Wikipedia:Reference desk/Archives/Computing/2011 December 28

= December 28 =

I've had enough of this bullshit
Pardon the language, but right now I am typing this with the utmost frustration. My computer keeps self-hibernating/going in stand-by mode without warning ALL THE DAMN TIME. And it's becoming more and more frequent. Restarting it no longer keeps the problem at bay, I have to continuously restart the PC literally every five minutes. I have reliable anti-virus software installed, and nothing suspicious comes up, so I don't know what the fuck is going on. I'm on Windows 7, and I've never had this problem with previous PCs or operating systems, even when they were chock full of viruses at times. I'm not overtaxing the system or anything. So what is this? 76.64.255.81 (talk) 00:18, 28 December 2011 (UTC)


 * You may well get a nice technical answer to this question, but I had something very similar recently that had a rather simple solution. My monitor sits on top a couple of rack units, on which are a number of switches and knobs.  One of these knobs lines up EXACTLY (both horizontally and vertically) with the "sleep" button on my keyboard.  If the keyboard is pushed too far into the desk, *boom* – the computer goes off, no warning.  I've removed the knob (I don't use it) so I no longer have this problem.  matt (talk) 01:49, 28 December 2011 (UTC)


 * Never mind, I got some tech help and the source behind the issue is so much deeper than I expected and completely unforeseen. I'm gonna have to get a new computer altogether. 76.64.255.81 (talk) 01:53, 28 December 2011 (UTC)


 * OK, I'm all curious now. Hardware or software fault? HiLo48 (talk) 02:15, 28 December 2011 (UTC)


 * Since I didn't buy the computer myself and don't know from where it was bought, I've been told that I may have gotten screwed and that the computer is running a version of Windows it isn't supposed to, and that it's a pretty old model. 76.64.255.81 (talk) 02:53, 28 December 2011 (UTC)


 * I have several older computers running software that's no longer supported. That doesn't mean you need to toss it out.  It's quite possible that your computer isn't up to running Windows 7, in which case Windows XP or Linux might be a good choice.  Did they tell you exactly why your computer can't run Windows 7 ?  Is it the amount of RAM, speed, or what ?  (You might be able to upgrade your computer to solve some problems.) StuRat (talk) 03:05, 28 December 2011 (UTC)
 * Well, one is that it doesn't have enough gigs to handle W7 (they told me that it's barely sufficient enough to run Vista), and there's the fact that it's running the Enterprise version of W7, which in itself set off red flags to the people I was explaining this to. 76.64.255.81 (talk) 03:56, 28 December 2011 (UTC)


 * Sounds a lot like it's overheating, in which case there's no need to replace the computer. As a workaround, get a powerful fan and aim it at the guts of the computer, with the case removed.  In the long run, perhaps you could replace the case fan and hard drive fan with more powerful ones. StuRat (talk) 02:29, 28 December 2011 (UTC)


 * Powerful fan = noise. Avoid noise if you want to get work done. Barely sufficient to run Vista? I'm surprised any IT would even dare mention Vista as an option nowadays. It is/was a hog compared to Widows 7. Dmcq (talk) 10:55, 28 December 2011 (UTC)


 * The noise issue depends on the person - I actually find that a bit of non-specific noise (as from a fan), or ambient music helps drown out other sounds (conversations in the street outside, aircraft overhead, dogs barking) that are far more likely to distract me. Equisetum (talk &#124; contributions) 14:50, 28 December 2011 (UTC)


 * The noise is far less annoying than a computer that goes down every 5 minutes. I agree that a computer than can't run Windows 7 shouldn't try to run Vista, either.  Go back to Windows XP, or, better yet, Linux. StuRat (talk) 20:10, 28 December 2011 (UTC)


