Wikipedia:Reference desk/Archives/Computing/2011 October 11

Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 11

ipod touch to iphone adapter

Is there a case/cover that an ipod touch 4 can be placed into to make it the size dimensions of an iphone 4? I ask because there are several cases/covers that are only available in size for the iphone. I would use such a case like an adapter to put my ipod touch into, and then that combination into an iphone case/cover — Preceding unsigned comment added by 72.175.132.243 (talk) 05:03, 11 October 2011 (UTC)

Wouldn't be that time consuming or expensive to make your own: http://www.david-laserscanner.com/ http://www.shapeways.com/. Could probably manage around $30 for video camera ($10 actually you can use your iPod Touch's camera), laser pointer ($5-10), and shapeways materials (silly cheap). ¦ Reisio (talk) 19:26, 11 October 2011 (UTC)

Is it a violation when using marks over vowels in the English alphabet?

These days I read the pages "My Thuan Bridge" and "Can Tho Bridge" (which are two bridges recently built in Viet Nam). I read the articles/pages under the option "English" (not "Vietnamese" language) but in the English language, the articles/pages contain marks over vowels of the Vietnamese language (which the English alphabet does not have). For instance, in the English language, I can only write "Can Tho bridge" or "cau Can Tho" (the English word "bridge" means "cau" in the Vietnamese language) because ASCII does not let me type mark over the vowel "a" in the Vietnamese word "cau". However, in the pages "My Thuan Bridge" and "Can Tho Bridge", I think the writer(s) used VIETSCII to put marks over vowels although these marks over vowels are not used in the English language. Therefore, is it a violation when adding marks over vowels in the English alphabet?64.68.169.46 (talk) 19:27, 11 October 2011 (UTC)

No it would not be considered improper - there are quite a few English words with diacritics. Mostly they are loanwords and will have variant spellings without diacritics, but there are exceptions. In any case, foreign proper nouns such as those you mention would be expected to retain whatever diacritics they have according to the source language or transliteration system. Finally, I've not heard of VIETSCII - on Wikipedia (actually in most places these days) such symbols are produced using Unicode, which is far more comprehensive than ASCII. AJCham 19:47, 11 October 2011 (UTC)

Addition: I've been jumping between the ref desk categories, and was under the mistaken impression I was on the language desk. In answering the question I intepreted "violation" to mean improper use of English - I'm not sure what you mean by violation in a computing context. Sorry! AJCham 19:53, 11 October 2011 (UTC)

To take Mỹ Thuận Bridge as an example, presumably the only word that translates directly to English, "bridge", has been translated, and the order has been changed to reflect English grammar. "Mỹ Thuận" as presumably a name is fine rendered that way here, as long as it isn't known more popularly by another name to English speakers. ¦ Reisio (talk) 19:50, 11 October 2011 (UTC)

See Wikipedia:DIACRITICS for the Wikipedia Manual of Style entry on this. The general policy is "do what other sources in English do, and use your judgment." --Mr.98 (talk) 21:10, 11 October 2011 (UTC)

(And to redirect from the diacritic-less version, so that people can find it easily. Redirects are so freaking cool. Paul (Stansifer) 01:45, 12 October 2011 (UTC))

I'd respectfully suggest that diereses can be used in literate English, although they are uncommon. The New Yorker magazine's articles are painstakingly proofread, and I assume that there's a commensurate conern for details such as these. I've seen "coöperate" and (probably) "naïve", although the latter might be a relatively-recent import into English. However, using diacritical marks as decorations in text that's other than whimsical, I would say, is being sub-literate.

Regards,Nikevich (talk) 08:39, 13 October 2011 (UTC)

is there a limit on useful drives in raids?

