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Old 09 November 2016, 23:12   #1
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Emulated FPU precision

Last time I run Mand2000:

When I started to zoom fractal, I saw some distortion. I compared it with my Amiga, where it turned out that everything was OK. The problem arises only when emulation is enabled the FPU. When the WinUAE does not use the FPU then everything is OK.

Screenshots show what's going on.
Problems arise when zoomed in row x 44 and larger.

EDIT: I tested different settings (JIT on/off, 040/881/882 fpu, more compatible, unimplemented fpu instructions), each time the same effect.
(sorry for my english, I often use the translator)
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Last edited by michaljarz; 09 November 2016 at 23:22.
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Old 10 November 2016, 00:33   #2
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The difference between floatingpoint calculations in WinUAE and on a real Amiga with an FPU is that the FPU emulation in WinUAE is restricted to DoublePrecision (64 bit) and a real FPU can perform ExtendedPrecision (80 bit) too. This limitation is caused by the VC-compilers. VisualC can not handle ExtendedPrecision.

Last edited by PeterK; 10 November 2016 at 10:49.
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Old 10 November 2016, 10:33   #3
Toni Wilen
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Join Date: Aug 2001
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Age: 42
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It gets updated if someone writes assembly wrappers for all required FPU functions..

Multiprecision math libraries are not the answer because they are slower.
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