worked with the TRAP instruction with sequence of passing
values and waiting for results ...

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Re: 6888x cores

Post by Newsdee »

are you volunteering? :D
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Re: 6888x cores

Post by ex68k »

bhamadicharef wrote:Any interest or need to implement the Motorola 6888x floating point coprocessor ?
Brahim @ Singapore
Just go for it, an complete working 68882 would be nice ;-)
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Re: 6888x cores

Post by Sorgelig »

Yeah, why not?
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Re: 6888x cores

Post by Grabulosaure »

I've already made a single & double precision IEEE FPU... Good luck!

If you get the basic operations in hardware (+-*/, conversions), the one available on 68040, you could try to turn the Motorola emulation library for the 040 into microcode for a complete 68882 FPU.
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Re: 6888x cores

Post by JimDrew »

You might want to consider the 040 internal version of the FPU, which is simplified. I have test code for 881/882/040/060 FPUs that I can run if someone is going to create FPU support.
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Re: 6888x cores

Post by ThorstenOtto »

bhamadicharef wrote:Any interest or need to implement the Motorola 6888x floating point coprocessor ?
If I remember well they worked with the TRAP instruction with sequence of passing
values and waiting for results ...
Its using so-called Line-F instructions (all opcodes concerning a coprocessor start with hex F, and there can be multiple of them, like a PMMU and a FPU). And IIRC, at least some of the functions can be executed in parallel to the CPU.
you could try to turn the Motorola emulation library for the 040 into microcode for a complete 68882 FPU.
I don't think that this will help much, it is only emulating the missing functions.
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Re: 6888x cores

Post by bhamadicharef »

JimDrew wrote:You might want to consider the 040 internal version of the FPU, which is simplified. I have test code for 881/882/040/060 FPUs that I can run if someone is going to create FPU support.
Please share these test codes, thanks. Wonder if MAME has 6888x already.

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Re: 6888x cores

Post by JimDrew »

bhamadicharef wrote:Wonder if MAME has 6888x already.
Yes, along with 68882 test code as well - just like WinUAE/FS-UAE does.
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Re: 6888x cores

Post by Grabulosaure »

For validating the core arithmetic operations, the IEEEcc754 library (http://elpub.bib.uni-wuppertal.de/servl ... et?id=7690)
was very useful. It can generate tests patterns with all the tricky combinations of rounding, denormals, overflows, ...

Here is, for example, a set of 30000+ vectors for single and double IEEE.
They can be completed with random tests from a reference implementation.
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bhamadicharef
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Re: 6888x cores

Post by bhamadicharef »

thanks you Leslie from U.K. for sending me a MC68881 for free. Will build a testing shield for
Arduino, bigger Mega probably needed, to have “digital twin” for tests ... will update when
starting progress on this.
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