Wikipedia:Reference desk/Archives/Computing/2011 February 22

= February 22 =

Network Traffic Monitor- Mac?
I need a utility (preferably free) that will allow me to monitor all the traffic on my network ie. sites that client machines are visiting, bandwidth i/o. I don't have the ability to install any software on the client machines themselves.

Suggestions?

Thanks in advance.

Perfect Proposal  00:25, 22 February 2011 (UTC)


 * Wireshark might do what you want, and it runs on OS X. Or you could install a proxy server, force all client machines to connect to it, and use it to log all traffic.  Or your router/firewall may have the ability to monitor connections, at least to measure bandwidth.  --Colapeninsula (talk) 11:22, 22 February 2011 (UTC)

images and videos
Earlier I posted this:
 * On my home computer, a old Dell machine running some version of MS Windows, probably about 20% of youtube videos are invisible to me---I just see a black screen where the video should be---although I can see them on other machines. In Wikipedia's article titled trigonometric functions, I can see the image whose caption begins with "The sine, tangent, and secant functions of an angle constructed geometrically in terms of a unit circle." but I can't see the one below it.  I can see its caption.  On all other machines I can see it.  Same for various other images in Wikipedia articles; I haven't kept a list.  Now I look at this page on facebook, and see a blank space where, with a machine in a library, I saw things I could click on and hear song excerpts.  There's also a blog where I posted a comment more than a year ago, where I can't reload the page (but can on other machines) and see only the page as it existed when I posted there.
 * What's going on? Michael Hardy (talk) 04:13, 5 February 2011 (UTC)
 * What's going on? Michael Hardy (talk) 04:13, 5 February 2011 (UTC)
 * What's going on? Michael Hardy (talk) 04:13, 5 February 2011 (UTC)

The response was that I should get an updated version of flash player. Implausible from where I'm sitting, but I did so, with no effect at all. Why this happens with such frequency with videos I've recently watched and so seldom with older videos isn't explained. But here's a new data point: A blogger posted a link to a youtube video. I watched it while looking at the blogger's web page. When I clicked on "watch on youtube", bringing up a separate browser window, I got the same blank white screen that I'd seen before. Then I went back to the blogger's page and I could still view the video. Michael Hardy (talk) 04:38, 22 February 2011 (UTC)


 * What happens when you try viewing the video using a different browser? I have seen certain websites where Internet Explorer 8 shows a big white rectangle for Flash content (including Flash videos, I think) whereas Mozilla Firefox shows the Flash content correctly.  Try using Firefox, Google Chrome, and IE, and see if the problem exists over all those browsers, and that may narrow down the problem.  (And it may shove you toward using a different browser if this magically fixes the issue for you.)  Comet Tuttle (talk) 19:47, 22 February 2011 (UTC)


 * (EC) It sounds like there may be several things going on. As far as seeing or not seeing certain images on Wikipedia, this might be resolved by clearing your browser's cache.  It might also be useful to completely clear the history and all cookies, although that might be overkill. It's possible that clearing the cache might resolve the issue for the videos as well, but it would also be helpful to know what browser and which version you are running, and if you have any add-ons, such as an ad or script blocker. Finally, you may want to run a cleanup and full error check on your hard drive; if your browser's cache is indeed becoming corrupt, it may be that the disk itself is having problems. -- LarryMac  | Talk  19:48, 22 February 2011 (UTC)

I've tried three different browsers, with identical results: internet explorer, firefox, and google chrome. Michael Hardy (talk) 16:32, 23 February 2011 (UTC)

Supercomputer
How do supercomputers use multiple motherboards? Would the same technique be practical for home use, so it would be possible to have multiple graphics cards, more RAM, multiple CPUs, etc.? --  T H F S W  (T · C · E) 05:16, 22 February 2011 (UTC)


 * The short answer is that several approaches have been used, with a greater or lesser emphasis on high speed communication between motherboards. You should understand that a particular computer architecture is usually best for a certain class of problem. Distributed computing describes large problems that can be divided in ways that allows them to be processed with large numbers of ordinary computers. One specific application is SETI@home. Jc3s5h (talk) 05:28, 22 February 2011 (UTC)


 * A supercomputer is basically a bunch of computers connected by a network (possibly a very fast one by network standards, but much slower than CPU <-> RAM speed). Supercomputers operate on embarrassingly parallel problems, generally, so that communication overhead between nodes isn't such a big deal.  Supercomputing techniques don't really apply to home computers because there aren't many desktop problems that require that level of parallelism.  The big exception is 3D graphics, and so a graphics card is basically a large number of simple processors operating together.  It's already possible to have more than one graphics card in a single computer, with no shenanigans. (I think I read about a multiple-graphics card laptop once, even.  It was large.)  Paul (Stansifer)


