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 Post subject: FPU Support
PostPosted: Thu Jun 14, 2012 9:33 am 
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Joined: Thu Feb 16, 2012 4:34 pm
Posts: 17
I am not so much after the supporting of 68020/30/40-support, I do not see a big advantage in that.
But builtin FPU-support would be a big boost in the possibilities to use the Emulator (calculation, graphics).
Above all, I would expect a big impact on performance if the major functions (exp(), sine, cos etc) would be available directly.

This would provide
+ all Math-functions directly instead of having to use extra code or large tables
+ and taking advantage from directly accessing the host's FPU (PC)

In addition I guess this would not be such a big effort (as the support of 68020/30/40)

If I did not miss such a discussion - is there any chance that this could be a near-future extension?

Thanks


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 Post subject: additional thougths
PostPosted: Thu Jun 14, 2012 5:48 pm 
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Joined: Thu Feb 16, 2012 4:34 pm
Posts: 17
While exploring further the request, I came to shift it a bit:

The easiest way might be to provide Math-functions with the trap #15 mechanism.
This is less elegant than building a model where the fpu is "wired" as peripheral device (as in a real system), but it would still provide almost real performance...

Regards


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 Post subject:
PostPosted: Thu Jun 14, 2012 6:14 pm 
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Joined: Mon Dec 27, 2004 11:40 pm
Posts: 318
Probably the easiest and most immediate solution is to use the coprocessor vector to call FPU emulation code.

Lee.


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 Post subject: Re: additional thougths
PostPosted: Thu Jun 14, 2012 6:16 pm 
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Joined: Mon Jul 26, 2010 11:43 pm
Posts: 198
Location: Aurora, IL
I've discussed the 68881/2 stuff previously, it's a pretty complicated device to emulate accurately, and certainly a heck of a task to validate across all operational modes, the 80x87 could certainly assist, but they are different beasts.

You should look at IDE68K, supports 68020 and 6888x out of the box.

To emulate the co-processor, you could use the "Line 1111 Emulator" trap


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 Post subject:
PostPosted: Thu Jun 14, 2012 6:17 pm 
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Joined: Mon Jul 26, 2010 11:43 pm
Posts: 198
Location: Aurora, IL
http://www.easy68k.com/EASy68Kforum/vie ... php?t=1043


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 Post subject: some clarifications
PostPosted: Thu Jun 14, 2012 8:41 pm 
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Joined: Thu Feb 16, 2012 4:34 pm
Posts: 17
Hi there,

I really started with the idea to *emulate* the FPU. But as I found it dead slow and very inconvenient to calculate exp(x), sin(x) or the like I ended up just trying to use today's PC power by coding these functions in C and making them available through the trap #15
Ex.:
move.l <some value>,d1
move #<function number>,d0
trap #15
...receive the Math-function-result in d0 and continue processing

Although I did not have a look into the source code of Easy68k, I think this could be added rather easily.
The code would be executed by the host processor and NOT be emulated.


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 Post subject: Re: FPU Support
PostPosted: Sun Dec 30, 2012 11:54 pm 
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Joined: Thu Dec 16, 2004 6:42 pm
Posts: 1056
There are some fast floating point routines available in the examples.

It would be possible to add trap tasks to provide similar functionality.

It would also be possible to include emulation of real fpu hardware.

_________________
Prof. Kelly


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