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Re: BBC Video WIP [Re: Pernod] #113213
04/24/18 05:10 PM
04/24/18 05:10 PM
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Duke Online content
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Doing your own is a solution of course, but I would love to see some generic improvements to the 6845 so that all drivers benefit.

Re: BBC Video WIP [Re: Pernod] #113214
04/24/18 05:52 PM
04/24/18 05:52 PM
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R. Belmont Offline
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I'm going to put that harder: fix the 6845 to work. Abandoning it is both cowardice and poor documentation value, and I will not look kindly upon any change lists that do so.

Re: BBC Video WIP [Re: Pernod] #113215
04/24/18 06:30 PM
04/24/18 06:30 PM
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Pernod Offline OP
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I'm not saying there's anything wrong with the current 6845, the real device doesn't output the video yet we have MC6845_UPDATE_ROW to do just that. The BBC has a VideoULA to output video RGB which takes the various 6845 outputs MA, RA, CURSOR, DE to generate video for the whole screen, not just the last area the 6845 was configured for. The amstrad driver uses the 6845 in a similar way and doesn't use MC6845_UPDATE_ROW, is that wrong?

I need to do some more testing but will probably submit current progress with borders and fixed blanking using MC6845_UPDATE_ROW. I'm not expecting this to break anything (apart from artwork) and will certainly improve many games that simply reduce the screen size to save video RAM.


BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, etc.
Re: BBC Video WIP [Re: Pernod] #113217
04/24/18 10:02 PM
04/24/18 10:02 PM
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ICEknight Offline
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Originally Posted by Pernod
The amstrad driver uses the 6845 in a similar way and doesn't use MC6845_UPDATE_ROW, is that wrong?

Could it be related to this display bug in the CPC driver? -> http://mametesters.org/view.php?id=6864


LCD artwork cleanups: https://mega.nz/#F!uFYSzK7S!U-lJon9jsqyoCX_3y7_KLA
Re: BBC Video WIP [Re: ICEknight] #113218
04/24/18 10:21 PM
04/24/18 10:21 PM
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mahlemiut Offline
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Originally Posted by ICEknight
Could it be related to this display bug in the CPC driver? -> http://mametesters.org/view.php?id=6864

I think that's related more to setting up for differing frame rates, where the driver just bases the frame rate on a machine config setting.


- Barry Rodewald
Re: BBC Video WIP [Re: R. Belmont] #113229
04/25/18 03:18 PM
04/25/18 03:18 PM
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Pernod Offline OP
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Originally Posted by R. Belmont
I'm going to put that harder: fix the 6845 to work.

If this is referring to improving mc6845_device::screen_update then I agree.

Out of curiosity, why would Machine Information report different Video resolutions depending on whether MCFG_MC6845_SHOW_BORDER_AREA is true or false?
false:
[Linked Image]
true:
[Linked Image]


BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, etc.
Re: BBC Video WIP [Re: Pernod] #113230
04/25/18 04:08 PM
04/25/18 04:08 PM
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Haze Offline
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because it shows the current visible area size, which is obviously different if borders are showing..

Re: BBC Video WIP [Re: Haze] #113614
06/27/18 04:22 PM
06/27/18 04:22 PM
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Pernod Offline OP
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Originally Posted by Haze
because it shows the current visible area size, which is obviously different if borders are showing..

Obviously, was a case of typing before thought.

Do any other drivers handle changing of the pixel clock during a scanline? This will be required to handle split modes vertically rather than the more commonly used horizontally split.

So the 6845 currently has a scanline_timer but I really need a pixel_timer. Would it makes sense to implement this in my MC6845_UPDATE_ROW or would a new MC6845_UPDATE_PIXEL be the way to go?

Again just thinking out loud for guidance.


BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, etc.
Re: BBC Video WIP [Re: Pernod] #113616
06/27/18 10:53 PM
06/27/18 10:53 PM
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Vas Crabb Online content
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MAME doesn't really support "horizontal partial updates" at the moment, and it definitely doesn't support changing resolution within a line. If you've got horizontal resolution changes within a line, you need to render at lowest common multiple. A per-pixel timer would kill performance. If you need to render per-pixel, you'd be better off making the video chip implement device_execute_interface and letting the scheduler deal with it.

Re: BBC Video WIP [Re: Pernod] #113617
06/28/18 12:37 AM
06/28/18 12:37 AM
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R. Belmont Offline
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Yeah, I need to get back to the horizontal partial update thing after my current large project lands. Gotta get those French Touch demos perfect.

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