Changing the display mode (resolution and/or refresh rate) causes the screen to flicker or go dark for a few seconds before the image stabilizes. At least this happens on all laptops and desktops I've used. Why ?  As , when using a complex operating system, part of the delay is due to the display software. However I'm not interested in the "software" delay due to heavy user-interfaces and window management, but only in the "hardware" delay which causes flickering, backlight blinks, etc.  This flickering and delay happens between the firmware greet (bios/efi) and the first installed software (OS splash or bootloader), and the same happens when changing resolution from within all the windows and linux versions I've tried, so it obviously has nothing to do with higher level software such as graphical shells or windows managers.  I see multiple (hypothetical!) causes:   Physical delay ?, like for old CRT display there was a low noise probably indicating the power electronics driving the electron beam was reset. Maybe on LCD the backlight power is reset, which causes flickering and delay, but why does it have to be reset? Very slow protocol ? Brian suggested that the resolution change protocol between the GPU and the display panel is slow. Experience shows that the flickering is not as long on newer laptop, which points in this direction. What I don't get is this : listing available resolutions and sending the desired one should take a few (kilo) bytes and video signals transit @Gbps speeds and a few ms latencies, so how come it takes around a second to negotiate a resolution change ? Display embedded electronics reconfiguration : kreemoweet states on  question that there is no protocol involved but each frame caries its resolution. When a frame has a different resolution than the last, the on-board electronics driving the display needs to be reconfigured: registers and buffers are reallocated, etc. The details are blurry but the electronics can efficiently process the video frames once configured, but takes a (relatively) long time to get configured. Maybe some other reason ?
Why does it take so long for a computer monitor to change resolution? Why does it take 2-3 seconds rather than, say, 50 ms?  E.g. my current Windows 7 with strong GPU and 24 inch monitor takes 2-3 seconds. Why so long? I know some might say "it's JUST 2 seconds", but come on... Games produce hundreds of FPS, and monitors work at 60 Hz, so what is it that takes so much time?  I remember this was the same in just about any machine I ever worked with.
How to isolate the text from a bitmap logo? Given fields $K\subseteq L$, why does $f,g$ relatively prime in $K[x]$ imply relatively prime in $L[x]$? $K,L$ are fields, $K\subseteq L$. $f,g \in K[x]$. Suppose that $f,g$ are relatively prime as elements of $K[x]$. Prove they remain relatively prime  in $L[x]$.  I've tried everything I can think of. I feel like working with the contrapositive may be helpful but that's just a feeling. Presentation of SL$(n,\mathbb{Z}_p)$ Getting the location from an IP address I want to retrieve information like the city, state, and country of a visitor from their IP address, so that I can customize my web page according to their location. Is there a good and reliable way to do this in PHP? I am using JavaScript for client-side scripting, PHP for server-side scripting, and MySQL for the database. The total number of locks exceeds the lock table size How do I prevent the blank screensaver when using keyboard shortcut to lock the computer? What is the correct name to use with /give for Lapis Lazuli? In Minecraft, when cheats are enabled you can give yourself items using the command /give [user] [item] [count], e.g. /give user45623 dirt 32. What is the item name to use for Lapis Lazuli? I've tried lapis_lazuli, lapis, lazuli, dye4, and dye_4, but it's none of those. Why is df missing 500MB of available space? I've just had a message today from Ubuntu 11.04 that I have only 100 MB left, so I cleaned up some files, and I got 200 MB. Then, after a couple of hours, suddenly I have only 26 MB?! I tried df, du via mount --bind, /forcefsck with reboot - nothing could should what the culprit is - finally I searched big files, realized /var/log/syslog is 100MB+ and /var/log/kern.log is 200MB+ - blanked them with sudo bash -c 'echo &gt; ...' and rebooted, and now I have some spare MB.  But now, I realize I have another problem with df:  $ df -h Filesystem            Size  Used Avail Use% Mounted on /dev/sda5             9,7G  8,8G  385M  96% / none                  963M  696K  962M   1% /dev none                  969M   12K  969M   1% /dev/shm none                  969M  252K  969M   1% /var/run none                  969M     0  969M   0% /var/lock /dev/sda6             9,7G  8,1G  1,1G  89% /media/disk  $ df -h --block-size M Filesystem           1M-blocks      Used Available Use% Mounted on /dev/sda5                9845M     8960M      385M  96% / none                      963M        1M      962M   1% /dev none                      969M        1M      969M   1% /dev/shm none                      969M        1M      969M   1% /var/run none                      969M        0M      969M   0% /var/lock /dev/sda6                9845M     8235M     1110M  89% /media/disk   Note so for /, it says there are 9845M total; and Used 8960M - then remaining would be 9845-8960 = 885 M, however, here I have only 385M Available.  Also, for /media/disk, it says total 9845M, Used 8235M - then remaining would be 9845-8235 = 1610, however, here I have only 1110M Available.  In both cases, there is exactly 500 MB difference.  Where did this difference come from - and can I reclaim it?  