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Monitor Degradation? Is my OC safe?
07-31-2017, 12:01 AM (This post was last modified: 07-31-2017 12:32 AM by gran172.)
Post: #1
Monitor Degradation? Is my OC safe?
So basically I used CRU to overclock my monitor to 75hz, I had to use LCD Reduced mode (which lowers pixel clock, because otherwise it was unstable).

I remember being able to overclock with factory pixel clocks to 70-74hz before, now after months of using a reduced pixel clock, my monitor only overclocks to about 65-66hz.

Weird thing is, monitor works just fine at 75hz with the reduced pixel clock, no frame skipping and I saw artifacts only once (which was weird, never happened again after that).

So, is this degradation? Should I be safe to keep running at 75hz on a lower pixel clock, or should I just leave everything at stock?

I searched everywhere to read some more about monitor overclocking and pixel clocks but found nothing.

So I just downloaded Toasty's Pixel Patcher and I'm now able to get 74hz without changing timings at all, I'm guessing I should be fine?
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07-31-2017, 09:37 PM
Post: #2
RE: Monitor Degradation? Is my OC safe?
75 Hz would not degrade a typical monitor. What monitor is this? What video card do you have? Are you using DVI? HDMI? DisplayPort? What resolution are you talking about? What do you mean by unstable?
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07-31-2017, 10:05 PM (This post was last modified: 07-31-2017 10:06 PM by gran172.)
Post: #3
RE: Monitor Degradation? Is my OC safe?
(07-31-2017 09:37 PM)ToastyX Wrote:  75 Hz would not degrade a typical monitor. What monitor is this? What video card do you have? Are you using DVI? HDMI? DisplayPort? What resolution are you talking about? What do you mean by unstable?

Hey mate, so I installed your pixel clock patcher and now my monitor overclocks just fine to 74hz without using LCD reduced, so I'm guessing I should be good haha, thanks for taking your time to answer Smile

LG22MP55, GTX 1060 6Gb, DVI-D (can't remember if SL or DL), 1080p. When I was at 75hz with LCD Reduced I would get some small artifacts (I think those were artifacts, my desktop wallpaper was black and there were some small coloured pixels that were not supossed to be there).

By the way, I've been trying to find info on the topic everywhere but I can't seem to find any good info, what's the impact of reducing pixel clock on a monitor overclock?

You seem to recommend to use LCD Standard, but default timings (in CRU it appears as "Manual") puts me at 183mhz on 74hz, LCD Standard puts me at 172mhz on 74hz and LCD Reduced puts me at 165mhz on 74hz, which one should I use?

Also, any reason why you recommend to use LCD Standard while if you overclock your display with the Nvidia CP it uses higher pixel clock values than LCD Standard? (NVCP would use 183mhz, while LCD Standard on CRU would use 172mhz).

Sorry if I asked too many questions, I just couldn't find any good info on the topic and you seem to know your stuff. Once again, thanks for taking your time to read.
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08-01-2017, 09:28 AM
Post: #4
RE: Monitor Degradation? Is my OC safe?
DVI normally switches to dual-link beyond 165 MHz pixel clock, but that monitor has single-link DVI. That's why it won't display correctly beyond 165 MHz pixel clock without the patch. The patch raises the switchover point to 230 MHz.

The pixel clock is just the total number of pixels per second (horizontal total * vertical total * refresh rate). Reducing the totals reduces the pixel clock, which reduces the bandwidth required. "LCD reduced" will make sure the pixel clock doesn't exceed 165 MHz at 74 Hz. Keep in mind though that NVIDIA cards will not clock down when idle if the vertical blanking/total is too low. "LCD standard" will make sure the vertical blanking/total is high enough for any video card. Other than that, the timing parameters don't really matter much as long it works. The point of standards is to make sure certain timing parameters are always supported, but if you're trying refresh rates that the monitor doesn't officially support, then there's no way to know what will work without trial and error.

