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===VU1 emulation on SPE===
===VU1 emulation on SPE===
VU1 SPE program starts at 0x4000 of LS. Start function is responsible for loading all 128 spe registers with values from memory starting from 0x4230 of LS for r0, ends at 0x4A20 for r127 (r127 is trashed literally in next opcode after that...). This should result in all 0 value regs, excluding r0 which will be set to float(1.0, 0, 0, 0) like ps2 vf00. After that function notify PPE side that its done, and jump to 0x8000, here fun begins. SPE program now clear LS memory from 0x0000 to 0x7FF0, this include VU1 data mem that is located at first 0x4000 bytes. What's more important function that we started at 0x4000 will be deleted. Yup, self modifying code on SPU (good luck for eventual emulator that will try to run ps2_netemu).
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When I disassembled VU1 SPE program, i noticed that real code is really small part of that. Not much to run real VU recompiler/interpreter.
When I disassembled VU1 SPE program, i noticed that real code is really small part of that. Not much to run real VU recompiler/interpreter.
Then i found out something impressive in my opinion. Real deal is that real code delivered to SPE is created on PPE dynamically based on real PS2 VU1 code. Due to similarity of SPE with VU requested in IBM by Sony at design level, there is no VU1 interpreter or recompiler per se. Emulator take VU1 code, dismount it to parts by OP field types, and reassemble into ready SPE code using ready hex templates. I'm not familiar with professional naming of that operation, but its like ahead of time translation of code. So when VU1 code reach SPE is already translated to SPE opcodes. In other terms, SPE responsible for running VU1 is really running VU1 code in some way.
Then i found out something impressive in my opinion. Real deal is that real code delivered to SPE is created on PPE dynamically based on real PS2 VU1 code. Due to similarity of SPE with VU requested in IBM by Sony at design level, there is no VU1 interpreter or recompiler per se. Emulator take VU1 code, dismount it to parts by OP field types, and reassemble into ready SPE code using ready hex templates. I'm not familiar with professional naming of that operation, but its like ahead of time translation of code. So when VU1 code reach SPE is already translated to SPE opcodes. In other terms, SPE responsible for running VU1 is really running VU1 code in some way.
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