Bridgeboard built-in CGA 4-color graphics output corruption

superfrog · 22 August 2018, 01:06

Hi Toni, I'll try to make this as easy and proper as possible. I deleted my previous posts in beta thread since they didn't belong there and am reposting here with new test case files (configs, nvr, hdf)

With Bridgeboard emulation, the CGA color text display works fine, but it seems like the 4-color CGA graphics display does not work correctly. I can't verify this worked properly with real HW Bridgeboard, but I know in the official C= docs it says Bridgeboard supports 4-color CGA graphics, and I doubt they would have built a product that claimed 4-color CGA capability and made a board that produced the out of phase output you can see in the attached pics. Not a high priority, but I do think this is something that should work probably work the same with built-in BB CGA emulation and real VGA card emulating CGA. AFAIK this problem has existed for as long as WinUAE BB has.

The test environment is set up so all you have to do is let WB boot up, open PC Color Window, and the CIRCLE.BAS program will automatially run from PC AB virtual hardfile.

If you think this is a problem the real BB had then fine, don't worry about it. But if it's a problem with WinUAE, then I'm hoping it can be fixed. In any case, I'd be curious to hear your thoughts about it.

Thanks!

Files uploaded to The Zone:

http://eab.abime.net/zone/BB%20CGA%2...VGA%20Test.zip

Toni Wilen · 22 August 2018, 11:37

I thought you meant VGA board showing incorrect graphics..

Bridgeboard "built-in" MDA and CGA support is done almost fully in software, all writes go to shared RAM and hardware generates interrupt that tells Janus software that something has changed in video RAM/IO, Janus software then "emulates" it and renders it in Amiga window.

Unless there is some weird remapping going on but at least documentation (A500/A200 Technical Reference Manual which has very detailed address space description) does not mention anything CGA specific.

Perhaps it uses "Graphics" memory access (which is only mentioned in documentation but not described, possibly it does byte swapping). Do you get "ACCESS_MODE_GFX" log messages when running CGA programs? (use -log command line parameter to see it in real time)

EDIT: Yes, it does use "graphics access" (and byte wide which is not logged so it isn't byteswapping but something else..)

Toni Wilen · 22 August 2018, 17:13

Fixed.

Hardware does de-interleaving of CGA bitmap.

CGA graphics mode format is: aabbccdd eeffgghh (aa = color of first pixel, 0-3, bb = color of second pixel and so on..)

Bridgeboard "graphics access" region deinterleaves this so that Amiga side sees it in this format: abcdefgh (original even bits) abcdefgh (original odd bits) and so on..

superfrog · 22 August 2018, 23:38

Quote:

Originally Posted by Toni Wilen

Fixed. Hardware does de-interleaving of CGA bitmap...

Brilliant it looks great now! Thanks so much Toni!

superfrog · 23 August 2018, 00:02

Okay one more problem, if you have the time

In BB built-in CGA emulation, switching from 80-column text mode to 40-column mode works fine. But switching from 40-column back to 80-column mode breaks the display. As you can see in the screenshots, the display shifts halfway to the left and is cut off after switching back to 80-column mode. If you quit PC Color window and restart then the display is back to normal.

Mode switching in CL VGA emulating CGA mode works fine.

I changed the test setup so when the PC side boots it starts the CGA_COMP diagnostics. This is a really nice program (suggested by AnnaWu) for CGA compatibility testing.

If you start with the BB CGA config, let CGA_COMP start, select "Textmode Manipulation >> 40-column display" from the menu. Run the test, let it switch to 40-column mode. Press a key, switch back to 80-column mode. The display is shifted left.

Now, quit PC Window, run again from WB. Display looks good again.

You can even test this from DOS prompt. Quit CGA_COMP program, type "mode co40" at DOS prompt. Now type "mode co80" and switch back to 80-column mode. Same problem.

New test files here:

http://eab.abime.net/zone/BB%20CGA%2...20CGA%20v2.zip

Thanks!

Toni Wilen · 23 August 2018, 21:14

I can't see how UAE can affect CGA emulation this way, especially when display corrects itself when PC window is closed and opened, while PC side does nothing.

-> need real bridgeboard testing.