I know that if you set up a raid with two hard drives and use that as your system drive your computer performance will increase a measurable amount. I am wondering if theres is an upper cap for number of hard drives in a raid before you stop improving performance. What im trying to ask is; will i get the same amount of performance in a 100 drive raid as in a 200 drive raid? Does hard drive speed affect this cap? The reason im asking is because i would like to build a gaming computer with 12 10,000RPM drives in a raid 0 (dont talk to me about fault tolerance, its a gaming machine and nothing important would be lost should a drive fail) and im wondering if 12 drives would be too much. – Elliott(Talk|Cont)  21:24, 11 October 2011 (UTC)

Yes there will be limits to the practical utility of a large RAID, but first it might be helpful to tell us what kind of hardware you intend to use to create the RAID. Many boards won't support 12 drives, and even if you can support that number the nature of the RAID controller can make a significant difference in the performance of a large RAID. Also, the nature of your workload (e.g. games) will make a difference. Large RAIDs are most useful when the amount of data being read to and from disk is very large. Dragons flight (talk) 23:47, 11 October 2011 (UTC)

A large factor in perceived performance of fixed drives is seek latency. RAID 0 either cannot improve (except under rare and unusual circumstances, possibly), and can slightly decrease it. You might be using a single SSD. Paul (Stansifer) 02:12, 12 October 2011 (UTC)

@Dragons flight I was originally planning on using 12 drives in a raid but i have been unsuccessful in my efforts to find an affordable raid controller for that many so i might just be using half that, 6 drives. As for the nature of my work load, it would be mostly gaming, but my system as it is (2 drives in raid 0 on a MSI k9n sli) works just fine for that, no its not the work load that makes me want to build a massively powerful gaming computer, its that i want to know that i am using something at its maximum potential. Which is why i originally asked: Is there a set number of drives that raid 0 can handle before performance stops increasing? – Elliott(Talk|Cont)  05:12, 12 October 2011 (UTC)

The typical interface chips for a good consumer system can in principle write / read up to 1.25 GB/s to the disk buffer. However the motherboard to disk connection is typically either 400 MB/s or 750 MB/s per drive (and some drives really only support part of that). So somewhere between 2 and 6 drives in RAID0 is enough to saturate the buffering bandwidth. The buffer capacity is generally something like 32 or 64 MB per drive. For sustained writes exceeding that volume, you are limited by the buffer to disk bandwidth, which is typically about 100-150 MB/s on a 10k RPM drive. So if your writes/reads are very large, you could take ~10 drives to max out the theoretical capacity. For random reads, most of the data will come from disk (i.e. no buffering) so again somewhere in the neighborhood of 10 drives is a theoretical limit on what is useful. Also keep in mind that the "fake raid" controllers on many consumer motherboards offload some of the raid computations to the system CPU. For RAID 0 this can mean a few percent of a CPU core per drive (RAID 5 is much worse). At a practical level, you probably wouldn't see much if any benefit from 10 disks beyond what you get from 3 or 4 unless disk access is a really large part of what the computer does. Keep in mind that most games are limited by some combination of CPU, graphics card(s), and RAM. Once you've loaded all of the graphics (or whatever) for a level into RAM, there isn't much work that the hard drive needs to do while playing. As mentioned above, when a disk needs to read lots of random files, latency is more important than bandwidth. RAID 0 does very little for latency, so several 10k drives will be about the same latency as one. On the other hand you can get excellent latency improvements by using a single SSD instead. So a lot still depends on the workflow. Personally, rather than buying six or ten 10k drives, I would probably look at PCI-e SSDs, like this [1], which essentially offer performance like a RAID 0 of SSDs (very high read / write speeds and low latency) albeit at high cost and with much lower capacity than traditional hard drives. Dragons flight (talk) 18:33, 12 October 2011 (UTC)

Thank you Dragons flight! I have a few follow up questions; How can i tell if a motherboard offloads some of the raid computations on to the CPU? Is there a consumer grade mobo with a "true" raid controller? Or what should i look for in a PCI raid controller? As for the SSD, i do love the idea of SSD and would love to play around with one... or a raid full of em, but for the moment i found a really good deal on 10k RPM drives (less than $10 each for 80Gb and guaranteed to be working) Thank you – Elliott(Talk|Cont)  21:00, 13 October 2011 (UTC)

Is there an API to LockUpCPU?