 * Of note - for many years, supercomputers, such as the Crays, used vector processors. You won't find vector processors in any home computers. The only way to get one that I know of is to get an old PS3 that lets you add a linux partition. But, you'll end up with no memory to work with, so the vector processor is basically useless. --  k a i n a w &trade; 15:52, 22 February 2011 (UTC)
 * You won't find super-computer sized vector processors at home - but inside most Pentium-class (and newer) desktop/laptop computers is SSE, which is sort of like a 4-element vector processor. And inside your graphics card, you might find a GPGPU that can be programmed as a vector processor; depending on your model, it may support in the neighborhood of 16 to 256 simultaneous SIMD (vector) operations.  Those are actually pretty big - larger than Cray 128-element vector hardware!  The largest "vector" system I am aware of is the Convey HC-1, which in 2010 was aiming for around 1024-element vector processing.  Nimur (talk) 16:03, 22 February 2011 (UTC)

To answer the original question, take a look at Beowulf (computing). This is the most straightforward way that you, as a home-user, can construct a "multi-motherboard supercomputer." If you start applying your compute resources to a particular problem with special needs, you might find that beowulf clusters have unsuitable performance - but for many types of computer problems, a cluster is faster than a single machine. Nimur (talk) 16:15, 22 February 2011 (UTC)


 * AFAIK, a supercomputer isn't actually a single computer at all (i.e. it does not have a single system image); it is a cluster of nodes, each of which is a computer in its own right. A Beowulf cluster is a computer cluster where all the nodes are identical, and the applications that are run on the cluster are tightly coupled. This is as opposed to a heterogenous cluster is one where the nodes are not identical to each other, the applications may or may not be tightly coupled, and embarrasingly parallel computations may be performed. (Although a Beowulf cluster is equally capable of performing embarassingly parallel computation.) In a computer cluster, all the nodes are linked by a high-bandwidth interconnect such as InfiniBand or 10Gb Ethernet, which is what permits high message-passing performance in clusters. Rocketshiporion ♫ 08:32, 23 February 2011 (UTC)

If you want to construct a Beowulf cluster at home, all you need are multiple identical PCs connected to an Ethernet switch, and a Networked-Attached Storage device. (I'm presuming that the PCs will boot locally, as otherwise you will a Storage Area Network, which gets more complicated). And you'll need a console switch to manage all the nodes from a single console. Rocketshiporion ♫ 08:37, 23 February 2011 (UTC)

Add own update sources in Microsoft Update?
Is it possiblt to extend Microsoft Update in Windows 7 by adding non-MS update sources? (like Firefox, for example) --91.4.234.221 (talk) 10:50, 22 February 2011 (UTC)


 * No. You can add MS Office, but that's it. FileHippo has an application update checker. -— Gadget850 (Ed)  talk 14:18, 22 February 2011 (UTC)
 * Or to be more precise, any Microsoft Products, devices installed on your computer that has new drivers that are pushed through Windows Update General Rommel (talk) 23:33, 22 February 2011 (UTC)

How to avoid any conflict between internal DVD drives
Currently my several-years-old WinXP SP3 computer has a DVD RW drive and a CD RW drive, both internal. I would like to replace the CD RW drive by a DVD ROM drive, so that I can make spare copies of my backup data disks.

What do I need to do regarding changing the jumper settings on the drives so that there will not be any conflict? Thanks 92.15.8.100 (talk) 13:25, 22 February 2011 (UTC)
 * You don't have to replace drives. Buy an external optical disc drive or use ImgBurn. Oda Mari (talk) 19:36, 22 February 2011 (UTC)
 * Oda Mari is correct; most or all DVD copying software lets you copy the contents of any non-copy-protected disc to an ISO file, and then you can swap discs and write the ISO file out to a blank DVD. Comet Tuttle (talk) 19:40, 22 February 2011 (UTC)
 * I don't have to get out of bed in the morning, but that does not answer the question either. 92.15.2.21 (talk) 21:40, 22 February 2011 (UTC)
 * Biting the volunteers offering help usually means they stop helping you, as has just occurred in this case. Comet Tuttle (talk) 19:13, 24 February 2011 (UTC)
 * If you insist on answering your own questions rather than the ones asked, then don't bother volunteering. 92.28.247.68 (talk) 00:06, 26 February 2011 (UTC)
 * If your drives are SATA drives, you don't have to perform any jumper setting changes. If they are PATA drives, on the same PATA bus (usually meaning that there is one data cable with 2 connectors, and each connector on the same cable is attached to a drive), then one of the drives needs to be set to "Master" and the other needs to be set to "Slave".  If they are PATA drives and are on different PATA buses, and nothing else is connected to the buses, then both need to be set to "Master".  All PATA drives that I've seen have a sticker on the drive itself telling you how to set the Master and Slave jumpers.  Comet Tuttle (talk) 19:38, 22 February 2011 (UTC)

