hi, i would like to known why fast forward works only with Threaded Video enabled.
$ lspci |grep -i vga
00:02.0 VGA compatible controller: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display (rev 0e)fast forward just removes audio and video sync and lets the core run as fast as possible. In your case, your CPU isn’t strong enough to run the core any faster than normal speed, apparently.
the CPU is an Intel J1900 with integrated video chip:
it has 4 cores of 2.42GHz, isn’t strong enough for fast forward 8 bit games? 
maybe it’s a video driver problem?
Shaders can slow it down, too, yes, but it really depends on the core you’re using. They vary wildly in their performance requirements.
i don’t use shaders. anyway, whit ALL other standalone emulators fast forward works normally, then it is a retroarch video driver problem.
as i imagined, it’s a video driver problem: if i set video_driver = “vulkan”, fast forward works without threaded video!
Unfortunately, with vulkan driver video quality is very bad (scrolling tearing), why? 
retroarch.cfg: https://paste.linux.community/view/7430555d
EDIT:
$ retroarch
INTEL-MESA: warning: Bay Trail Vulkan support is incomplete