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Old 11 August 2016, 12:01   #1
Foebane
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Grapical artefacts on the left-hand side only

One thing I've noticed in all my months of Amiga emulation lately, is how, when displayed on a widescreen PC screen with overscan on all four sides, how in most demos, and most likely a lot of games, how there seem to be artefacts caused by the custom chipset on only the left-hand side of the screen, as if it's unavoidable. Is this a side-effect of the way the Amiga chipset works?

It could simply be that on emulation on modern PCs with widescreen monitors, we are simply seeing parts of the image, almost always overscan, that would've been hidden on old CRT 4:3 TVs in the past. After all, I vaguely remember seeing "overscan activity" on my A500 back in the day, and on my old Atari 800XL as well (yes, and emulation).

There is an option on Altirra (the 800XL emulator) to remove this overscan baggage - is there an option on WinUAE to do the same? I somehow doubt it, as overscan is important to the Amiga, no matter what artefacts show up as a result of chipset activity.
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Old 11 August 2016, 15:43   #2
Toni Wilen
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Quote:
Originally Posted by Foebane View Post
Is this a side-effect of the way the Amiga chipset works?
It is just coders not noticing bad display setup. It is easy to miss without 1081 or similar monitors with adjustable display position/width.

Quote:
There is an option on Altirra (the 800XL emulator) to remove this overscan baggage - is there an option on WinUAE to do the same? I somehow doubt it, as overscan is important to the Amiga, no matter what artefacts show up as a result of chipset activity.
If I am not completely wrong, 8-bit Ataris only had very few width hardware options. Amiga is fully programmable (both width _and_ position), which means no one can agree which is "correct" output, especially because 1081/1084-type monitors were quite common.

Filter panel has "overscan blanking" option that can be used to hide overscan regions.
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Old 11 August 2016, 17:09   #3
Foebane
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Yes, I realise now it IS down to the coding, and I see it much more often in demos, which are usually released to ridiculously tight deadlines and so are rushed a lot of the time, no time to clean up, etc.

I'll look at that option you mentioned some time, though - I can't do it at the moment as I'm housesitting elsewhere.
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