22 August 2018, 01:06	#1
superfrog Registered User Join Date: Jun 2015 Location: San Francisco, USA Posts: 168	Bridgeboard built-in CGA 4-color graphics output corruption Hi Toni, I'll try to make this as easy and proper as possible. I deleted my previous posts in beta thread since they didn't belong there and am reposting here with new test case files (configs, nvr, hdf) With Bridgeboard emulation, the CGA color text display works fine, but it seems like the 4-color CGA graphics display does not work correctly. I can't verify this worked properly with real HW Bridgeboard, but I know in the official C= docs it says Bridgeboard supports 4-color CGA graphics, and I doubt they would have built a product that claimed 4-color CGA capability and made a board that produced the out of phase output you can see in the attached pics. Not a high priority, but I do think this is something that should work probably work the same with built-in BB CGA emulation and real VGA card emulating CGA. AFAIK this problem has existed for as long as WinUAE BB has. The test environment is set up so all you have to do is let WB boot up, open PC Color Window, and the CIRCLE.BAS program will automatially run from PC AB virtual hardfile. If you think this is a problem the real BB had then fine, don't worry about it. But if it's a problem with WinUAE, then I'm hoping it can be fixed. In any case, I'd be curious to hear your thoughts about it. Thanks! Files uploaded to The Zone: http://eab.abime.net/zone/BB%20CGA%2...VGA%20Test.zip Attached Thumbnails Last edited by superfrog; 22 August 2018 at 01:19. Reason: Attach screenshots

22 August 2018, 11:37	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	I thought you meant VGA board showing incorrect graphics.. Bridgeboard "built-in" MDA and CGA support is done almost fully in software, all writes go to shared RAM and hardware generates interrupt that tells Janus software that something has changed in video RAM/IO, Janus software then "emulates" it and renders it in Amiga window. Unless there is some weird remapping going on but at least documentation (A500/A200 Technical Reference Manual which has very detailed address space description) does not mention anything CGA specific. Perhaps it uses "Graphics" memory access (which is only mentioned in documentation but not described, possibly it does byte swapping). Do you get "ACCESS_MODE_GFX" log messages when running CGA programs? (use -log command line parameter to see it in real time) EDIT: Yes, it does use "graphics access" (and byte wide which is not logged so it isn't byteswapping but something else..) Last edited by Toni Wilen; 22 August 2018 at 16:17.

23 August 2018, 00:02	#5
superfrog Registered User Join Date: Jun 2015 Location: San Francisco, USA Posts: 168	Okay one more problem, if you have the time In BB built-in CGA emulation, switching from 80-column text mode to 40-column mode works fine. But switching from 40-column back to 80-column mode breaks the display. As you can see in the screenshots, the display shifts halfway to the left and is cut off after switching back to 80-column mode. If you quit PC Color window and restart then the display is back to normal. Mode switching in CL VGA emulating CGA mode works fine. I changed the test setup so when the PC side boots it starts the CGA_COMP diagnostics. This is a really nice program (suggested by AnnaWu) for CGA compatibility testing. If you start with the BB CGA config, let CGA_COMP start, select "Textmode Manipulation >> 40-column display" from the menu. Run the test, let it switch to 40-column mode. Press a key, switch back to 80-column mode. The display is shifted left. Now, quit PC Window, run again from WB. Display looks good again. You can even test this from DOS prompt. Quit CGA_COMP program, type "mode co40" at DOS prompt. Now type "mode co80" and switch back to 80-column mode. Same problem. New test files here: http://eab.abime.net/zone/BB%20CGA%2...20CGA%20v2.zip Thanks! Attached Thumbnails

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22 August 2018, 17:13	#3
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	Fixed. Hardware does de-interleaving of CGA bitmap. CGA graphics mode format is: aabbccdd eeffgghh (aa = color of first pixel, 0-3, bb = color of second pixel and so on..) Bridgeboard "graphics access" region deinterleaves this so that Amiga side sees it in this format: abcdefgh (original even bits) abcdefgh (original odd bits) and so on..

23 August 2018, 21:14	#6
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	I can't see how UAE can affect CGA emulation this way, especially when display corrects itself when PC window is closed and opened, while PC side does nothing. -> need real bridgeboard testing.

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