3 ms·

I wonder how they will tackle the infamous non-conformant Ps2 floating-point behavior issue, that is the biggest hurdle on emulating Ps2.

mikepurvis 9mo ago
Some context for others who were unaware: https://github.com/PSI-Rockin/DobieStation/issues/51 https://github.com/PSI-Rockin/DobieStation/issues/51 EDIT here's potentially a better link: https://www.gregorygaines.com/blog/emulating-ps2-floating-point-nums-ieee-754-diffs-part-1/ https://www.gregorygaines.com/blog/emulating-ps2-floating-po...
kmeisthax 9mo ago
PS2 floating-point behavior is one of the few hardware misfeatures so awful it affects emulation of competing systems[0]. The game True Crime: New York City is so dependent on PS2 floating point that the GameCube port installs an error handler just to make 1/0 = 0. Which isn't even PS2 hardware behavior. But it is "close enough" that the game does not immediately throw you into the void every time you step on a physics object. [0] https://dolphin-emu.org/blog/2021/11/13/dolphin-progress-report-september-and-october-2021/#50-15330-raise-program-exceptions-on-floating-point-exceptions-by-josjuice https://dolphin-emu.org/blog/2021/11/13/dolphin-progress-rep...
realusername 9mo ago
Probably the same way as the emulator themselves, with a list of titles needing the real PS2 floating point. A lot of titles don't actually need it and work fine with standard IEEE floating point.
toast0 9mo ago
As of now, it looks like they're ignoring it: https://github.com/ran-j/PS2Recomp/blob/91678d19778891b4df854af0a2e9d5c162fb42c1/ps2xRuntime/output/ps2_runtime_macros.h#L133 https://github.com/ran-j/PS2Recomp/blob/91678d19778891b4df85... #define FPU_ADD_S(a, b) ((float)(a) + (float)(b)) (etc) But if you wanted to handle it, you'd presumably macro expand the floating point operations to something that matches the PS2 fpu (or comes closer).
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mikepurvis 9mo ago

Some context for others who were unaware: https://github.com/PSI-Rockin/DobieStation/issues/51 https://github.com/PSI-Rockin/DobieStation/issues/51 EDIT here's potentially a better link: https://www.gregorygaines.com/blog/emulating-ps2-floating-point-nums-ieee-754-diffs-part-1/ https://www.gregorygaines.com/blog/emulating-ps2-floating-po...

kmeisthax 9mo ago

PS2 floating-point behavior is one of the few hardware misfeatures so awful it affects emulation of competing systems[0]. The game True Crime: New York City is so dependent on PS2 floating point that the GameCube port installs an error handler just to make 1/0 = 0. Which isn't even PS2 hardware behavior. But it is "close enough" that the game does not immediately throw you into the void every time you step on a physics object. [0] https://dolphin-emu.org/blog/2021/11/13/dolphin-progress-report-september-and-october-2021/#50-15330-raise-program-exceptions-on-floating-point-exceptions-by-josjuice https://dolphin-emu.org/blog/2021/11/13/dolphin-progress-rep...

realusername 9mo ago

Probably the same way as the emulator themselves, with a list of titles needing the real PS2 floating point. A lot of titles don't actually need it and work fine with standard IEEE floating point.

toast0 9mo ago

As of now, it looks like they're ignoring it: https://github.com/ran-j/PS2Recomp/blob/91678d19778891b4df854af0a2e9d5c162fb42c1/ps2xRuntime/output/ps2_runtime_macros.h#L133 https://github.com/ran-j/PS2Recomp/blob/91678d19778891b4df85... #define FPU_ADD_S(a, b) ((float)(a) + (float)(b)) (etc) But if you wanted to handle it, you'd presumably macro expand the floating point operations to something that matches the PS2 fpu (or comes closer).

deleted 9mo ago

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