English Amiga Board - View Single Post - Huge slowdown with low-latency vsync + no buffering + interlaced screen

mark_k · 21 April 2012, 21:10

Hi,

I think I originally mentioned this issue somewhere in the 2.4.0 beta thread, but I've done some more testing and it doesn't seem to be beta-specific. The problem happens both in native Windows Vista and under Wine. In some situations there's a huge slowdown (mouse pointer jumps, only moving once or twice each second). As far as I can tell, it happens when:

Low-latency vsync is used, and
No buffering, and
CPU emulation speed is set to Fastest possible, and
Emulated Amiga video output is interlaced

It happens with both none and Null filter, Direct3D and DirectDraw, sound enabled or not, JIT and non-JIT. To hopefully reproduce the problem:

Boot a Workbench disk. Set screenmode to PAL:High Res Laced.
Run a program which opens a non-interlaced screen, e.g. SysInfo.
Press F12, enable low-latency vsync and select No buffering. Everything should be working fine at this point.
If you're using Kickstart 2.0+, hold left Amiga and drag the pointer down to move the SysInfo screen down. When part of the Workbench is revealed, the Amiga output becomes interlaced and you should notice the slowdown. (If using Kickstart 1.x instead press left Amiga-N to bring Workbench to front and see slowdown. You can drag WB screen down to reveal SysInfo screen.)
If you drag the SysInfo screen back up (so the video output is non-interlaced again) the slowdown vanishes.

I'm using the Nvidia driver, both in Windows and Linux. Geforce Go 7300 chip, 2.1GHz Core 2 Duo T8100 CPU.

Edit: Problem seems to only happen when CPU emulation speed is fastest possible.

21 April 2012, 21:10	#1
mark_k Registered User Join Date: Aug 2004 Location: Posts: 3,344	Huge slowdown with low-latency vsync + no buffering + interlaced screen Hi, I think I originally mentioned this issue somewhere in the 2.4.0 beta thread, but I've done some more testing and it doesn't seem to be beta-specific. The problem happens both in native Windows Vista and under Wine. In some situations there's a huge slowdown (mouse pointer jumps, only moving once or twice each second). As far as I can tell, it happens when: Low-latency vsync is used, and No buffering, and CPU emulation speed is set to Fastest possible, and Emulated Amiga video output is interlaced It happens with both none and Null filter, Direct3D and DirectDraw, sound enabled or not, JIT and non-JIT. To hopefully reproduce the problem: Boot a Workbench disk. Set screenmode to PAL:High Res Laced. Run a program which opens a non-interlaced screen, e.g. SysInfo. Press F12, enable low-latency vsync and select No buffering. Everything should be working fine at this point. If you're using Kickstart 2.0+, hold left Amiga and drag the pointer down to move the SysInfo screen down. When part of the Workbench is revealed, the Amiga output becomes interlaced and you should notice the slowdown. (If using Kickstart 1.x instead press left Amiga-N to bring Workbench to front and see slowdown. You can drag WB screen down to reveal SysInfo screen.) If you drag the SysInfo screen back up (so the video output is non-interlaced again) the slowdown vanishes. I'm using the Nvidia driver, both in Windows and Linux. Geforce Go 7300 chip, 2.1GHz Core 2 Duo T8100 CPU. Edit: Problem seems to only happen when CPU emulation speed is fastest possible. Last edited by mark_k; 22 April 2012 at 11:02.