 * It must be a very old computer if it is "barely sufficient enough to run Vista". Microsoft's minimum requirements for Vista were: 800 MHz processor, 512 MB RAM and 20 GB hard drive space, though I don't think Vista would run quickly on that configuration.  (I'm typing this on a one Gig machine and it runs Vista adequately.  I wouldn't want to run W7 on it, even though it meets the minimum requirements.)  Could you tell us the specification?  If it's just a very old computer with less than a Gigabyte of RAM, then StuRat's suggestion of Linux or XP might be the answer, or possibly just add some RAM, but if there is a faulty fan or processor then you ought to replace this (or the computer).  Another possibility is a faulty power supply.    D b f i r s   23:04, 28 December 2011 (UTC)


 * We need more feedback to answer this properly. As Stu suggested it might be over heating. It is easy to take the side off and look at the heat sink on the CPU. Is it covered with fluff? If so, then this need to be removed as it will coarse the chip to overheat and shut down. On a old computer this is one the  first things that ought to be checked. ---Is it covered with fluff?--Aspro (talk) 23:21, 28 December 2011 (UTC)


 * I apologize for replying so late (hopefully you guys will still care at this point). My computer is a Lenovo ThinkPad T61 7659. I am not sure exactly how many gigs mine has, but it seems that its maximum capacity is 2-3 gigs of RAM. And apparently, they usually come pre-installed with XP, Vista Business or Linux, so it's a great mystery to me as to how one would manage to get Windows 7 installed and running on it. And I've heard some unusual noises coming from the computer, which I guess is a result of overheating, but the weird behavior started months ago (not soon after I got the computer, which is refurbished) and have gotten progressively worse. 76.64.255.81 (talk) 11:07, 29 December 2011 (UTC)


 * I'm guessing that whoever put Win 7 on it also set it to overclock, causing it to overheat. Sounds like an idiot.  Can you tell us how you got such a messed up computer ?  StuRat (talk) 05:23, 30 December 2011 (UTC)


 * A friend of mine ordered it online on my behalf (the hard drive on my previous laptop gave up and died, so I was temporarily devoid of a computer), however they never told me where exactly they bought it from. I specifically requested a computer that runs Windows 7, but I obviously meant one that came preinstalled with the system. This wasn't even my computer of choice. Also, it runs without problems when I run it in Safe Mode. So hopefully, this is something that can be easily solved. Though I must ask, is it normal that system information isn't viewable in Safe Mode? 76.64.255.81 (talk) 07:13, 30 December 2011 (UTC)


 * No, system info should be viewable. What happens when you try ?  I'm afraid the person who told you it can't handle Windows 7 was right, from looking online it seems to come with either XP or Vista.  I certainly wouldn't recommend Vista, but XP should fly on that computer.  So, I recommend you "downgrade" to XP Pro, Service Pack 3.


 * The reason it's able to run in safe mode is that so much is disabled. You might be able to run in safe mode indefinitely, however, running XP would be a lot better than running Win 7 in safe mode.  BTW, Lenova might have put Win 7 on it themselves, so they could sell it.  Based on this review, they seem a rather dodgy company: . StuRat (talk) 22:11, 30 December 2011 (UTC)


 * That review response sounds like a dodgy importer of a faulty batch. I'd be worried if there were more like it.  Lenovo are the second largest computer maker by volume in the world  That doesn't mean that they make good machines, of course, but many people seem satisfied with the product. (Disclaimer: I've only ever used one Lenovo machine and I've no shares or interest in the company!)    D b f i r s   22:01, 1 January 2012 (UTC)


 * Unfortunately, the OP may have gotten one from the same bad batch. StuRat (talk) 00:29, 2 January 2012 (UTC)

Running in safe mode indefinitely isn't a viable option for the long run, as I'm rather limited in what I can do in safe mode. Anytime I try to view system info in "My Computer", it tells me that it isn't available. I at first thought it meant that my copy of Windows 7 was pirated, but then realized that can't be it since the Validation Tool recognizes it as a genuine copy. Ah well, guess my only option for now is to downgrade to XP until I can buy myself a decent computer that won't give me so many headaches like this one. Thank you for your patience and advice, everyone. 76.64.255.81 (talk) 04:37, 31 December 2011 (UTC)


 * You're welcome, and good luck. I will mark this question resolved. StuRat (talk) 04:40, 31 December 2011 (UTC)


