VIFCMD 12
Description
Checks the behaviour of an undefined VIF command (0x12)
This command is intriguing because it's CMD byte happens to be sandwiched between defined VIF FLUSH[X] CMD bytes
FLUSHE -> 0x10
FLUSH -> 0x11
??? -> 0x12
FLUSHA -> 0x13
The procedure for checking this behaviour is to upload a micro program to VU1 that loops indefinitely. Then see if the VIF will wait for the micro programs end.
PCSX2 Behaviour
When coming across this command, PCSX2 will set ER1 in VIFSTAT and emit the following message:
Vif1: Unknown VifCmd! [12]
This would happen to be the correct behaviour.
Findings
When the VIF executes an instruction with CMD 0x12, it will not wait for an E bit (end of micro program).
ER1 in VIFSTAT will be set.
Related PR(s) or Issue(s)
https://github.com/PCSX2/pcsx2/issues/4179
Expected Results
(VIF1STAT ER1 = 2000 -> ER1 bit is set)
VIF1STAT ER1 = 0
VIF1 finished, VIF1STAT ER1 = 2000
In the case that you replace the 0x12 CMD with a proper FLUSH command, the result would be expected to be:
VIF1STAT ER1 = 0
waited 10 mil times (VIF1STAT ER1 = 0)
waited 20 mil times (VIF1STAT ER1 = 0)
waited 30 mil times (VIF1STAT ER1 = 0)
waited 40 mil times (VIF1STAT ER1 = 0)
...
In this case, we are waiting on the VIF to finish waiting on the micro program, which will complete during your next power outage. :^)