Editing PS2 Emulation

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==Description==
==Description==
[[File:Ps2_block_diagram.png|200px|thumb|right|Simplified block diagram of a PS2<br />[http://www.philvaz.com/games/PS2.htm source]]]
Emulation of Playstation 2 is currently handled by 3 kind of emulators. CECH-A/B models use ps2_emu.self able to use built-in PS2 hardware (EE/GS/Rambus memory), and have best compatibility. CECH-C/E use ps2_gxemu, this emulator use physical Graphic Synthesizer found in this ps3 model, but Emotion Engine is fully emulated here, also there is no Rambus memory. All other models emulate PS2 thru fully software based ps2_netemu used for ps2 classics, and hacked now to use decrypted ISO files. Earlier before Sony provided ps2 classics on PS Store there was another soft only emulator strongly based on ps2_gxemu. It was called ps2_softemu, and had support for original PS2 CDVD. Only emulator not able to run physical discs is ps2_netemu.  
Emulation of Playstation 2 is currently handled by 3 kind of emulators. CECH-A/B models use ps2_emu.self able to use built-in PS2 hardware (EE/GS/Rambus memory), and have best compatibility. CECH-C/E use ps2_gxemu, this emulator use physical Graphic Synthesizer found in this ps3 model, but Emotion Engine is fully emulated here, also there is no Rambus memory. All other models emulate PS2 thru fully software based ps2_netemu used for ps2 classics, and hacked now to use decrypted ISO files. Earlier before Sony provided ps2 classics on PS Store there was another soft only emulator strongly based on ps2_gxemu. It was called ps2_softemu, and had support for original PS2 CDVD. Only emulator not able to run physical discs is ps2_netemu.  


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PS3 models without Emotion Engine unit use "SPE-compatible SIMD graphics-rounding mode for VMX/Altivec Instructions" for FPU, and VU0 emulated floats calculations. This is set on emulator init by HV call 97 with param 1. VU1 actually run at SPE core so no compatibility mode need (or can) to be set. SPE compatible mode for PPE mean that rounding mode is set as round to zero, denormals are treated as zero, and there are no infinities or NaNs. So theoretically what PS2 FPU/VU was originally. Although SPE and PPE SPE compatibility mode is still inaccurate comparing to PS2, because Sony decided to cut off 2 guard bits from calculations on PS2. Probably because there was no need for round and sticky bits (no Nan/Inf, one round mode, etc.). Additionally float divide algorithm is custom and not fully understood up to this day. Good example here are TriAce games, or Castlevania COD where SPE calculation is wrong by 1 bit making games unplayable without patch. This are PS2 math algo specific inaccuracies in FPU/VU implementation that are not present on any other hardware.
PS3 models without Emotion Engine unit use "SPE-compatible SIMD graphics-rounding mode for VMX/Altivec Instructions" for FPU, and VU0 emulated floats calculations. This is set on emulator init by HV call 97 with param 1. VU1 actually run at SPE core so no compatibility mode need (or can) to be set. SPE compatible mode for PPE mean that rounding mode is set as round to zero, denormals are treated as zero, and there are no infinities or NaNs. So theoretically what PS2 FPU/VU was originally. Although SPE and PPE SPE compatibility mode is still inaccurate comparing to PS2, because Sony decided to cut off 2 guard bits from calculations on PS2. Probably because there was no need for round and sticky bits (no Nan/Inf, one round mode, etc.). Additionally float divide algorithm is custom and not fully understood up to this day. Good example here are TriAce games, or Castlevania COD where SPE calculation is wrong by 1 bit making games unplayable without patch. This are PS2 math algo specific inaccuracies in FPU/VU implementation that are not present on any other hardware.


[[File:Ps2_block_diagram.png|200px|thumb|right|Simplified block diagram of a PS2<br />[http://www.philvaz.com/games/PS2.htm source]]]
Note:  
Note:  
* not available in early Tool/DECR and Debug/DEX firmwares. But available in AV TOOL firmware since 1.00
* not available in early Tool/DECR and Debug/DEX firmwares. But available in AV TOOL firmware since 1.00
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