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Drivers & Software

Adept II
Adept II

Why is alternative DVI operational mode on by default?

I've been having a flickering issue for the past few months with my R9 290 which was driving me nuts. I was about to buy an Nvidia card until I found a post on some forum which suggested turning off alternative DVI operational mode. I tried it and now my issue is completely resolved.  Why is this on by default? IMO this should be off by default

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7 Replies
Esteemed Contributor III

Re: Why is alternative DVI operational mode on by default?

According to ToastyX on 120hz.net: http://120hz.net/showthread.php?1410-Alternate-DVI-operational-mode

"Alternate DVI operational mode" is coherent mode, meaning the clock and data are synchronized. Originally, DVI was non-coherent because the clock multiplier caused a delay in the clock signal that needed to be compensated for at the receiving end. This caused problems when using longer cables because the length affected the delay. Nowadays, everything is designed to use coherent signals for better stability, so this option should be left on. It shouldn't be turned off unless you're using an older non-coherent display.

Esteemed Contributor III

Re: Why is alternative DVI operational mode on by default?

I have the same card and notice the same default setting. I noticed a difference as well....and since then have always disabled it. The same goes for "Surface Format Optimizations" in the Control Panel...it is On by default. Disable that too.

Adept II
Adept II

Re: Why is alternative DVI operational mode on by default?

Thanks. I'm not using a "non-coherent display" though, at least I don't think. It's a fairly new LED monitor. Link​ -- kind of strange that I"m having problems with this on

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Adept II
Adept II

Re: Why is alternative DVI operational mode on by default?

What does 'Surface Format Optimizations' cause for you?

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Esteemed Contributor III

Re: Why is alternative DVI operational mode on by default?

Why aren't you using DisplayPort with that monitor? You will notice a quality difference, at least I did.

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Adept II
Adept II

Re: Why is alternative DVI operational mode on by default?

I didn't have a DP cable and DVI dual link works fine at 1440p. What quality difference did you notice? I thought DP was only better if you need a higher resolution than 1440p which my monitor can't handle anyway

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Esteemed Contributor III

Re: Why is alternative DVI operational mode on by default?

No issues pertaining to DVI. It is just a setting that has been around since the DX9 days and has the effect of lowering some settings to obtain higher (1-2) fps. In effect "ATI surface optimization is automatic FP16 to FP11 format demotion and it affects base texture quality."

If you want the best picture/video disable it.