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Old 18 May 2020, 20:46   #1
Quaxo76
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Graphical glitch with some processors

Hello,
I have almost completed setting up a ClassicWB HDF image with all my games, so I started "testing" them - i.e. playing...
I have found a pretty annoying bug/glitch. On many games - for example it's very evident in Nitro - you can see flashing memory patterns on the background graphics. Some games are more affected than others, while others not at all. If I use a 68000 or 68010 CPU, it works fine but is of course slow. Any CPU 68020 or above shows the glitch. But I would like to use at least a 68030.
I haven't been able to find any other setting that influences the glitch.

My real Amiga 1200 isn't hooked up at the moment, but I seem to recall that it was NOT showing the bug with ClassicWB and a 68030 accelerator board.


Is this known, and does it have a fix? I'm using FS-UAE on Linux.


Thank you,
Cristian
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Old 18 May 2020, 21:05   #2
jotd
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probably blitter bugs. Your emulator probably has an "immediate blitter" or "wait for blitter" option.

There's also the whdload option. We use to fix self-modifying/blitter/speed issues that often result in trashed gfx or sound.
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Old 20 May 2020, 14:59   #3
Quaxo76
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Thank you, so, is there some setting I should try to have the glitch disappear? I looked in the options page and I couldn't find anything about the blitter...

Cristian

EDIT:
Taking "Nitro" as an example, if I emulate a PAL Amiga, the glitch is in the main game screen. If I emulate a NTSC Amiga, the game screen is perfect, but the glitch appears in the screens between races.

I attached two screenshots showing a normal screen, and a "glitched" screen.

http://eab.abime.net/attachment.php?...1&d=1589980353
http://eab.abime.net/attachment.php?...1&d=1589980330
Attached Thumbnails
Click image for larger version

Name:	a12008gbnuovo-real-2005201507-03.png
Views:	48
Size:	136.7 KB
ID:	67429   Click image for larger version

Name:	a12008gbnuovo-real-2005201507-01.png
Views:	51
Size:	268.2 KB
ID:	67430  

Last edited by Quaxo76; 20 May 2020 at 15:13.
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Old 20 May 2020, 16:40   #4
FrodeSolheim
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You can try the option
Code:
uae_immediate_blits = true
or https://fs-uae.net/docs/options/uae-waiting-blits

These options need to be typed manually into custom configuration in FS-UAE Launcher.

You can also set these options dynamically from the Amiga side via the
uae-configuration
tool shipped with WinUAE.
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Old 21 May 2020, 11:51   #5
PeterK
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@FrodeSolheim

Unfortunately, your MOVEM.W Jit bug still exists in FS-UAE 3.0.5:

https://eab.abime.net/showpost.php?p...3&postcount=45
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Old 21 May 2020, 12:34   #6
jotd
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using JIT for games is a lost cause. Some games (specially the ones written in assembly) use self-modifying code now and then. And sometimes the modifications are so far from the execution that even 68060 processors have their caches flushed before the modified code is executed. But with JIT, it's not guaranteed at all.

JIT also speeds up things in an unbelievable way, so sometimes the programmer inserts a VPOS wait loop, does something, and relies on the fact that VPOS changed a little bit for the next VPOS wait loop, but with JIT it's very possible that it does not... and here goes your timing bug.

When developping fixes for whdload, I use JIT when I want to make sure that there's no SMC. Otherwise it's too much work fixing the games. I consider games "fixed" when they work with "fastest/no JIT" option, which is something we'll tend to get with new FPGA accelerators.
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Old 21 May 2020, 12:46   #7
PeterK
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My hint about the jit bug was not related to issues in any games, I just made it in this thread, because FrodeSolheim posted here yesterday and hence it's more likely to get his attention.
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