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  • Cannot access system after deleting passwd file

    - by joao rodrigo leao
    I was trying to change my user name and also my /home/username and my system started to crash. I deleted the passwd file but I had a backup named passwd_bkp. I tried to rename this passwd_bkp as passwd and it did not work. No commands were being executed... I was in a terminal window. I re-started my system and now I cannot login. The GRub loads two options: Linux and recovery mode. I tried to open a sessions as root but it says the file system is corrupted. I cannot access my files. Did I lose all my files?

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  • Elmah

    - by csharp-source.net
    LMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for re-compilation or re-deployment. Once ELMAH has been dropped into a running web application and configured appropriately, you get the following facilities without changing a single line of your code: * Logging of nearly all unhandled exceptions. * A web page to remotely view the entire log of recoded exceptions. * A web page to remotely view the full details of any one logged exception. * In many cases, you can review the original yellow screen of death that ASP.NET generated for a given exception, even with customErrors mode turned off. * An e-mail notification of each error at the time it occurs. * An RSS feed of the last 15 errors from the log.

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  • car crash android game

    - by Axarydax
    I'd like to make a simple 2d car crashing game, where the player would drive his car into moving traffic and try to cause as much damage as possible in each level (some Burnout games had a mode like this). The physics part of the game is the most important, I can worry about graphics later. Would engine like emini or box2d work for this kind of game? Would Android devices have enough power to handle this? For example if there were about 20 cars colliding, along with some buildings, it would be nice if I could get 20 fps.

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  • Sage lance Sage CRM Express, une solution de gestion des clients spécialement conçue pour les PME

    Sage lance Sage CRM Express Une solution de gestion des clients pour les PME Sage a réalisé une étude auprès de ses clients qui montre que 80% des PME disposent de moins de 4 commerciaux et sont en attente d'un outil pour leur suivi clients qui peut s'interfacer facilement à leur solution de gestion commerciale existante. Pour répondre à cette attente, Sage a donc annoncé la sortie de Sage CRM Express. Intégrée de manière native à Sage 100 ou proposée en mode stand-alone, cette nouvelle offre s'adresse donc aux PME de moins de 4 commerciaux. Sage CRM Express est un outil assez simplequi tente de répondre à l'ensemble du processus client (avant-vente, vente, recouvrement, ...

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  • Our Geek Trivia App for Windows 8 is Now Available Everywhere

    - by The Geek
    When we first released our Geek Trivia app, it was sadly only available in the US store for Windows 8, but now you can get it no matter where you live. It’s completely free, so get your copy right now! For those that aren’t familiar with this app—it’s really quite simple: if you want your daily dose of Geek Trivia to show up on a Live Tile on your Windows 8 Start Screen, get this app. We’ve also got quizzes, loads of previous trivia, and we’ll be adding even more features in the near future. Our Geek Trivia App for Windows 8 is Now Available Everywhere How To Boot Your Android Phone or Tablet Into Safe Mode HTG Explains: Does Your Android Phone Need an Antivirus?

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  • Upgrading Agent Controllers in Oracle Enterprise Manager Ops Center 12c