The values that CRU fills in by default when you click "Add..." are just the CEA-861 standard timing parameters for 1920x1080 @ 60 Hz. This would give you 183.15 MHz at 74 Hz. This is similar to what the NVIDIA control panel does by default. "LCD native" at 74 Hz should give you the same timing parameters. This is technically not standard at 74 Hz because the timing parameters were intended for 60 Hz, but this can help make higher refresh rates work with some 1920x1080 monitors and TVs. "LCD standard" uses the CVT-RB standard at 74 Hz. The NVIDIA control panel calls this "CVT reduced blank." This would give you 172.24 MHz at 74 Hz.
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08-01-2017, 04:22 PM (This post was last modified: 08-01-2017 05:06 PM by gran172.)
Post: #5
RE: Monitor Degradation? Is my OC safe?
(08-01-2017 09:28 AM)ToastyX Wrote:  DVI normally switches to dual-link beyond 165 MHz pixel clock, but that monitor has single-link DVI. That's why it won't display correctly beyond 165 MHz pixel clock without the patch. The patch raises the switchover point to 230 MHz.

The pixel clock is just the total number of pixels per second (horizontal total * vertical total * refresh rate). Reducing the totals reduces the pixel clock, which reduces the bandwidth required. "LCD reduced" will make sure the pixel clock doesn't exceed 165 MHz at 74 Hz. Keep in mind though that NVIDIA cards will not clock down when idle if the vertical blanking/total is too low. "LCD standard" will make sure the vertical blanking/total is high enough for any video card. Other than that, the timing parameters don't really matter much as long it works. The point of standards is to make sure certain timing parameters are always supported, but if you're trying refresh rates that the monitor doesn't officially support, then there's no way to know what will work without trial and error.

The values that CRU fills in by default when you click "Add..." are just the CEA-861 standard timing parameters for 1920x1080 @ 60 Hz. This would give you 183.15 MHz at 74 Hz. This is similar to what the NVIDIA control panel does by default. "LCD native" at 74 Hz should give you the same timing parameters. This is technically not standard at 74 Hz because the timing parameters were intended for 60 Hz, but this can help make higher refresh rates work with some 1920x1080 monitors and TVs. "LCD standard" uses the CVT-RB standard at 74 Hz. The NVIDIA control panel calls this "CVT reduced blank." This would give you 172.24 MHz at 74 Hz.

Actually, my monitor has Dual Link DVI-D (got my displays name wrong, it's actually a LG 22MP55D) but I'm using a Single Link DVI-D cable, not sure if that has any impact on anything? The NVCP says I'm using a DVI-D Dual Link connection though (at least that's what the little picture shows).

I see, so when I got those "artifacts" at 74hz while using LCD Reduced, could it be that the pixel clock was actually too low so it wouldn't display all the pixels correctly, because of not having enough bandwidth?

So I guess I'll just stick to LCD Standard and 75hz then, this webiste (http://es.all-specs.net/model/776527/) says my monitor supports 56-75hz (although for some reason I can downclock to 50hz) so I guess I should be fine.

Thanks a lot for the help Toasty Smile

EDIT: Actually, I tested 75hz with LCD Standard three times, one it was fine but the other two I got "no signal", that's kinda weird, should I just keep it at 74hz?
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08-02-2017, 01:13 AM
Post: #6
RE: Monitor Degradation? Is my OC safe?
(08-01-2017 04:22 PM)gran172 Wrote:  Actually, my monitor has Dual Link DVI-D (got my displays name wrong, it's actually a LG 22MP55D) but I'm using a Single Link DVI-D cable, not sure if that has any impact on anything? The NVCP says I'm using a DVI-D Dual Link connection though (at least that's what the little picture shows).
The monitor has single-link DVI. The video card has dual-link DVI. The video card doesn't detect what the monitor has. DVI normally sends a dual-link signal beyond 165 MHz without the patch.


(08-01-2017 04:22 PM)gran172 Wrote:  I see, so when I got those "artifacts" at 74hz while using LCD Reduced, could it be that the pixel clock was actually too low so it wouldn't display all the pixels correctly, because of not having enough bandwidth?
No, the totals always includes all the pixels, so there's always enough bandwidth. The monitor might not be able to handle lower values because of processing limitations, but that's monitor-specific.


(08-01-2017 04:22 PM)gran172 Wrote:  EDIT: Actually, I tested 75hz with LCD Standard three times, one it was fine but the other two I got "no signal", that's kinda weird, should I just keep it at 74hz?
Sometimes if you're at the edge of what the monitor will accept, it will work sometimes and not others. Usually this is a monitor-specific limitation and not a pixel clock limitation. Sometimes different timing parameters can help even if the pixel clock is higher, so check if "LCD native" works better for 75 Hz. If not, use 74 Hz.
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