 * As a long-time user of several used Thinkpads I'd like to point out that in general T61 is still a perfectly good and usable computer. In this particular case it does sound like the hardware is faulty.  Another possibility is that the seller didn't do the Windows 7 installation properly, e.g. the BIOS version may be too old to support Windows 7.  Lenovo supports Windows 7 upgrades of many older models, including T61, by offering all the necessary hardware drivers and BIOS updates [for download].  There are also user guides, upgrade guides and hardware manuals on the support site.  But if your hardware is faulty, it may be the best solution to offer it on ebay as a faulty unit - there are hobbyists buying even broken Thinkpads in order to build working computers from parts.  188.117.11.111 (talk) 09:33, 31 December 2011 (UTC)


 * I thought of something else to add, too. I suggest you put Linux on it first, since that's free, and will allow you to be sure it will run OK once you stop using Win 7.  If it passes the test, then you can pay for XP.  If it hibernates every 5 minutes under Linux, then there is a deeper issue than just Win 7 being unsupported on it. StuRat (talk) 16:40, 31 December 2011 (UTC)
 * I do have an actual reference for Windows 7 support on T61 (besides the fact that Windows 7 drivers for T61 are available for download): [Here] is the list of Thinkpad models which can be upgraded to Windows 7 according to Lenovo. 188.117.11.111 (talk) 10:58, 1 January 2012 (UTC)

Where else is startup stuff?
At my workplace, mostly PCs, there's a local startup script that runs at each user logon, to unmount and remount the network drive, giving me an N: drive. (I think I know this because the black  box opens and closes.)  I'd like to chase down this script and look at it, but have been unable to find it. I'm thinking the script is NOT on the file server (how could I access it before it was accessible?), so it must be on my local disk -- somewhere.


 * I've scanned for .bat and .txt files, and for the text string "mount", to no avail.
 * There's nothing recognisable in All Users -> Programs -> Startup.
 * I've dumped the registry to text and searched for "mount", which found an instance of mountvol.exe, but that doesn't seem to have any paths in it and it's part of NLS Languages something.

Can anybody volunteer other suggestions for (a) What should I look for, and/or (b) Where should I look for it? My system is WinXP sp3.

Thanx! --DaHorsesMouth (talk) 01:29, 28 December 2011 (UTC)
 * Log on scripts I believe are usually *.vbs files. Default location for log on scripts is %SystemRoot%\System32\Repl\Import\Scripts. However if you are logging onto a domain, your computer might not have local scripts, they might instead be in Sysvol\DomainName\Scripts. Also, "mount" is not the command to map a network drive on windows, I think that is usually done with "NET USE". Lastly, I work in IT Support and advice you DO NOT to stuff around with your production log on scripts, it's probably against your IT policy to do so. If you have a problem or requirement which is not being met, talk to your IT support or manager. Vespine (talk) 05:44, 28 December 2011 (UTC)


 * If your system is part of a Windows domain (in other words, if your organization's system-adminstrator set up a centralized administrative server for all the Windows computers), then before your system even allows a user to log in, Windows is already running whatever the domain policy is configured to run. You can read more: Group Policy from MSDN TechNet.  "Group Policy provides an infrastructure for centralized configuration management of the operating system and applications that run on the operating system."  In other words, you are, in this case, entirely at the mercy of the system-administrator.  Your computer might not have permission to view all of the startup scripts that the domain administrator is running for you.  Nimur (talk) 20:21, 28 December 2011 (UTC)

Renaming Tabs in Excel 2007
How do I do that? Cheers! KägeTorä - (影虎) ( TALK )  01:31, 28 December 2011 (UTC)
 * In Excel 2008, I right-click on the tab and select rename. I'd guess it probably works similarly in Excel 2007.  RudolfRed (talk) 02:31, 28 December 2011 (UTC)
 * I have Excel 2007, and that is indeed the case. Buddy431 (talk) 18:09, 29 December 2011 (UTC)

Speed up XP
How to thank all who offered a variety of solutions to my question. Let it stand that I do thank them, and appreciate the time they took.

