Wikipedia:Reference desk/Archives/Computing/2009 June 9

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June 9[edit]

Undelete, and, searching the Reference Desk[edit]

I'm looking for the ideal free undelete software that runs under Windows Vista 64-bit. (I tried searching the refdesk; I would have assumed this is a FAQ; but unfortunately searching for "undelete" seems to come up with a billion entries which do not mention the word "undelete", because it seems to be a keyword embedded somehow in the archives.) Tempshill (talk) 04:40, 9 June 2009 (UTC)

this might work for you. — Ched :  ?  10:24, 9 June 2009 (UTC)
There are a couple things mentioned at List_of_portable_software#Partition.2FFile_Recovery, and a general overview at: Data recovery. Hope that helps. — Ched :  ?  10:28, 9 June 2009 (UTC)
Recuva works -- penubag  (talk) 03:29, 10 June 2009 (UTC)
Try Glary Undelete, one of a nice collection of freeware in Glary Utilities. Here's the link. Mxvxnyxvxn (talk) 23:11, 15 June 2009 (UTC)
I've posted the search problem at the village pump. Jay (talk) 09:59, 11 June 2009 (UTC)


how to close lsass.exe savely ? —Preceding unsigned comment added by Shoor77 (talkcontribs) 07:38, 9 June 2009 (UTC)

lsass.exe is part of the winlogon process, and authenticates the user logging into that PC. Why are you wanting to close it? — Ched :  ?  10:18, 9 June 2009 (UTC)
See Local Security Authority Subsystem Service. Doesn't look like a particularly good idea to end it honestly. Gunrun (talk) 10:19, 9 June 2009 (UTC)
(ec)lsass.exe is supposed to run the whole time you are using the computer. You can force close it through the Task Manager, but that will cause the machine to restart, see Local Security Authority Subsystem Service. If you have more than one running, one may be Isass (capital I instead of lower case l)which would be a virus. That can be removed with a good virus scanner.-KoolerStill (talk) 10:39, 9 June 2009 (UTC)

Asynchronous x86[edit]

Is there anything instrinsic to the x86 (or'x64') ISA that prevents an asynchronous version of the processor being made? (talk) 12:10, 9 June 2009 (UTC)

Could you explain what you mean by "asynchronous" here? What is your objective? Tempshill (talk) 14:38, 9 June 2009 (UTC)
See Asynchronous CPU. I think this is a theoretical question, but an implimentation could in theory give higher clock speeds and lower power consumption. -- Q Chris (talk) 14:48, 9 June 2009 (UTC)
Good, so one two persons now knows what asychronous means..
We all know what "asynchronous" means, you smartass. I was unfamiliar with Asynchronous CPU and thought you were asking some sort of question about motherboards with multiple CPUs. Tempshill (talk) 15:39, 10 June 2009 (UTC)
Just to clarify - I would guess the catch here would be if there is any programming mode or method (not non-standard) that requires a set of instructions to always take x clock cycles - my guess is no since cache tends to mess up overall timings - maybe an expert will know? (talk) 16:53, 9 June 2009 (UTC)
There will be changes noticeable to system programmers (in a very small number of cases). Code that relies on exact(ish) instruction timing is mostly limited to odd places like bitbanging i2c/spi on bios bringup and pre-os flash operations; for these people will have to rely on an external timer (or maybe the processor will boot initially into a predictable synchronous mode to make this stuff easy, and can be set to async once the bios has run). Cache isn't an issue in these cases, because cache isn't enabled yet (and neither is DRAM), and once the RAM is up the system programmer can control what's in cache (during this early boot phase when there's no great competition for resources). After that there will probably be some weird corner cases where other system level code makes assumptions about how long one piece of code takes to run vs another (perhaps spinlocks or memory barriers), but most device code already has to contend with its devices being desynchronised devices at the end of a lethargic system bus, so as long as on average things can keep up (which is an issue anyway) then they shouldn't care. At least for desktop and server programmers, even in the system, gone are the days when you'd need to stick in some NOPs until the raster is on the next line or the drum head has moved to the start of the track. -- Finlay McWalter | Talk 17:30, 9 June 2009 (UTC)
Thanks - I hadn't thought of spinlocks - though in general asychronous processors have their problems when trying to access shared resources - I think this would be an example of that case, though I'll have to think about it. <text color="00000> or even wonder what sort of madman ever creates a spinlock in the first place - theres a good chance no one will ever read this</text> —Preceding unsigned comment added by (talk) 18:38, 9 June 2009 (UTC)
There was a lot of work on asynchronous processors till about five years ago. Now the only place I hear about them is for things like smart cards or chips in passports. They should be good for a number of things like array processors or power saving or modular computational building blocks but it looks like familiarity has won out and their advantages are just not great enough. And with that I suppose some foundry will just go and prove me wrong by announcing some heavy duty processing application :) Dmcq (talk) 23:01, 9 June 2009 (UTC)
By the way the most interesting case I've come across where the number of cycles taken mattered was in an algorithm where they were able to decode the password one letter at a time because the check bombed out one letter at a time. Dmcq (talk) 23:07, 9 June 2009 (UTC)
What does the second paragraph mean? —Preceding unsigned comment added by (talk) 04:49, 10 June 2009 (UTC)
I guess you mean about the passwords since I phrased it unclearly. If a password check does a string comparison between the password and what it should be, or even their encrypted forms which is more normal, then the string comparison routine will stop as soon as it detects a difference. Timing the password check will tell how far the string comparison routine went. That way one only need use 256 probes at most per character of the check and so only a few thousand to decrypt the full password. Smaller differences like cache timings can also be used to gain information about passwords but they are much more difficult to exploit. An asynchronous processor for instance might have slightly different timings dependent on how many zeroes are in an operand. Having exactly the same instructions executed in all failure cases of a password check is very desirable.
More relevant to this question though is people do sometimes check a device again a couple of times after a command if it normally responds very quickly in that context. It can be faster overall than returning to user level and then getting interrupted again. There the device self times by its delay in answering. Dmcq (talk) 07:28, 10 June 2009 (UTC)
Thanks for clarifying - I couldn't make head or tail or the first description. (talk) 11:57, 10 June 2009 (UTC)