    - by S Stelting
    Oracle Enterprise Manager Ops Center 12c recently released an upgrade for Solaris Agent Controllers. In this week's blog post, we'll show you how to upgrade agent controllers. Detailed instructions about upgrading Agent Controllers are available in the product documentation here. This blog post uses an Enterprise Controller which is configured for connected mode operation. If you'd like to apply the agent update in a disconnected installation, additional instructions are available here. Step 1: Download Agent Controller Updates With a connected mode Ops Center installation, you can check for product updates at any time by selecting the Enterprise Controller from the left-hand Administration navigation tab. Select the right-hand Action link “Ops Center Downloads” to open a pop-up dialog displaying any new product updates. In this example, the Enterprise Controller has already been upgraded to the latest version (Update 1, also shown as build version 2076) so only the Agent Controller updates will appear. There are three updates available: one for Solaris 10 X86, one for Solaris 8-10 SPARC, and one for all versions of Solaris 11. Note that the last update in the screen shot is the Solaris 11 update; for details on any of the downloads, place your mouse over the information icon under the details column for a pop-up text region. Select the software to download and click the Next button to display the Ops Center license agreement. Review and click the check box to accept the license agreement, then click the Next button to begin downloading the software. The status screen shows the current download status. If desired, you can perform the downloads as a background job. Simply click the check box, then click the next button to proceed to the summary screen. The summary screen shows the updates to be downloaded as well as the current status. Clicking the Finish button will close the dialog and return to the Browser UI. The download job will continue to run in Ops Center and progress can still be viewed from the jobs menu at the bottom of the browser window. Step 2: Check the Version of Existing Agent Controllers After the download job completes, you can check the availability of agent updates as well as the current versions of your Agent Controllers from the left-hand Assets navigation tab. Select “Operating Systems” from the pull-down tab lets to display only OS assets. Next, select “Solaris” in the left-hand tab to display the Solaris assets. Finally, select the Summary tab in the center display panel to show which versions of agent controllers are installed in your data center. Notice that a few of the OS assets are not displayed in the Agent Controllers tab. Ops Center will not display OS instances which do not have an Agent Controller installation. This includes Enterprise Controllers and Proxy Controllers (unless the agent has been activated on the OS instance) and and OS instances using agentless management. For Agent Controllers which support an update, the version of agent software (in this example, 2083) appears to the right of the currently installed version. Step 3: Upgrade Your Agent Controllers If desired, you can upgrade agent controllers from the previous screen by selecting the desired systems and clicking the upgrade button. Alternatively, you can click the link “Upgrade All Agent Controllers” in the right-hand Actions menu: In either case, a pop-up dialog lets you start the upgrade process. The first screen in the dialog lets you choose the upgrade method: Ops Center provides three ways to upgrade agent controllers: Automatic Upgrade: If Agent Controllers are running on all assets, Ops Center can automatically upgrade the software to the latest version without requiring any login credentials to the system SSH using a single set of credentials: If all assets use the same login credentials, you can apply a single set to all assets for the upgrade process. The log-in credentials are the same ones used for asset discovery and management, which are stored in the Plan Management navigation tab under Credentials. SSH using individual credentials: If assets use different login credentials, you can select a different set for each asset. After selecting the upgrade method, click the Next button to proceed to the summary screen. Click the Finish button to close the pop-up dialog and start the upgrade job for the agent controllers. The upgrade job runs a series of tasks in parallel, and will upgrade all agents which have been selected. Once the job completes, the OS instances in your data center will be upgraded and running the latest version of Agent Controller software.

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  • grub/burg listing a lot of os's

    - by Matthew
    I guess I've got more than one ubuntu installation (either two or three) along with a windows 7 installation. Each of the ubuntu installations also list something extra (maybe like a safe mode?) within grub. Firstly, how do I remove the ubuntu installations I don't use? (how do I first identify the one I do use? I log into it after booting it, but how do I delete the others) Also, how do I leave just a Windows 7 option and an Ubuntu option?

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  • Ubuntu 12.10 stopped during booting

    - by Alberto
    Good morning, I'm very new to Ubuntu. I decided to change to Ububtu (12.10) for my old laptop (Compaq Presario R3000 with AMD Athlon XP 2800+) that previously used Windows XP. After the installation, the PC restarted but, after a certain activity of the HDD stopped. Menwhile, no information from the screen (blank). Then I retried in recovery mode and the activity stopped at a certain point. I write the last two lines: [ 11.020922] pcmcia_socket pcmcia_socket0: cs: IO port probe 0x3000-0x7fff: [ 11.021676] excluding 0x3000-0x30ff 0x3400-0x34ff 0x3800-0x38ff 0x3c00-0x3cff I don't know how to solve the problem. Thanks in advance for the help.

