GroovyMAME running at half speed when playing interlaced resolutions, part 2

[lixoman100]

Hello,

While doing my research I came across this thread: http://forum.arcadecontrols.com/index.php?topic=154706.0

It is from 2017 (so I did not want to necro it) but I'm running into the same issue currently and I couldn't find any info anywhere else on the Internet.

I'm currently running Linux on kernel 5.6rc3 and using the analog VGA output of a AMD Radeon R7 350 sent to a 15khz CRT TV. When running interlaced resolutions I get games running at half speed. I can "fix" this by setting vblank_mode=0, but this causes stutters even when running non-interlaced content.

The problem, as indicated from the 2017 thread, is that this AMD GPU is generating vblanks at half the interlaced refresh rate - every other frame. I haven't been able to find a kernel option or anything that could change this behavior.

That thread said "No final solution exists at this time.". Is this still the current situation? Is there no solution?

I'd appreciate any assistance.

[donluca]

As far as my knowledge goes, there is no solution to this.

Bear in mind also that there are also some games which are just straight bugged on MAME when set to interlaced mode (they can switch between 240p progressive and 480i in the service menu): when set to 480i they play at half speed, no matter what.

[Doozer]

Hello,

While doing my research I came across this thread: http://forum.arcadecontrols.com/index.php?topic=154706.0

It is from 2017 (so I did not want to necro it) but I'm running into the same issue currently and I couldn't find any info anywhere else on the Internet.

I'm currently running Linux on kernel 5.6rc3 and using the analog VGA output of a AMD Radeon R7 350 sent to a 15khz CRT TV. When running interlaced resolutions I get games running at half speed. I can "fix" this by setting vblank_mode=0, but this causes stutters even when running non-interlaced content.

The problem, as indicated from the 2017 thread, is that this AMD GPU is generating vblanks at half the interlaced refresh rate - every other frame. I haven't been able to find a kernel option or anything that could change this behavior.

That thread said "No final solution exists at this time.". Is this still the current situation? Is there no solution?

I'd appreciate any assistance.

Hi,

The 50% speed issue can be totally solved for interlaced resolution.
You have to apply a fix to the kernel (04_linux_15khz_interlaced_mode_fix.diff). You can get it from here:

https://github.com/D0023R/linux_kernel_15khz