Google Street View UK[edit]

Is there a list where the next places in the UK that will be on streetview will be, i cant seem to find one... thanks, --Abc26324 (talk) 12:52, 9 June 2009 (UTC)

They don't publish one; they don't even announce when they do add stuff (people just notice). I've seen the car twice, in two different places that aren't yet covered on the live site, so clearly they're chewing through a lot of data for more places right now. Hopper Mine (talk) 14:01, 9 June 2009 (UTC)
They often announce new Street View cities on the Google LatLong BlogMatt Eason (Talk &#149; Contribs) 14:25, 9 June 2009 (UTC)
I have a friend who drives one of the Google Street View cars. According to him they've covered pretty much every built-up area in mainland UK. They are mostly doing update work now on places they've already covered. I think Google have a vast amount of data to go through, it's just a matter of time. -Phydaux (talk) 16:40, 9 June 2009 (UTC)

UK vat on computer DVD etc[edit]

When buying from online retailers in the UK many ship from Jersey. I have read that there may be a tax avoidance reason for this. Previously I assumed that the goods were often cheaper due to the companies not requiring store frontage etc.

Question what is VAT on computer DVDs etc? How do I know if I have avoided paying tax? Can anyone explain the 'goods under £18' sometimes mentioned?

As this may drift into the legal domain can someone also tell me what goverment department I should contact for specific clarification. If anyone can explain the basics of what is going on though, I would appreciate it - (it's unclear to me if I have broken the law) Thanks. (talk) 13:06, 9 June 2009 (UTC)

HM Revenue and Customs is the relevant body and to save you the tortuous task of trawling through their jungle of a website the page you want is this one - X201 (talk) 14:47, 9 June 2009 (UTC)
ok thanks - with your help I managed to find the information I needed. Now all I need is some replies to emails hopefully telling me they have already added the vat to my purchases...

using reconstructor withubuntu[edit]

I have been playing around with reconstructor and I cant figure out how to modify a ubutnu cd in to a live only cd. can some one please point me to a list of packages that can be removed from ubuntu but still keeping the ones nessary for hardware usage and for the x server . . thank you and sorry for the lack of links and for my bad spelling. I am on my phone right now. —Preceding unsigned comment added by Smileyhill (talkcontribs) 18:42, 9 June 2009 (UTC)


What's the biggest amount of music I can place into Winamp's library? Kurtelacić (talk) 19:04, 9 June 2009 (UTC)

Do you mean, maximum number of songs? Apparently any given playlist can have a maximum of 4,000 songs, but you can have probably an unlimited number of playlists. -- (talk) 20:39, 9 June 2009 (UTC)
I am looking for a specific number of gigabytes, if there is any. Kurtelacić (talk) 20:48, 9 June 2009 (UTC)
Winamp doesn't "contain" the music. The library contains a list of the music files, their location, and perhaps some other info too, but not the music itself. I presume the library has an ultimate maximum size, but I don't know what that is. The number of gigabytes of music is most likely governed by how much disk space you have. Astronaut (talk) 21:37, 9 June 2009 (UTC)
I can list over 5400 songs (about 25GB) with the "Playlist Editor" in Winamp. The playlist performance decreases with this amount of data, it can take a while to scroll and refresh. This is probably affected by hardware performance too. ~~ Ropata (talk) 07:54, 12 June 2009 (UTC)

Redirecting yahoo mail[edit]