Once, sometimes twice a day, my Anti-Spyware software decides it needs to run RIGHT NOW, regardless of what else I'm doing, and it proceeds to "lock up" (or "freeze") my system (WinXP) for 14-18 minutes.

This is apparently a well-known phenomenon, but I'm curious to know how they do it: while their whatever-it-is is running,

• The start menu pops, but you can't click on anything;
• Ctrl-Alt-Del won't display

• (meaning, you can't start task manager);

• You can't raise a window from the taskbar;
• The system clock can't even get enough cpu cycles to advance --

and this lasts for 15 minutes or so. Yes, I said MINUTES. On a 2.992 GHz processor.

Is it likely that they're really so bloody efficient that they never need to relinquish the cpu, or wait for I/O, or have a timeslice expire? Or is there a Windows API that actually allows them to say "GO AWAY, THE CPU IS MINE AND I'M NOT SHARING WITH ANYBODY!!" ?

Got a clue for me? Thanks! --DaHorsesMouth (talk) 21:38, 11 October 2011 (UTC)

The antivirus is not explicitly hogging the CPU with a "Lock Up Computer" API (that would be called a deadlock, and is never an intentional part of any program or hardware design - there is no "deadlock()" API in Windows). However, antivirus programs typically run with administrator privileges, and the programmers may have designed the software to run with high priority. Consequently, the antivirus program is prioritized over other tasks - including the processes that manage your user-interface and mouse-click handling. If you are asking "how," this is by setting the process priority. Here is one possible method, from Microsoft Developer Network: C/C++ Code Example: Setting Task Priority. If you are asking "why" the antivirus does this, it's probably fair to say "because it is poorly designed." The developers may justify this design-choice in a variety of ways, but it is my opinion that antivirus programs disrupt a system more than they protect it. Nimur (talk) 22:30, 11 October 2011 (UTC)

Excellent and perfectly clear -- Thanks, Nimur!

I am aware of nice(-1) in unix, which can only change its own priority within its own process group; this seems to go WAY beyond that restriction!

--DaHorsesMouth (talk) 22:50, 11 October 2011 (UTC)

This won't help if you can't get to Task Manager, but if you can, and if you have a multicore CPU, you can right-click on any process in Task Manager and choose "Set Affinity" to restrict the process to hogging only a single core of the CPU. I use this often to reduce Microsoft Outlook's hogging predisposition. Comet Tuttle (talk) 16:26, 12 October 2011 (UTC)

Can I go off at a tangent old bean? Are you absolutely 100% sure your anti-spyware is a proper & legitimate piece of software? There's an awful lot of spyware/malware/badware etc disguised as legitimate anti-virus/anti-malware/anti-spyware software. If your software isn't actually what you think it is that could explain the problem old chap. Quintessential British Gentleman (talk) 23:11, 12 October 2011 (UTC)

Quantum annealing

Why do so many people object to D-Wave one being a viable quantum computer if the entry on quantum annealing here on Wikipedia seems to imply that it has been proven, practically speaking. Is it because it hasn't been proven to be mastered (quantum annealing that is)? Layman's terms, please. Lighthead ^þ 22:40, 11 October 2011 (UTC)

I also want to ask if decoherence has anything to do with quantum annealing. That in and of itself might answer my question. Lighthead ^þ 22:45, 11 October 2011 (UTC)

Just because a company has announced something doesn't mean that their product is going to pan out. They could be scamming investors, in the extreme case. Scott Aaronson, a complexity researcher at MIT, has been discussing his reasons for skepticism about their claims. Paul (Stansifer) 12:18, 12 October 2011 (UTC)

Yeah, I guess that makes sense. Thanks for the info. Lighthead ^þ 19:10, 12 October 2011 (UTC)