Yes, literally not correct answer, but, a little common sense, who uses FB Alpha CPS1? if nobody knows mame 2003+, which is relatively important. Flycast and Kronos are not even listed as Arcade cores.
I was very naive to assume, that since MAME current and 2003+, supported input delay reduction, so would SAME and the other MAME cores, but it is not aśi fact, 2003+ does not support it.
It is undoubtedly wrong.
Run-Ahead with dual instances operate at about the same speed as Preemptive Frames, which handles a single instance. 3%/5% less.
When only one instance is activated, it runs at half the speed. FBNeo is slightly faster than MAME.
To complement the answer, with Preemptive frames (or Run-Ahead) FBNeo is the best option because it has better support, but if you want to play (FOR EXAMPLE) Killer Instinc, MAME Current is the only one that supports latency reduction, considering it is not optimized and the support that MAME has in RetroArch is pitiful.
Now, the important thing about the question, is the question.
@febs f you give more detailed information, you can get to a solution faster. It’s hard to guess.
What operating system? what cores are giving you the problem? vulkan?
Because if you are using MAME Current or FBNeo, your problem is a misconfiguration.