Thay are the older PATA type, also called IDE I think, taken from another old computer, and there is no sticker to be seen.

Are jumper settings standardised? The drives have the same three possible jumper settings. Is there any standardisation over what the three positions mean? Thanks 92.15.2.21 (talk) 21:40, 22 February 2011 (UTC)

Making back-up DVD data disks secure
Is there any easy standard way of making DVD data disks used for backup secure, in other words they need a password to be supplied?

Past experience has taught me that wrapping everything up in a huge multi-GB password protected zip file is not the way to go. Is there any other way? Thanks 92.15.8.100 (talk) 13:33, 22 February 2011 (UTC)


 * You could put your files into a TrueCrypt container and then burn that to the DVD. TrueCrypt works like a virtual hard drive, but once you burn it to the disk it will be read only 82.43.92.41 (talk) 15:56, 22 February 2011 (UTC)
 * I, too, use TrueCrypt for this purpose, and in the same way 82 suggests. The disadvantage &mdash; and it's an annoying one sometimes &mdash; is that you do need to install TrueCrypt on any computer that wants to read the disc.  Comet Tuttle (talk) 19:43, 22 February 2011 (UTC)
 * You don't need to install it: Truecrypt can be run in portable mode, though you still need administrator privileges. Presumably, you could just put the Truecrypt program files on the DVD, and run it right from that (though I've never tried it, so no guarantees). Buddy431 (talk) 03:35, 23 February 2011 (UTC)


 * I believe that I know just what you're looking for - Imation Defender Optical Media. Rocketshiporion ♫ 09:04, 24 February 2011 (UTC)

Fault tolerant files from extra redundancy
Are there any standard ways of creating files that have extra fault-tolerant redundancy built in, so that they are still readable even if they were, for example, copied to a writeable DVD disc with errors? Thanks 92.15.8.100 (talk) 13:37, 22 February 2011 (UTC)


 * In your example, DVD errors would make it rather impossible to read the file regardless of redundancy due to how CDs and DVDs work. Once an error is located, there is a very weak attempt to continue further. Usually, that attempt fails and you only get the file up to the error. On the other hand, if you are referring to nothing more than a flip of 1s and 0s for some strange reason, error correction codes have existed for many years because they were necessary for older telephone communications. -- k a i n a w &trade; 15:49, 22 February 2011 (UTC)
 * Giving up after encountering a single read error is a feature of file copying programs, not CDs or DVDs. There is file recovery software that will skip over bad blocks and read the rest of the file. (I can't name any specific examples, never having needed such a thing myself). CDs and DVDs have extensive error recovery built in (using Reed-Solomon codes, mentioned below). That won't help if the error was introduced while burning the file, but you can guard against that simply by verifying after every burn (and it's very unlikely to happen anyway). I was also going to mention Par files, but it looks like someone beat me to it. -- BenRG (talk) 08:03, 23 February 2011 (UTC)


 * Well, I don't know if this is a "standard", but it's obvious: Write 100 copies of the file to the DVD.  This would provide a lot of redundancy, and if you get an error reading a file, just read a different copy of the file.  You could still get stuck in the case of errors in the directory structure or related structures, which would then require you to use some sort of undelete software that works on DVDs to scan the disk surface, and find and extract one of the undamaged copies.  You could then get a little fancy to deal with the situation where you somehow get several copies of the file from the DVD but their contents differ; you could write a little batch file using the Windows fc command to compare the various versions of the file you have, and implement some kind of voting system to figure out which version is "authentic" ... but I think DVD error detection/correction is good enough to give you a read error rather than bad bits when you try to copy a file from the DVD.  Anyway, I am in the habit of doing this when I back stuff up to DVD and there's extra space on the DVD; but I must say that I can't remember my stratagem ever actually coming in handy.  Comet Tuttle (talk) 19:33, 22 February 2011 (UTC)

