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i was using the vu0 in macromode only so far and would like to use vcallms for some algorithms where i just move some values directly into vu0-registers (using the lqc2 instruction) and then start a subroutine from vu0-micromem. after the subroutine is finished i would store the value with sqc2 in main memory.

i saw an example that looked like this:

lqc2 vf4,0x0(%0)
lqc2 vf5,0x0(%1)
vcallms %2
sqc2 vf4, 0x0(%0)

since there is no code that waits for the end of the subroutine,
does that mean the vcallms-instruction is waiting until the subroutine is finished or does the following sqc2-instruction stall until its finished?

2nd would be better since i could do something else in the meantime.


thanks for any help

The only opcodes that does any interlocking with vu0 is qmfc2 and qmtc2, so they are the only ones actually waiting for a microprogram to finish after vcallms/vcallmsr,
lqc2 and sqc2 doesnt do any interlocking so they will just load/store the values at the time of execution. if you want to do stuff in the meantime of a mpg check the status register for vu0 when you want to fetch the result.

thanks blackdroid

so if qmfc2 interlocks with vu0 then i dont need a loop where i read the status register and check if vu0 is still running, one qmfc2 instruction would suffice before writing the rest to memory?

for example:

i should have said qmtc2.i/qmfc2.i, the normal operation is without interlock.
but yes your way of thinking is correct, just change qmfc2 to qmfc2.i

ok, thanks a lot.

Is this some kind of a bot? Can someone ban him and delete his nonsense posts?

You may want to see this earlier VU topic thread which discusses the issue of interlock:

http://forums.ps2dev.org/viewtopic.php?t=494