Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
Tue, 20 Mar 2018 20:18:16 + Xianwen Chen > [...] > If you are right that humans are not able to see the difference between 60 Hz > and 59.95 Hz, then something is wrong with xrandr that the actual refresh > rate is quite below 60, not as much as 59.95 as reported by xrandr, because I > can clearly see the flickering. I do not think that this is a minimal thing, > because the flickering screen makes my head dizzy. > > I do not think that there is problem with the connection cable, as there was > no such problem when the same external monitor is connected to a ThinkPad R52 > using the same VGA cable a couple of days ago. I can check the cable > connection again tomorrow. > > I am sceptical whether there is any other source of distortion. I don't know > where to start if there should be distortion. > > Yours sincerely, > Xianwen > Hi Xianwen, Most probably it is NOT the refresh rate and xrandr is reporting it fine. I would recommend you find the source of interference: in a closed ground loop, electrical current between various signalling cables, nearby USB ?! cables close to the video cable or other signal cables, and power circuit plug orientation, noise in the electric mains power from other equipment. Also some monitors have PWM flickering quite visible on low settings, yet I suspect you have a signalling interference and closed ground loop case. Kind regards, Anton Lazarov
Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
> > Dear Mihai, > > Although your tone in your email was not pleasant, > > You are posting to OpenBSD-misc. Objectionable tone is very common, > particularly for users who *appear* to be complaining about > immeasurably-small problems that aren't actually significant in the real > world. If you wish to remain an OpenBSD user, get used to people being > rude. (I am not going to speculate whether this is good or bad, but it > is the case.) Hi Adam. Shut up -- you have behaved far worse in the past. In fact, you should apologize for intruding with your invalid perspective.
Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
On 2018-03-20 15:18, Xianwen Chen wrote: Dear Mihai, Although your tone in your email was not pleasant, You are posting to OpenBSD-misc. Objectionable tone is very common, particularly for users who *appear* to be complaining about immeasurably-small problems that aren't actually significant in the real world. If you wish to remain an OpenBSD user, get used to people being rude. (I am not going to speculate whether this is good or bad, but it is the case.) If you are right that humans are not able to see the difference between 60 Hz and 59.95 Hz, then something is wrong with xrandr that the actual refresh rate is quite below 60, not as much as 59.95 as reported by xrandr, because I can clearly see the flickering. I do not think that this is a minimal thing, because the flickering screen makes my head dizzy. Then my suggestion would be to replace the lights in your room, not try to fix a 0.05Hz deviation. The vast majority of systems I own report that the LCDs actually run at 59.95Hz; I've only seen one or two that ever reported 60Hz. This is normal. In a worst-case scenario, room lighting that is at a very slightly different frequency can cause odd effects, this is known as interference, and can produce a "beat frequency". If the difference is small it's possible you could experience this as flickering. (I believe the flickering is actually an neuro-optical illusion, but you might still be experiencing it.) I do not think that there is problem with the connection cable, as there was no such problem when the same external monitor is connected to a ThinkPad R52 using the same VGA cable a couple of days ago. I can check the cable connection again tomorrow. That is irrelevant. You have measured one VGA driver against a completely different VGA driver. Different laptops = different electronics = different results. I am sceptical whether there is any other source of distortion. I don't know where to start if there should be distortion. Fluorescent lights, or cheap LED lights - anything that needs a ballast or rectifier. Any of these things can cause not only the beat frequency optical interference mentioned above, but ALSO can cause electromagnetic interference in the cable. Oh, and cheap USB chargers are another common source of really bad EM interference. And guess what's almost immune to this type of EM interference? HDMI, DVI-D or DP cables. Guess what's REALLY susceptible? VGA cables. Hmm. The exact frequency of a monitor, regardless of type, is almost always irrelevant to human eyes. Whether it's 30Hz, 47.8Hz, 59.95Hz or 60.0Hz As you are apparently experiencing real problems, I would check, in order: 1. your cable - switch to HDMI (or HDMI->DVI or HDMI->DP) and get rid of VGA **immediately**. 2. your lights - try it with all the lights EXCEPT regular incandescent / halogen lights turned off. 3. your eyes - get a thorough examination by a doctor; there are some rare conditions that could cause odd things like this. 4. your brain - make sure you don't have a brain tumour (yes, I'm serious, it can cause things like this!) As to the VGA cable - this is such an important point that I agree with Nick - please go away and don't complain further until you have switched to a digital connection of some sort. I recall that my Dell E6430 was quite capable of producing so-called "120Hz" digital signals, and yours is a generation newer than that. I am 99% certain that your problem will go away with a different cable. (If you want DVI + DP connectors instead of HDMI, buy a Dell E-series dock on eBay for $50.) -Adam
Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
On 2018-03-20, Xianwen Chen wrote: > Dear OpenBSD users, > > I run OpenBSD 6.2 amd64 on a Dell Latitude E6540 laptop. > > I hook a Dell U2412M monitor to the laptop using VGA port. So you have a pretty decent monitor and laptop, but you're using an analogue connection (which means: digital generation, converted to analogue in the laptop, sent over a cable, sampled at the monitor to convert back to digital), at a resolution and refresh rate which is right at the practical limit for the cable. I think you'll be a lot happier if you get an HDMI-DisplayPort cable and switch to a digital connection.
Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
On 03/20/18 11:49, Xianwen Chen wrote: > Dear OpenBSD users, > > I run OpenBSD 6.2 amd64 on a Dell Latitude E6540 laptop. > > I hook a Dell U2412M monitor to the laptop using VGA port. xrandr > recognizes the maximum resolution of the external monitor, but the > refresh rate is slightly below 60: > VGA-1 connected (normal left inverted right x axis y axis) >1920x1200 59.95 + ... > I can visibly see the flickering of the screen on the external monitor. > Is this because the refresh rate is below 60? no. And I'm stopping your message here, as you are barking up the wrong tree. For 60hz, 59.95 is more than "close enough". Plus, LCD monitors are NOT like CRTs in refresh. CRTs draw one scan line at a time, that scan line and a few above it are lit up at any moment, so the entire screen flashes at the refresh rate. 60hz is about the minimum that is tolerable for most people, and many people can "feel" (if not exactly see) the difference for significantly faster refresh rates (and the faster, the better) LCDs have a much more static picture. The screen refresh rate will matter for how smooth motion can appear, but the screen itself does NOT flicker. Prove this to yourself by holding your hand out, fingers spread, and waving it back and forth rapidly in front of a CRT (if you can find one) and an LCD monitor. You will see very different results. Most likely what you are seeing is your monitor having a bad time with the timing of the computer. I suspect the "Auto-adjust" button will do wonders, but I have also found that some computers just put out garbage to the analog video port. And in one case, I found that having both the VGA and HDMI cable attached to the monitor, even though only the VGA was attached to the computer, caused annoying flicker on the monitor that mostly went away when I happened to need that HDMI cable elsewhere. Nick.
Re: Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
Dear Mihai, Although your tone in your email was not pleasant, I would still like to thank you for your response, because it contained helpful information, see below. I have searched around, read, and tried to fix the problem myself for a couple of days now. I searched misc's archive on-line and did not find more useful email conversations. If you know some messages on misc that contain helpful information, could you point me to them? If you are right that humans are not able to see the difference between 60 Hz and 59.95 Hz, then something is wrong with xrandr that the actual refresh rate is quite below 60, not as much as 59.95 as reported by xrandr, because I can clearly see the flickering. I do not think that this is a minimal thing, because the flickering screen makes my head dizzy. I do not think that there is problem with the connection cable, as there was no such problem when the same external monitor is connected to a ThinkPad R52 using the same VGA cable a couple of days ago. I can check the cable connection again tomorrow. I am sceptical whether there is any other source of distortion. I don't know where to start if there should be distortion. Yours sincerely, Xianwen On Tue, Mar 20, 2018 at 6:22 PM, Mihai Popescu mailto:mih...@gmail.com>> wrote: Hello, It looks like you have some problems in setting up OpenBSD. The misc@ has some messages with your problems. I think you started on the wrong foot: using OpenBSD is not like trying to replace Windows or Linux. Stop making noise of minimal things and try to read more on man pages and message lists. 1920x1200 59.95 + This, compared to 60 Hz is like 0.05 Hz difference. Seriously, can you grasp that? Can you say the time difference? Sometimes, the electronics is not able to do a perfect X frequency. Please, do not say you can see flicker at 60 Hz. No human can do that until now. If you really see some flickering, it must be from an imperfect connection cable or other source of distorsion. Have fun.
Dell Latitude E6540 OpenBSD 6.2 amd64 freezes when adjusting refresh rate using xrandr
Dear OpenBSD users, I run OpenBSD 6.2 amd64 on a Dell Latitude E6540 laptop. I hook a Dell U2412M monitor to the laptop using VGA port. xrandr recognizes the maximum resolution of the external monitor, but the refresh rate is slightly below 60: VGA-1 connected (normal left inverted right x axis y axis) 1920x1200 59.95 + 1920x1080 60.00 1600x1200 60.00 1680x1050 59.95 1280x1024 60.02 1280x960 60.00 1024x768 60.00 800x600 60.32 640x480 60.00 720x400 70.08 I can visibly see the flickering of the screen on the external monitor. Is this because the refresh rate is below 60? At the back of the monitor, a label states that the monitor supports a resolution of 1920x1200 at 60 refresh rate. I tried to use xrandr to adjust refresh rate. I ran $ gtf 1920 1200 60 The output is: # 1920x1200 @ 60.00 Hz (GTF) hsync: 74.52 kHz; pclk: 193.16 MHz Modeline "1920x1200_60.00" 193.16 1920 2048 2256 2592 1200 1201 1204 1242 -HSync +Vsync $ nice -n 20 xrandr --newmode "1920x1200_60.00" Modeline "1920x1200_60.00" 193.16 1920 2048 2256 2592 1200 1201 1204 1242 -HSync +Vsync $ xrandr --addmode VGA-1 1920x1200_60.00 $ xrandr --output VGA-1 --mode 1920x1200_60.00 Then the entire laptop freezes. The keyboard is not responding, nor is the mouse or touchpad. The system is somehow running though, as the system gracefully shuts down when I press the power button. Do you have experience with setting up refresh rate on an external monitor? Yours sincerely, Xianwen
