Problem with Run Ahead

RetroArch General
#1

Hi there,

I like to play Kaizo Mario Rom Hacks which require very precice inputs and movement.

I LOVE retroarch’s run-ahead feature. Using 2 frames of run-ahead makes it Basically 100% equal to actual hardware. It’s amazing!

However, sometimes if I used other programs before or while usinr retroarch, the run-ahead becomes inconsistent. Sometimes it happens, sometimes it doesn’t. Restarting retroarch 2-3 times helps in most cases.

It’s not that bad, however I wanted to stream with OBS and it basically always has a impact on run-ahead (feels like it’s turned off sometimes. restarting helps, but mostly for a short time only)

I’ve tried different video settings (including drivers) and tried different cores (snes9x 2010, snes9x current and bsnes). The problem stays the same. The only thing that really makes a different input-delay wise is the frames of run-ahead (which is 2 for me). I don’t notice much difference when changing the poll-behaviour and hard gpu sync.

Do you guys think this might be more of a CPU, GPU or maybe RAM Problem? I know run ahead hits on the CPU so would a stronger CPU maybe make a difference? If I run the task manager my cpu usage (GPU and ram too) ist still pretty low, even with obs and retroarch running.

#2

Pretty sure the real game also has 2 frames of lag.

#3

Yes, real hardware has lag too (game dependent more or less), that’s why I don’t use Latency Reduction, when the emulation matches real hardware latency already. Brunni’s famous latency investigation thread links to someone else’s Google spreadsheet Super Mario World Input Lag : Results with at least 2 frames of lag on real US hardware.

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#4

I think It does have 2 frames on real hardware but when emulating we also need to think about the whole chain, so in my case shaving frames with run-ahead will result in something between 1 and 2 (leaning on 2) frames of real delay (button press to screen animation start) roughly checked by recording a video of both monitor and button press. Some other system may have more and other can have less.

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#5

Okey, that’s cool and all, but can anyone help me with the actual problem? The incosistency?

I was thinking about buying a stronger PC with higher CPU and RAM. Would that even help, and if, is it better to focus on single core cpu (like intel) or more cpu cores (like amd)?

#6

Hard to say how much it would improve, as we don’t know your exact settings and hardware. Generally speaking for Snes emulation you basically focus on single CPU core only, as it is light on GPU and RAM usage. More cores doesn’t affect much the emulation itself, as the original hardware wasn’t multicore. While the focus should be on single core, having multiple cores and threads doesn’t hurt, especially if you want to run other programs in the background too. RAM on modern PCs is never an issue for emulation (at least to my knowledge).

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#7

What are you talking about?

What CPU, RAM, graphics card, display and OS do you have now?

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#8

Could you please be more explicit about the meaning of "inconsistent’ in that context ?

Runahead either works or doesn’t (i.e. visuals/audio/gameplay are broken), if it doesn’t then having a better cpu wouldn’t solve anything.

If you simply mean that your pc is not powerful enough to run snes with 2 frames of runahead, then your spelling is extremely confusing, and yeah in that case having a better cpu would help.