So the short answer is "No". Pity. Thanks 92.15.2.21 (talk) 21:41, 22 February 2011 (UTC)


 * You might be interested to learn about Reed–Solomon error correction. Marnanel (talk) 22:40, 22 February 2011 (UTC)


 * Don't count on any internal redundancy to deal with media errors. If the whole disk fails (which can happen), it doesn't matter how redundant it is.  It's much better to have another copy on a different disk than to have a thousand copies on the same disk.  Paul (Stansifer) 02:18, 23 February 2011 (UTC)


 * I think you are asking for Par files. 71.141.88.54 (talk) 07:49, 23 February 2011 (UTC)

Thanks, although from reading the link and its links, it looks like it needs to mature some more before it becomes reliable and trustworthy. 92.29.115.56 (talk) 10:46, 23 February 2011 (UTC)


 * You can add ECC files like ICE ECC (I find it better in numerous ways but it's not opensource or even that popular so there's a risk 5-10 years down the track your parity files will be fairly useless if the program to use them doesn't work on your computer) or as someone mentioned PAR2 (popular in some circles and opensource so probably not going to disappear although IMHO the format isn't as good as ICE ECC). BTW PAR files have existed for a very long time, little work is being done on them, so they're not likely to 'mature' in any way. If you're specifically referring to optical media, try DVDisaster . However bear in mind what someone else already said, if the whole disc fails, or you simply lose it, you'll still lose data so these steps should only be used in addition to extra physically/geographically seperated backups if you really care about the data. Nil Einne (talk) 13:42, 23 February 2011 (UTC)

Thanks, DVDisaster looks interesting. The achille's heel of discs would I suppose be the directory structure, since there is only one copy of it. Unless no directory structure is required for a simple file at the root of the disc? That file could be a zip file with a directory structure within it. 92.24.188.45 (talk) 18:08, 25 February 2011 (UTC)


 * Are you referring to DVDisaster? If so, it includes ECC data for the entire image which of course includes the directory structure (and any other metadata) so there's no achilles heel there. In fact it's one of the reasons why dvdisaster is probably better on optical media then ICE ECC or Par2 files. When trying to recover it simply reads sector by sector and can recompose the image if there's sufficient recovery sectors for what's damaged. The achilles heel would be if the disc is so badly damaged that the recovery info isn't enough or that it's not even recognised by the drive (e.g. leadin is damaged) so can't be read at all. One disadvantage is RS03 the new codec which is designed to be multithreadable is still in testing stages so probably isn't recommended for production work and while it doesn't take that long to create recovery data even on a single core for a DVD, interest in RS01/RS02 may fade over time so it may be difficult to get them to work on future computers. On the other hand some speculate optical media is at a dead end anyway Nil Einne (talk) 19:29, 27 February 2011 (UTC)

batch files
Is it possible to make a .bat file run all .bat files in another folder one by one? The idea would be to have a folder of .bat files which do various things, and only need to start one .bat to make them all run, and if I add or remove any of the .bat files the script won't need editing 82.43.92.41 (talk) 15:55, 22 February 2011 (UTC)


 * Something very much like this should work (caution: untested):
 * for %%i in ( c:\myhome\mybats\*.bat ) do call %%i
 * 93.95.251.162 (talk) 16:43, 22 February 2011 (UTC) Martin.

How to copy a nonprotected, noncommercial DVD
I urgently need to copy a DVD someone recorded with their camcorder. It is not a commercial recording and has no copy protection. I cannot find any DVD copying capability in the various programs on my PC which seem related to media. Googling "DVD copying" just leads to discussions of how to defeat copy protection by buying some expensive program. What program I already have, or what reputable freeware program, would allow me to make a copy of a DVD? I have Express Burn, Windows Movie Maker, Windows Media Center, Windows Media Player, RealPlayer SP, Itunes, Replay AV 8, and Quicktime. Thanks. Edison (talk) 16:25, 22 February 2011 (UTC)
 * imgburn can save an iso image of the DVD onto your hard drive. You can then burn that back onto a new DVD download 82.43.92.41 (talk) 16:37, 22 February 2011 (UTC)
 * What is an "ISO image?" Which of the programs listed would do the burn, or would imgburn? It looks like I can upgrade to Realplay Sp Plus and burn a DVD. Its just surprising that a basic DVD burn capability does not come with the PC when they include a DVD burner drive. Edison (talk) 16:43, 22 February 2011 (UTC)
 * imgburn will do both. An iso image is an exact copy of the original dvd contained into a file. When you burn the iso image to the new dvd, make sure to select the right mode otherwise it will burn the actual iso file instead of making a duplicate of the original disk. Also make sure you have enough hard drive space before you begin; for a dvd you will need about 4GB 82.43.92.41 (talk) 16:49, 22 February 2011 (UTC)
 * Thanks. Express Burn claims to have the capability to save an ISO and burn a DVD from an ISO,although the DVD it creates will not play on a DVD player, a fact which has been noted in online forums. It does not say how it is saving it (file name, folder).  Is it likely to save the ISO file as an internal working file and then delete it automatically, or is user action typically required to get rid of the disc clutter after a copying project? I hate to think of all that hard drive devoted to a copy of a files used briefly, as permanent clutter. How would I search to see if the ISO file is still on the hard drive? Edison (talk) 17:44, 22 February 2011 (UTC)
 * How about this one? Oda Mari (talk) 18:31, 22 February 2011 (UTC)
 * I was successful with Imgburn. Way better than Express Burn, since not only did it clearly state where it was saving the iso file, but the copy DVD actually played on a normal DVD player. Thanks! Edison (talk) 19:08, 22 February 2011 (UTC)