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  • SQL Azure Data Sync

    - by kaleidoscope
    The Microsoft Sync Framework Power Pack for SQL Azure contains a series of components that improve the experience of synchronizing with SQL Azure. This includes runtime components that optimize performance and simplify the process of synchronizing with the cloud. SQL Azure Data Sync allows developers and DBA's to: · Link existing on-premises data stores to SQL Azure. · Create new applications in Windows Azure without abandoning existing on-premises applications. · Extend on-premises data to remote offices, retail stores and mobile workers via the cloud. · Take Windows Azure and SQL Azure based web application offline to provide an “Outlook like” cached-mode experience. The Microsoft Sync Framework Power Pack for SQL Azure is comprised of the following: · SqlAzureSyncProvider · Sql Azure Offline Visual Studio Plug-In · SQL Azure Data Sync Tool for SQL Server · New SQL Azure Events Automated Provisioning Geeta

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  • Claims-based Identity in .NET 4.5 and Windows 8

    - by Your DisplayName here!
    There was not a ton of new information about WIF and related technologies at Build, but Samuel Devasahayam did a great talk about claims-based access control that contained some very interesting bits of information with regards to future directions. From his slides: Windows 8 Bring existing identity claims model into the Windows platform Domain controller issues groups & claims Claims (user and device) sourced from identity attributes in AD Claims delivered in Kerberos PAC NT Token has a new claims section Enhanced SDDL API’s to work with claims Enhanced user mode CheckAccess API’s to work with claims New ACL-UX Target audits with claims-based expressions WIF & .NET 4.5 WIF is in the box with .NET Framework 4.5 Every principal in .NET 4.5 is a ClaimsPrincipal ADFS 2.1 ADFS 2.1 is available now as a in-box server role in Windows 8 Adds support for issuing device claims from Kerberos ticket

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  • Installation taking a very long time

    - by user290522
    I am installing Ubuntu 14.04(32-bit) on my laptop (Compaq Presario V2000), and after about 7 hours, it is still in Congiguring bcmwl-kernel-source (i386) mode. The messages I read are as follows: ubuntu kernel: [22814.858163] ACPI: \_SB_.PCI0.LPC0.LPC0.ACAD: ACPI_NOTIFY_BUS_CHECK event: unsupported with the numbers in the square brackets increasing. I have had Windows XP professional on this laptop, and I am erasing it. I am not sure if I should turn off the laptop, and start all over again. About 4 years ago I installed Ubuntu on this laptop, and that was very fast. The only problem I encountered was my wireless, and could not make it to work, and switched back to Windows. I appreciate any comments regarding this installation taking such a long time.

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  • The perils of double-dash comments [T-SQL]

    - by jamiet
    I was checking my Twitter feed on my way in to work this morning and was alerted to an interesting blog post by Valentino Vranken that highlights a problem regarding the OLE DB Source in SSIS. In short, using double-dash comments in SQL statements within the OLE DB Source can cause unexpected results. It really is quite an important read if you’re developing SSIS packages so head over to SSIS OLE DB Source, Parameters And Comments: A Dangerous Mix! and be educated. Note that the problem is solved in SSIS2012 and Valentino explains exactly why. If reading Valentino’s post has switched your brain into “learn mode” perhaps also check out my post SSIS: SELECT *... or select from a dropdown in an OLE DB Source component? which highlights another issue to be aware of when using the OLE DB Source. As I was reading Valentino’s post I was reminded of a slidedeck by Chris Adkin entitled T-SQL Coding Guidelines where he recommends never using double-dash comments: That’s good advice! @Jamiet

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  • What is the correct way to handle debug output in Java?

    - by Federico Zancan
    As my current Java projects grow bigger and bigger, I feel a likewise growing need to insert debug output in several points of my code. To enable or disable this feature appropriately, depending on the opening or closure of the test sessions, I usually put a private static final boolean DEBUG = false at the beginning of the classes my tests are inspecting, and trivially use it this way (for example): public MyClass { private static final boolean DEBUG = false; ... some code ... public void myMethod(String s) { if (DEBUG) { System.out.println(s); } } } and the like. But that doesn't bliss me out, because of course it works but there could be too many classes in which to set DEBUG to true, if you are not staring at just a couple of them. Conversely, I (like - I think - many others) wouldn't love to put the whole application in debug mode, as the amount of text being output could be overwhelming. So, is there a correct way to architecturally handle such situation or the most correct way is to use the DEBUG class member?

