C27F591 OC, some questions from newbie

[C27F]

Hi,
recently I bought Samsung C27F591 which is supposed to run easily with 72hz refresh rate. The only problem I have is that I don't know what settings are most safe.

I can create custom resolution in intel control panel but I have to pick from a few standards, here they are: GTF, CVT, CVT-RB, CEA 861. Monitor seems to work with first three ones, I didn't test the last one. What bothers me though is that I have literally no idea what these settings actually are and which one is the best for my monitor. None of them produces any glitches, however I still feel concerned about longevity of my monitor. Even worse it does seem that neither of this option uses the same sync polarity as my monitor natively uses. When I go to monitor menu and check information tab, it says something like "80.4khz, 72hz, NP" with one standard and PN with other. Does this refer to sync polarity? If I set monitor to native full hd 60hz it says "PP" which corelates to +/+ which is native polarity for that resolution and refresh rate. Is this a problem? On the one hand I heard sync polarity should be the same as monitor native, but on the other hand this very monitor uses different sync polarities depending on resolution:

http://downloadcenter.samsung.com/conten...8A-Eng.pdf (page 36)

This very sheet also says max pixel clock for my monitor is 148mhz, this is another (after sync polarity) thing that I don't understand. From what I get this has somethig to do with the amount of pixels that run through my monitor. Does running my monitor at higher pixel clocks damage it over time? What about these other settigns i can change in CRU? If, for example I set, let's say, blanking too high or too low, can it damage my monitor? The same question applies to other parameters. What if for example i set the refresh rate to 240hz, will it burn my monitor immediately? Alaso I noticed that when I use a non standard refresh rate, I can;t change hdmi black level option in monitor menu. It keeps the last setting. Is it normal? Also, If my monitor can run at these 72 hz, does it mean it can also run any refresh rate lower than that assuming all other settings stay the same?

These above are questions that I ask out of curiosity, the only one that is really improtant to me is what are the best 72 hz settings for my monitor, should the sync polarity remain +/+ (it's the same polarity as for native resolution and refresh rate), or it doesn;t matter? If my monitor can run these 72hz at "LCD native" preset, should I keep it, or change to "LCD reduced" in order to lower pixel clock speed (178mhz vs 160mhz) or maybe I should switch to LCD standard and then manually set polarity to +/+ (it's +/- by default)?

I add a few screens that show how these settings look like for me: http://imgur.com/a/ZMexh

The monitor is connected via HDMI cable.

Any information would be really helpful.

[ToastyX]

Short answer: The timing parameters don't matter much. Use whatever works. I would use CVT-RB or "LCD standard" if that works because that is intended for LCD monitors and uses less bandwidth than GTF and CVT.

Long answer: The timing parameters don't do anything that would damage an LCD monitor. The timing parameters mainly specify how long the blanking period is. Blanking is the period between each line (horizontal blanking) and each frame (vertical blanking). The original purpose of blanking was to give CRT monitors time to move the electron gun between lines and frames. This is not as important with LCD monitors, so the blanking can be reduced. If the blanking is too low, the monitor might not display the resolution correctly, but it won't damage the monitor. If the blanking is too high, you're just wasting bandwidth.

Blanking = front porch + sync pulse width + back porch. The front porch is the period before the sync pulse. The sync pulse marks the start of the next line (horizontal sync) or frame (vertical sync). The back porch is the period after the sync pulse. The sync polarity is simply whether the voltage goes up (+) or down (-) for the sync pulse. Monitors can handle both, so it doesn't matter.

Monitor specs are generally useless and don't tell what the monitor can actually do. The "max pixel clock" of 148.5 MHz is simply the pixel clock at 1920x1080 @ 60 Hz with the CEA-861 standard timing parameters because that's the maximum resolution defined by default. The pixel clock is the total number of pixels per second including blanking (horizontal total * vertical total * refresh rate).

The point of standards is to make sure certain values always work so devices can operate with each other. If you're trying refresh rates that the monitor doesn't officially support, there's no guarantee that any particular timing parameters will work, but Samsung monitors are generally not strict about timing parameters as long as the refresh rate is within range. Samsung monitors usually accept up to 77 Hz. Lower refresh rates are possible, but monitors often reject refresh rates below 50 Hz. If the monitor can't handle the resolution or the timing parameters, it will either reject the resolution with an "out of range" or similar message, or it will not display correctly.

GTF is an old standard superceded by CVT. CVT-RB was designed to reduce blanking for LCD monitors. CEA-861 is a standard that defines specific TV resolutions like 1920x1080 @ 60 Hz. HDMI color format options are usually only available with CEA-861 resolutions.

The polarity is not important. GTF and CVT always use -/+ (NP). CVT-RB always uses +/- (PN). CEA-861 uses +/+ (PP) for 1920x1080 and 1280x720.

CRU has timing options organized by purpose instead of by standard:

• "LCD standard" uses CEA-861 and VESA DMT for common TV resolutions and CVT-RB for everything else.
• "LCD native" uses the "LCD standard" timing parameters for 60 Hz. I included this because some TVs can't handle higher refresh rates with CVT-RB.
• "LCD reduced" uses non-standard timing parameters to reduce the pixel clock for some resolutions. I included this to keep certain resolutions like 1920x1080 @ 72-77 Hz from exceeding 165 MHz pixel clock so it will work with single-link DVI and old versions of HDMI without the pixel clock patch.
• "CRT standard" uses the CVT timing standard.
  

[C27F]

Wow, thank you so much, there more informations in your one response than everything I was able to find on the internet about this subject! I'd recommend making some article on this topic, there seem to be nothing of that sort on the internet at the moment.

I tried to run my monitor at higher than 72hz refres rates but it doesn't work even with LCD reduced.

Thank you again!