Hamish 84 Hamish84 (talk) 01:44, 28 December 2011 (UTC)


 * You could best thank us by telling us what suggestions you took and how much each helped to speed things up. Thanks. StuRat (talk) 02:33, 28 December 2011 (UTC)

Mobile Telecommunication ( IMSI / MSISDN )
1. What happens when same MSISDN is mapped to two different IMSI in a network ? If a subscriber calls this MSISDN will the call be routed to both these IMSI's ?

Kumar.saurabh90 (talk) 10:14, 28 December 2011 (UTC)

IM contacts
Rather a newbie when it comes to talking to people online, if someone asks for my MSN or YIM contact details, would that be the same as the email address that came with my Yahoo account and my windows live email address? As in [whatever]@yahoo.com and [whatever]@live.co.uk?

Also, whiilst I'm here, is there any way of copying something from my photobucket account to upload onto, for example, youtube, if the original is saved on a different computer?

79.66.106.204 (talk) 11:58, 28 December 2011 (UTC)
 * When I use to use Yahoo messenger, my instant messenger name was ctjf83 and my email was ctjf83@yahoo.com. So if they are asking for the name to contact you on messenger with, I'd just tell them your screen name minus @yahoo.com or @msn.com. I can't help you on the other question. C T J F 8 3  12:43, 28 December 2011 (UTC)

Listen to cell phone/MP3 on radio
Is there such a device that I can plug into my cell phone or MP3 player's headphone jack and then play the music through the radio, wirelessly? How does it compare to the headphone jack to tape thing? C T J F 8 3 12:29, 28 December 2011 (UTC)
 * They certainly exist - see e.g. this amazon search, and our article on them here. I haven't used one for a long time though (my current car stereo has an auxiliary port) and have never used a tape adaptor - so I couldn't tell you how well the ones out now work, or how they work in comparison to the tape thingy. My recollection is that they worked acceptably in my (rural) area, but weren't free from hassle (selecting a clear frequency) or interference issues. See the article for more details on limitations of these devices in large cities with lots of radio stations. You should also note that not all such devices are legal in all countries (depending on power, frequency range etc.). Equisetum (talk &#124; contributions) 14:44, 28 December 2011 (UTC)
 * Yes, they are sold for car radio reception in the UK, but they work fine in country areas, using a 12v portable battery and transmitting to a cheap radio receiver perhaps 20 or 30 yards away. The transmission frequency can be adjusted to a less-crowded part of the dial, but this might be difficult in some areas.  The quality is inferior to a direct connection from headphone jack to tape input because of the frequency modulation and demodulation involved, and quality can be much more seriously affected by poor reception and interference from other transmitters.    D b f i r s   16:21, 28 December 2011 (UTC)
 * Thanks, C T J F 8 3  22:01, 28 December 2011 (UTC)

Arabian hacker group
Hello. A couple days ago, I read about a group of Arabian hackers that exists to break down Arabian government restrictions on internet communication so citizens can communicate/revolutionize freely. I want to research this group for an essay, and tried googling "Arabian hackers" and couldn't find the group. Perhaps any of you know it? thanks!--SR-71 pilot (talk) 17:14, 28 December 2011 (UTC)


 * http://news.google.com/news?q=arab%20hackers ? ¦ Reisio (talk) 19:03, 28 December 2011 (UTC)
 * Yes, Telecomix was what I was looking for. thank you!--SR-71 pilot (talk) 00:08, 29 December 2011 (UTC)
 * Roger ¦ Reisio (talk) 21:22, 29 December 2011 (UTC)

Kindle Restart Problem
I am using Calibre to create collections. every thing works fine. All files get uploaded as they should. As you know to get the .mobi files in their proper collections (folders) one must RESTART Kindle. But I fail to get the "RESTART" option from the Menu ( It worked well yesterday ) One has to press MENU, select "settings" and then choose RESTART but I don't get to the "restart" it does not appear when I press "Menu" the SECOND time. The whole box that contains all options including RESTART, does not appear... Please help. Jon Ascton    (talk)  21:33, 28 December 2011 (UTC)


