English Amiga Board


Go Back   English Amiga Board > Coders > Coders. General

 
 
Thread Tools
Old 19 September 2008, 14:06   #1
ovale
 
Posts: n/a
256x256 pixel tweaked video mode

Hi,
my first post.

PC-engine hardware permits to switch color clock between 5Mhz and 7Mhz that means it can generate 256 or 320 pixels for each scanline.

I was wondering if something similar can be done on Amiga, in that way more stuff can be moved on the screen, with lower resolution off course.

I don't think ECS or AGA Amigas could change the color clock anyway they can tweak Vsynch and Hsynch timings.

How this can be used to obtain a 256x256 video mode on a regular TV? Maybe a multi-synch monitor is needed? Or is it just impossible?

Thanks,
Ovale
 
AdSense AdSense  
Old 19 September 2008, 20:58   #2
TheDarkCoder
Registered User
 
Join Date: Dec 2007
Location: Dark Kingdom
Posts: 210
Hi!

sei italiano?

You can simply use standard PAL sync but define a display window 256 pixel large. This require less BPL DMA fetches, hence more DMA slots are available for other stuff.

With a multi-sync monitor you can certainly play with non standard frequencies and find a tradeoff that best suits your needs.
Anyway to get 256 horizontal lines, i think you need frequencies similar to the standard PAL

TDC

Quote:
Originally Posted by ovale View Post
Hi,
my first post.

PC-engine hardware permits to switch color clock between 5Mhz and 7Mhz that means it can generate 256 or 320 pixels for each scanline.

I was wondering if something similar can be done on Amiga, in that way more stuff can be moved on the screen, with lower resolution off course.

I don't think ECS or AGA Amigas could change the color clock anyway they can tweak Vsynch and Hsynch timings.

How this can be used to obtain a 256x256 video mode on a regular TV? Maybe a multi-synch monitor is needed? Or is it just impossible?

Thanks,
Ovale
TheDarkCoder is offline  
Old 20 September 2008, 00:09   #3
Ratte
Registered User
 
Join Date: Sep 2008
Location: Germany
Posts: 314
HighGFX offers a 256x192 mode.
(LowRes DoubleScan)
Ratte is offline  
Old 22 September 2008, 15:09   #4
ovale
 
Posts: n/a
Hi TheDarkCoder,
yes I'm Italian, Milan. Are you Italian?

About, your answer. I would like to have a full screen 256xNNN video mode.
I think that just cut the display window is not enough. I'm wrong?

Thanks
 
Old 22 September 2008, 15:15   #5
ovale
 
Posts: n/a
Ratte,
thanks for the hint. Just recently I re-started to have interest on Amiga (I stopped around 1994) so I'm out of synch.

I know that 22Khz (<31Khz) video modes are not viewable on modern multisynch monitors. It's still true?

Do you know if MonitorTVs (LCD TV with VGA/DVI port) support modes with <31Khz ?
At least in theory, they should go down up to 15Khz.

Thanks
 
Old 23 September 2008, 00:26   #6
Cammy
Registered User
Cammy's Avatar
 
Join Date: Aug 2007
Location: Gold Coast, Australia
Age: 32
Posts: 1,134
I'm guessing you want to be able to show a 256x256 image on a PAL screen, but have it completely fill the screen, as traditionally a 320x256 screen would? I would love to know if the Amiga has such a resolution, as the Sega Master System, Mega Drive and Super Nintendo all have a mode where they stretch a lower res image to fill the screen. That's why so many SNES games looked like they had larger sprites and no black borders, not because they had more pixels, but because the screen res was lower than the Amiga but it was stretched to fit the screen.
Cammy is offline  
Old 23 September 2008, 09:15   #7
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,946
You can create 256x256 resolution but it won't be TV compatible (and most likely non-compatible with standard PC monitors too..)

Amiga's pixel clock is not programmable, only way to create custom resolutions is to change start and end position of hsync and vsync (which of course change refresh rates)
Toni Wilen is online now  
Old 23 September 2008, 10:34   #8
TheDarkCoder
Registered User
 
Join Date: Dec 2007
Location: Dark Kingdom
Posts: 210
Quote:
Originally Posted by ovale View Post
Hi TheDarkCoder,
yes I'm Italian, Milan. Are you Italian?

About, your answer. I would like to have a full screen 256xNNN video mode.
I think that just cut the display window is not enough. I'm wrong?

Thanks
ciao

sì, sono abruzzese!

I didn't understand you wanted a full-screen display. You are right, cutting the display window is not enough (although in this way you get more free DMA slots). Then the right answer to your question is the one given by Toni Wilen above. You are forced to a non-standard video frequecy.
TheDarkCoder is offline  
AdSense AdSense  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
The Pixel Nation is Formed.... Lorfarius Retrogaming General Discussion 58 09 November 2012 02:50
Pixel coding Akira Retrogaming General Discussion 9 07 March 2012 23:20
Ateobus and pixel 64 attila06 support.Hardware 9 23 January 2012 22:15
Jumpy video issue in WinUAE 2.3.3 windowed mode P-J support.WinUAE 4 13 January 2012 19:47
'Warp Mode' broken in 'windowed mode' NoX1911 support.WinUAE 3 26 May 2007 02:05

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 17:31.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Page generated in 0.14060 seconds with 14 queries