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[GTE] More info about load delay slots

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wheremyfoodat 2022-08-23 00:09:57 +03:00
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7
docs/geometrytransformationenginegte.md
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@ -14,7 +14,7 @@
#### GTE Operation
The GTE doesn't have any memory or I/O ports mapped to the CPU memory bus,
instead, it's solely accessed via coprocessor opcodes:<br/>
```
```x86asm
mov cop0r12,rt ;-enable/disable COP2 (GTE) via COP0 status register
mov cop2r0-63,rt ;\write parameters to GTE registers
mov cop2r0-31,[rs+imm] ;/
@ -24,6 +24,11 @@ instead, it's solely accessed via coprocessor opcodes:<br/>
jt cop2flg,dest ;-jump never ;\implemented (no exception), but,
jf cop2flg,dest ;-jump always ;/flag seems to be always "false"
```
#### GTE Load Delay Slots
Using CFC2/MCF2 has a delay of 1 instruction until the GPR is loaded with its new value.
Certain games are sensitive to this, with the notable example of Tekken 2
which will be filled with broken geometry on emulators which don't emulate this properly.<br/>
GTE (memory-?) load and store instructions have a delay of 2 instructions, for
any GTE commands or operations accessing that register. Any? That's wrong!<br/>
GTE instructions and functions should not be used in<br/>