 * What model of Kindle are you talking about? On mine (a Kindle Keyboard) you do not need to restart for uploaded files to appear, if they are in the right directory. It takes a moment but the Kindle finds them automatically. I'm reasonably sure the Kindle Keyboard doesn't have a "restart" option, anyway. --Mr.98 (talk) 22:51, 28 December 2011 (UTC)


 * Thanks 98 for your response. Yes I have the one with a keyboard. It is not registered (am in India), so "make collections" is not working . The only way here to manage folders is by using the Calibre, which I have been doing successfully till now.As I write this..I have noticed two mysterious files (hidden) in Kindle folder, out of documents...can it be some new type of virus


 * Re: a virus, it seems unlikely to me. Maybe if you told us the file names, though, we could be helpful... --Mr.98 (talk) 00:23, 29 December 2011 (UTC)

Sum of digits of 2^1000
I'm trying to solve this problem which is to sum the digits in 2^1000. The obvious thing seems to be to just brute force it by working out 2^1000 (using big ints) and then suming the digits. However, I feel that that would be missing the point and think there may be a more clever way of doing it; perhaps based on the digits behaving in a predictable way every time they are multiplied by 2. I'd rather not get the full answer but if you could tell me whether I'm right or give me a hint otherwise. --178.208.197.58 (talk) 23:48, 28 December 2011 (UTC) UPDATE: I can see for example that every digit is doubled and then if it is greater than 10 you keep the least significant digit and add the most significant to the next one after it is doubled but then with everything you need to keep track of I feel it looks a lot similar to what would be done simply by using big ints --178.208.197.58 (talk) 23:54, 28 December 2011 (UTC)
 * This looks like a job for ... the Maths Desk! ;) 24.92.85.35 (talk) 00:35, 29 December 2011 (UTC)


 * Well, if the poster actually asks for a reduced sum of digits, then yes, it is a rather maths question. But the simple 'sum of digits' problem seems rather to be a test of programming skills – compare Google results for 'sum of digits of 2^1000' and 'reduced sum of digits of 2^1000'. --CiaPan (talk) 17:08, 29 December 2011 (UTC)


 * Lots of programs can do it in a millisecond but it's a big job to do by hand regardless of your algorithm. If you think there is supposed to be a "point" then are you sure the problem isn't about finding the digital root? The term digital sum is sometimes used about digital root. You wrote "sum the digits in 2^1000" and I don't see how that could be interpreted as digital root, but perhaps you paraphrased the original question? Finding the digital root by hand is quite easy with a suitable algorithm. PrimeHunter (talk) 02:19, 29 December 2011 (UTC)


 * "... there may be a more clever way of doing it ..." There is indeed a more clever way: unless the problem states otherwise, sum the binary digits (and of course be sure to give your answer in binary also). Mitch Ames (talk) 08:15, 29 December 2011 (UTC)


 * Maybe there is a clever way to do this. I'm not sure.  However, I've seen this and similar questions be used as a basic test of programming ability.  On platforms where there is no native support for big ints, the logic involved in exactly computing the decimal representation of 2^1000 can be seen a test of basic computational literacy.  Dragons flight (talk) 08:23, 29 December 2011 (UTC)


 * You could calculate 2^1024 much more easily by repeated squaring, and divide by 2^24. This may not be any quicker.  However, 2^1024 is a lot easier to calculate because you start with 2 and square it 9 times.
 * Or you could convert 1000 into binary, use this to factorise 2^1000 into a product of numbers of the form 2^(2^n), calculate the factors by repeated squaring, and multiply them all together; if you save intermediate values this will take about 14 large multiplications. --Colapeninsula (talk) 16:10, 29 December 2011 (UTC)


 * Look at the following table. (Sorry about the formatting. There must be an easier way.)
 * {| class=wikitable style="background-color:black"