Here is also lsof | grep 'deleted' - can't see nothing suspicious here:  $ lsof | grep 'deleted' nautilus  1911 user   21u      REG        8,5   142760     260562 /home/user/.local/share/gvfs-metadata/home (deleted) nautilus  1911 user   22w      REG        8,5    32768     268807 /home/user/.local/share/gvfs-metadata/home-fe882154.log (deleted) python    1919 user    8u      REG        8,5     4096     392258 /tmp/ffiqRK968 (deleted) python    2165 user    5w      REG        8,5        0     132261 /home/user/.[SNIP].lock (deleted) python    2166 user    5w      REG        8,5        0     132261 /home/user/.[SNIP].lock (deleted) python    2185 user   21r      REG        8,5   142760     260562 /home/user/.local/share/gvfs-metadata/home (deleted) python    2185 user   22r      REG        8,5    32768     268807 /home/user/.local/share/gvfs-metadata/home-fe882154.log (deleted) gnome-ter 2279 user   27u      REG        8,5      640     392575 /tmp/vte5KDX2X (deleted) gnome-ter 2279 user   28u      REG        8,5     4936     392605 /tmp/vteKRDX2X (deleted) gnome-ter 2279 user   29u      REG        8,5      648     392947 /tmp/vteMZDX2X (deleted) ubuntuone 2544 user   17u      REG        8,5     4096     392335 /tmp/ffiMErq0V (deleted) bamfdaemo 3235 user   12r      REG        8,5   143868     269077 /home/user/.local/share/gvfs-metadata/root (deleted) bamfdaemo 3235 user   13r      REG        8,5    32768     272310 /home/user/.local/share/gvfs-metadata/root-18092a02.log (deleted) firefox   5291 user   59u      REG        8,5    33288     132262 /var/tmp/etilqs_YdeZiWSd5iQwJ4U (deleted) firefox   5291 user   60w      REG        8,5    32768     132271 /var/tmp/etilqs_MNLXhEaEqoXMm9b (deleted) firefox   5291 user   70u      REG        8,5    34952     132297 /var/tmp/etilqs_yXDdwVeMxmmdpNz (deleted) I'm taking Calculus II next semester so I don't have all the tools from it to back me up but something came up in a discussion this evening that asked me to prove that the following sequence converges. As I'm new to formal math I'm hoping someone can verify my proof, especially step $6$. I must prove that $$\lim_{n\to\infty}P_n=b$$ where $$P_{n+1} = P_n + \frac{b-P_n}{2}$$ $$P_0 = a$$ and $a,b \in \mathbb{R}$ such that $a&gt;b$ My proof goes as follows:   We must prove that $$\lim_{n\to\infty}P_n=b$$  That is, $\forall\epsilon&gt;0$ there exists a $\delta$ such that there exists an $n$ satisfying $$n&gt;\delta \iff b-P_n&lt;\epsilon$$  First, let us prove that $P_n$ is bounded by $b$ by contradiction. Let us choose an $i$ such that $P_i &lt; b$ and $P_{i+1}&gt;b$. Then we have $P_{i+1} = P_i + \Delta P$ where $\Delta P &gt; b-P_i$. but this is impossible because by the definition of the recurrence $\Delta P = \frac{b-P_i}{2} &lt; b-P_i$. Therefore, $P_i$ is bounded from above by $b$.  Additionally, it is trivial to show that $P_{i+1} &gt; P_i$.  With this in mind, choose an arbitrary $\epsilon$. We need to show that there exists an $n$ such that $P_n &gt; b-\epsilon$. Assume the contrary, that $P_n$ is bounded by $\epsilon$.  Using a similar argument to what which was used before, assume $P_n$ is bounded by $\epsilon$ and then there exists a $P_i$ such that $P_{i+1}\not &gt; P_i$. But this results in a contradiction with (4)  Therefore, $P_n$ is not bounded by $\epsilon$ and we have proved what we want to prove. Use abbreviations for 1000+ score in linked posts I don't really enjoy the ragged view of linked posts:    This feature request is to use a format that suggested in ; something that matches the user-profile tags page in terms of the tally:    That is, use abbreviations for 1000+ (k for 1,000+, m for 1,000,000+, ...). RegEx match open tags except XHTML self-contained tags For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements? Speak Slower or Speak Slowlier? AFAIK the correct grammar for "speak slow" is "speak slowly" (slowly being an adverb). Please correct me if I am mistaken.  But in daily life I have not heard anyone saying "Speak slowlier".  I think I heard folks saying "Speak slower" but I also think it is incorrect.  Which is the best or correct form to convey the message?  Could that be the longish "Speak more slowly?" Changing order of features in shapefile Is there a tool to get the lines in one file that are not in another? How to stack three relations I have  $m\times n = n + n + \dots + n$    in my text right now, but I would like to put a curly brace under the \dots to emphasize that there are m,n's involved. How would I do this? Comparing integers: arithmetic expression or conditional expression In Bash, two integers can be compared using conditional expression     arg1 OP arg2      OP is one of -eq, -ne, -lt, -le, -gt, or -ge. These   arithmetic binary operators return true if arg1 is equal to, not equal   to, less than, less than or equal to, greater than, or greater than or   equal to arg2, respectively. Arg1 and arg2 may be positive or negative   integers.   or arithmetic expression:     &lt;= &gt;= &lt; &gt; comparison      == != equality and inequality   Why do we have two different ways for comparing two integers? When to use which?  For example, [[ 3 -lt 2 ]] uses conditional expression, and (( 3 &lt; 2 )) uses arithmetic expression. Both returns 0 when the comparison is true  When comparing two integers, can these two methods always be used interchangeably? If yes, why does Bash have two methods rather than one? Book about space alien cats I read a book when I was young, it was about space alien cats. I believe the title was Quzzles, but I really don't know. The book was stolen from me before I was finished. I don't know much else about it. Why does old PMOS/NMOS logic needed multiple voltages like  +5, -5, and +12 volts? For example, old Intel 8080 processors, old DRAMs, e.t.c...  I'm interested in the causes on the physical/layout level.  What was the purpose of these additional voltages?  Yes, this question is about stuff which was used 35 years ago.