I got yahoo mail recently as I wanted a Flickr account and a yahoo ID always includes email. I am happy with my current email service and would therefore like to know if it is possible to redirect yahoo to my msn account! Thanks. -- (talk) 20:16, 9 June 2009 (UTC)

You can get Yahoo! Mail Plus (which costs almost twenty dollars a year). More information here. Kushal (talk) 20:28, 9 June 2009 (UTC)
I don't see why you'd want to do this - presumably you're not giving out your Yahoo email address to anyone because you're happy with your current service, so you're not going to be receiving any emails at your Yahoo address. If you're worried about emails from Flickr going to your Yahoo address, you can always change your Flickr contact email hereMatt Eason (Talk &#149; Contribs) 20:30, 9 June 2009 (UTC)

You can set a re-direct on your yahoo mail so that it goes to a Yahoo account ( gives you details of how to achieve this. That way anything that goes to it will get redirected to the address you specify (presumably your MSN account). ny156uk (talk) 21:02, 9 June 2009 (UTC)

As a regular on Yahoo's equivalent of RefDesk, let me give you a workaround. The above redirections work only with the $19.95 Premium Mail. But as long as you don't give the Yahoo email to anyone, you'll only get Flckr-related mail on it. Go to My Account, Edit the email section and put your msn email, then choose that to be the primary email. The Yahoo one will still serve as your ID, but communications will go to the msn. While you are there turn Marketing Preferences to nil. This will redirect in-house mail from any Yahoo property.
You have also acquired a Universal Profile Card. From the Yahoo home page, choose Profile from the drop down under your name (top edge of page). Click Settings (top right) and scroll down to Hide My Profile, select and save. This way nobody will be able to search for you by name, ID or email address. - KoolerStill (talk) 03:28, 10 June 2009 (UTC)

Scripting language for image manipulation[edit]

Octave is fast but color images and IO are not so fun. PDL works well for color and Perl is good, but (at least PDL::ImageND::convolveND) is slow, > 1min vs Octave < 2s (???), though octave did it only for grayscale. The real question is in the title, can you tell any? It needs to have support for fft/convolution/stuff. -- (talk) 22:43, 9 June 2009 (UTC)

You might look at Processing (programming language); this example shows image convolution (although written in Processing, rather than part of its library). It seems people have done some pretty impressive stuff in Processing. Hopper Mine (talk) 23:12, 9 June 2009 (UTC)
I personally would try to stick with a general purpose language that has a fast library available. You might find Category:Graphics libraries useful. --Sean 12:36, 10 June 2009 (UTC)

Power Converters[edit]

Why does a power converter from 110V to 240V have a warning saying not for electronics that use above 25 watts even if the converter is rated from 0-2500 Watts? Is it safe to use with an electronic device (specifically iPods and digital cameras) that use over 25 watts, but less than 2500? Or can those use just an adapter as the products in question are all rated for a voltage of 100-240 despite saying recommended to be used in the US only?-- (talk) 22:55, 9 June 2009 (UTC)

A very small unit might only deliver 25 watts for something like charging a phone, but I guess you've got a higher end power converter there and that is 25 Amps instead of Watts which is enough for a power tool or microwave oven. I'd reread the spec carefully and see if it really is Watts. Dmcq (talk) 08:31, 10 June 2009 (UTC) Yes a small unit makes no sense, you only get things that small for directly powering small devices. Dmcq (talk) 08:45, 10 June 2009 (UTC)
See this Amazon review. -- Coneslayer (talk) 12:30, 10 June 2009 (UTC)
Thanks very much. That's really quite dreadfully horrible. It probably won't even work with some things that aren't normally considered as electronic because they also do switching like a power tool for instance. And I hate to think what it would do to a microwave. Dmcq (talk) 14:30, 10 June 2009 (UTC)
In fact I wonder what voltage they clip it to, I'd guess so the root mean square came out the same or even an iron might overheat. Dmcq (talk) 14:41, 10 June 2009 (UTC)
I'd very much doubt that product is legal if the review is correct - at least it wouldn't be in the UK, I imagine there are laws in the US that prevent potentially dangerous electrical devices (it would make a 'short circuit' in a transformer if the voltage is clipped to dc half the cycle...) Maybe the reviewer got it wrong - I would have guess it to be a switched mode power supply which would be possible and sensible?? (talk) 16:55, 11 June 2009 (UTC)
For the original question, if the appliances say "100-240 V, 50-60HZ" (like almost all things with trafos such as cellphone chargers), you can just use a simple adapter and don't need a transformer. At least that's what I do... Jørgen (talk) 18:29, 10 June 2009 (UTC)
Thank you. That is indeed what they say, so I will travel with them and adapters only. No converter. The packaging should really be more clear for converters.-- (talk) 00:43, 11 June 2009 (UTC)