! n !! 2^n !! Sum of digits !! Digital root
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |0	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |3	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |16	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |32	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |6	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |64	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |10	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |128	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |11	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |256	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |13	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |9	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |512	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |10	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1024	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |11	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2048	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |12	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4096	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |13	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8192	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |16384	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |22	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |15	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |32768	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |26	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |16	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |65536	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |25	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |17	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |131072	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |18	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |262144	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |524288	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |29	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1048576	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |31	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * }
 * Does anyone know if this pattern (if I didn't make any mistakes) continues indefinitely, and if so, whether this is a well known result?
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |11	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2048	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |12	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4096	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |13	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8192	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |16384	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |22	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |15	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |32768	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |26	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |8
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |16	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |65536	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |25	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |7
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |17	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |131072	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |18	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |262144	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |524288	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |29	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1048576	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |31	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * }
 * Does anyone know if this pattern (if I didn't make any mistakes) continues indefinitely, and if so, whether this is a well known result?
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |17	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |131072	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |14	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |5
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |18	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |262144	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |19	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |524288	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |29	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |2
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1048576	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |31	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * }
 * Does anyone know if this pattern (if I didn't make any mistakes) continues indefinitely, and if so, whether this is a well known result?
 * style = "text-align:right; background-color:#e6e6e6; padding:5px;" |20	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |1048576	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |31	|| style = "text-align:right; background-color:#e6e6e6; padding:5px;" |4
 * }
 * Does anyone know if this pattern (if I didn't make any mistakes) continues indefinitely, and if so, whether this is a well known result?


 * On Physics Forum the same question was asked and answered. "[For] the single digit reduced sum &hellip; work modulo 9 to get the answer (which is 7 btw)." So perhaps this is trivial.


 * RussAbbott (talk) 00:39, 30 December 2011 (UTC)
 * Your last column needs to be the digital root (so you keep summing the digits until you get to just one digit), but then the pattern will continue. It's a well known result (which is mentioned in the lede of that article) that the digital root of a sum is the sum of the digital roots of the summands (ie. digroot(a+b)=digroot(a)+digroot(b)). Setting a=b gives you digroot(2a)=2*digroot(a) (you may need to sum the digits of the RHS one more time after the doubling). In your table, the first column just doubles each time so the last column also doubles each time (with the digits being summed where necessary). Since the last column cycles once, it must continue to cycle forever. This is, in fact, the fourth bullet point in this list: Digital_root. --Tango (talk) 00:42, 30 December 2011 (UTC)
 * Thanks. Didn't realize what "digital root" meant. RussAbbott (talk) 00:59, 30 December 2011 (UTC)


 * The "sum of digits" column is A001370. -- BenRG (talk) 21:39, 2 January 2012 (UTC)

Hard Drive Performance Planning
I am likely to build a new high-end workstation this spring. I need significant amounts of data storage, though I would also like to see good performance. Currently I run a system with a 120 GB SSD for OS / software and a 2 TB RAID 1 for data. This is supplemented with a 6 TB NAS (RAID 5) for backups and long-term storage. I'm wondering what I should be thinking about for the next iteration. A particularly interesting possibility seems to be using an SSD cache to accelerate larger drive(s), e.g., or some form of small hybrid array. I know that Intel put SSD caching into their Z68 chipset, but I am unlikely to use that platform, so I am more likely to consider third-party solutions such as those offered by OCZ or some RAID controller manufacturers. I am wondering whether people here have experience with technology like this and what people might suggest using for cost-effective high performance disk storage in the near future. Dragons flight (talk) 23:51, 28 December 2011 (UTC)


 * Whether an SSD, or more RAM, will help performance is mostly down to the locality characteristics of your access to the data; if it's highly local it'll help, if it's random then it won't. RAID is not a backup - what's the actual size of a dataset, how valuable is it, and what have you thought about for real backup? Testovergian (talk) 00:06, 29 December 2011 (UTC)


 * As I mentioned, I have a NAS used to store real backups (in addition to offsite storage of the most valuable subset). This is not a question about backups, but rather about local storage performance.  Like most things, some data will be accessed relatively frequently while other data is accessed rarely.  The access patterns change week to week and month to month and so it is not so easy to plan for, but might respond well to caching platforms that are responsive to changing access patterns.  Dragons flight (talk) 00:47, 29 December 2011 (UTC)