English Amiga Board - View Single Post - Shouldn't softfloat FPU mode compatibility be 100%?

Toni Wilen · 02 November 2019, 09:55

Works for me. "HMM: 3" is result (68040 + softfloat + unimplemented unticked, 46.3 68040.library).

Code executes FLOGN (log) and FETOX (power) instructions. Softfloat uses emulation logic based on Motorola FPSP (68040+ FPU emulation library) for these instructions which should guarantee identical results. Real 68888x may or may not return slightly differrent result. (I can test this later).

Check that you get few "FPU IMPLEMENTED INSTRUCTION/FPU DISABLED EXCEPTION" log lines when you run the code. This means "hardware" FPU didn't implement it and it was trapped and emulated by FPSP.

EDIT: Also same result with unimplemented ticked.

EDIT2: 3 also in 80-bit host mode. Only 64-bit host returns wrong answer (2.9999999999999991)

02 November 2019, 09:55	#4
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,534	Works for me. "HMM: 3" is result (68040 + softfloat + unimplemented unticked, 46.3 68040.library). Code executes FLOGN (log) and FETOX (power) instructions. Softfloat uses emulation logic based on Motorola FPSP (68040+ FPU emulation library) for these instructions which should guarantee identical results. Real 68888x may or may not return slightly differrent result. (I can test this later). Check that you get few "FPU IMPLEMENTED INSTRUCTION/FPU DISABLED EXCEPTION" log lines when you run the code. This means "hardware" FPU didn't implement it and it was trapped and emulated by FPSP. EDIT: Also same result with unimplemented ticked. EDIT2: 3 also in 80-bit host mode. Only 64-bit host returns wrong answer (2.9999999999999991) Last edited by Toni Wilen; 02 November 2019 at 10:15.