P96 3.0.0 (and later) news and support - Page 35

klx300r · 13 May 2024, 05:41

@ Thomas

busy season for work so my testing is going alot slower nowadays but I did notice today that the horizontal bands are much better when I disable Roadshow

Thomas Richter · 13 May 2024, 07:28

That does not sound very helpful. The bars appear because the FPGA on the board is not able to prefetch the video RAM contents on time, and thus cannot draw the pixels on time: I can only guess that with RoadShow active, the Roadshow task periodically requires the Zorro bus, and somehow the FPGA needs time to analyze the Zorro cycles - time that is then missing for performing the video RAM fetch.

Anyhow, this should be solvable with the right amount of prefetch (i.e. giving the FPGA more chances to access the video RAM upfront).

Again, please remember that this is not only depending on the DAC mode (chunky, hicolor, truecolor) but also on the horizontal frame width.

klx300r · 13 May 2024, 21:07

Thanks for the explanation

I'm hoping to check every single screen mode to hunt down the perfect prefetch # for each screen mode.

Question: Do I need to reset my 4000 every time I test a different prefetch # on the same screen mode

Thomas Richter · 13 May 2024, 21:46

No, of course not. The prefetch is reset to the default value whenever you change a screen mode with intuition (or P96Prefs).

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13 May 2024, 05:41	#681
klx300r Registered User Join Date: Oct 2007 Location: ManCave, Canada Posts: 1,615	@ Thomas busy season for work so my testing is going alot slower nowadays but I did notice today that the horizontal bands are much better when I disable Roadshow

13 May 2024, 07:28	#682
Thomas Richter Registered User Join Date: Jan 2019 Location: Germany Posts: 3,247	That does not sound very helpful. The bars appear because the FPGA on the board is not able to prefetch the video RAM contents on time, and thus cannot draw the pixels on time: I can only guess that with RoadShow active, the Roadshow task periodically requires the Zorro bus, and somehow the FPGA needs time to analyze the Zorro cycles - time that is then missing for performing the video RAM fetch. Anyhow, this should be solvable with the right amount of prefetch (i.e. giving the FPGA more chances to access the video RAM upfront). Again, please remember that this is not only depending on the DAC mode (chunky, hicolor, truecolor) but also on the horizontal frame width.

13 May 2024, 21:07	#683
klx300r Registered User Join Date: Oct 2007 Location: ManCave, Canada Posts: 1,615	Thanks for the explanation I'm hoping to check every single screen mode to hunt down the perfect prefetch # for each screen mode. Question: Do I need to reset my 4000 every time I test a different prefetch # on the same screen mode

13 May 2024, 21:46	#684
Thomas Richter Registered User Join Date: Jan 2019 Location: Germany Posts: 3,247	No, of course not. The prefetch is reset to the default value whenever you change a screen mode with intuition (or P96Prefs).

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