 * I prefer CDBurnerXP to ImgBurn. Despite its name it also does DVDs. 92.15.2.21 (talk) 23:41, 22 February 2011 (UTC)
 * The amazing and gratifying thing for me is to get a computer to actually do something useful. Edison (talk) 05:23, 23 February 2011 (UTC)

Firefox Not Responding
Hello everyone!

I need help of you people,i have a very strange problem in firefox 3.613,when i am browsing the net it stop working for a few seconds and

then works again.Mouse and keyboard doesnot work during this time.this problem is with only firefox i have installed windows 7 and i have a few

plugins also installed.Any help will be appreciated.Thank You! —Preceding unsigned comment added by 119.154.116.124 (talk) 18:41, 22 February 2011 (UTC)


 * Without knowing which websites you are visiting, I have to assume you are experiencing the normal lockup while waiting for flash-based ads to load. -- k a i n a w &trade; 18:45, 22 February 2011 (UTC)

Upload Image to replace old one
This is a question about using Wikipedia, moving to the help desk. The question is now available at Help desk. J I P &#124; Talk 19:50, 22 February 2011 (UTC)

What is the name for a word...
... that only returns a single result when it is searched with Google or another search engine? I dimly remember that searches for this kind of (real-life?) words is a kind of contest and that those words even got a specific name that has possibly an entry on Wikipedia, but I do not recall any more details... Does my description say anything to anyone? regards, Grand-Duc (talk) 20:35, 22 February 2011 (UTC)


 * Are you referring to googlewhack? -- k a i n a w &trade; 20:38, 22 February 2011 (UTC)


 * Yeah, that looks good, thank you! :-) Grand-Duc (talk) 20:40, 22 February 2011 (UTC)


 * How about "hapax legooooomenon"? -- BenRG (talk) 10:43, 23 February 2011 (UTC)

Question on mobile format on iPad
when i first got my iPad a month ago all of the wikipedia pages came up in mobile format. I noticed within the last couple of days it changed to full page format. If I prefer the mobile, how can I get pages to display that way? Lastly, do you know why it changed to full version without asking me? By the way I tried your help desks live chat and they recommended I ask the question here. Thanks for helping me!98.255.194.166 (talk) —Preceding undated comment added 21:34, 22 February 2011 (UTC).
 * I Know you are all busy but if someone could help me. I would appreciate t!98.255.194.166 (talk) —Preceding undated comment added 22:03, 23 February 2011 (UTC).


 * Just change the URL from en.wikipedia.org/... to en.m.wikipedia.org/... --Sean 00:55, 24 February 2011 (UTC)

Would I have to do that every time I open a wikipedia page or is there a way to make the iPad default to mobile pages? When I first got the iPad it was doing that automatically98.255.194.166 (talk) —Preceding undated comment added 15:51, 24 February 2011 (UTC).

javascript
Do the date and time functions in greasemonkeys javascript on firefox conform to the timezone of the computer it's run on, or does it use something else like UTC so it's standard across any computer? For example; String((new Date).getTime).replace(/\D/gi,'') 82.43.92.41 (talk) 22:25, 22 February 2011 (UTC)


 * getTime returns Unix time, which is independent of timezone. Some of the other functions in the Date class return local time (such as getHours) and some return UTC (such as getUTCHours). Marnanel (talk) 22:34, 22 February 2011 (UTC)