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  • Purple screen on boot, iMac

    - by Eugene B
    I have just installed Ubuntu 13.10 (special iMac iso found here) on the new iMac (dual boot). Installation of rEFIt was completed successfully, as well as the installation of Ubuntu itself. After the final reboot, rEFIt sees this distributive and allows the choice. When I select "Boot linux from HD", it sends me to grub screen, where I can select Ubuntu. And then it gets stuck on the purple screen (smpboot: Booting Node 0, Processors #1 -- for the recovery mode) with no further action. Does anybody know a solution to this problem? P.S.: I have also tried both 32 and 64-bit pc distributives (occasionally) with the same result.

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  • Why did the upgrade from 11.10 to 12.04 ruin my system?

    - by Jared
    After upgrading from Ubuntu 11.10 to 12.04, when I log in, everything is ruined. It's all black, blank white icons, blank black icons on the start menu, and well, nothing works. If I open up Chromium, it looks as though it's in high contrast mode. Is this a bug? Any ideas what could have happened? Can I get 11.10 back? Some photos (can't connect to network in Ubuntu so I had to take pictures with phone): http://i.stack.imgur.com/2dwKl.jpg http://i.stack.imgur.com/N4nA3.jpg http://i.stack.imgur.com/LNFje.jpg

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  • Ubunti 12.10 wake on lan not working with Realtek 8139

    - by f.cipriani
    My pc doesn't wake up when receiving a magic packet from a pc connected to the same router. ethtool: fcipriani@ubuntu:~$ sudo ethtool eth0 Settings for eth0: Supported ports: [ TP MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Supported pause frame use: No Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Advertised pause frame use: No Advertised auto-negotiation: Yes Link partner advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Link partner advertised pause frame use: No Link partner advertised auto-negotiation: Yes Speed: 100Mb/s Duplex: Full Port: MII PHYAD: 32 Transceiver: internal Auto-negotiation: on Supports Wake-on: pumbg Wake-on: g Current message level: 0x00000007 (7) drv probe link Link detected: yes I have enabled all the wake up features in my bios, and I have verified the magic packet gets to the pc. I suspect the main problem is that the NIC light is completely turned off after the shutdown, but even after spending a lot of time researching I can't understand if this is a limit of my network card, my mobo, or something in the OS which needs to be configured correctly in order to leave the NIC in stand by mode with the light flashing. the NIC is Realtek 8139, the motherboard Asus P5L13L-X

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  • Install Ubuntu on Mac OS X Mavericks, MacBook Air

    - by Unknown
    I was wondering if its okay to install Ubuntu on my Macbook Air, and if it is okay please let me know the procedure. I would prefer to do it by NOT using reFind (not sure what the name is). The following is my system specification. Hardware Overview: Model Name: MacBook Air Model Identifier: MacBookAir6,2 Processor Name: Intel Core i5 Processor Speed: 1.3 GHz Number of Processors: 1 Total Number of Cores: 2 L2 Cache (per Core): 256 KB L3 Cache: 3 MB Memory: 8 GB System Software Overview: System Version: OS X 10.9.2 (13C1021) Kernel Version: Darwin 13.1.0 Boot Volume: Macintosh HD Boot Mode: Normal MacBook Air (13-inch Mid 2013), OS X Mavericks (10.9.2)

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  • Global menu stopped working for most applications

    - by ltorgo
    I have Ubuntu 12.04 32 bits and I had been enjoying global menus and HUD since the beginning. However, for some strange reason, I stopped having global menus for most applications and thus no HUD fun anymore. Actually, the only two applications where I continue to have global menus are Thunderbird and Firefox, so not sure if it has something to do with these two... I've already browsed through some similar reports and already tried the following: checking if indicator-appmenu was installed. tried to use Unsettings to switch on and off, with reboots in the middle, global menus. logged in with a different user to see if it was some configuration of my user. also checked, using dconf-editor that, com ? canonical ? indicator ? appmenu ? menu-mode = "global" Any hint/help would be appreciated! Thank you in advance

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  • How can I disable usb-autosuspend for a specific device?

    - by black_puppydog
    This is related to the issue discussed in this question. Summary: the mouse freezes when operating on battery since it is autosuspended after a certain time and needs more time to wake up. Disabling usb-autosuspend for the mouse's receiver in powertop is a temporary solution but does not survive a reboot. How can I permanently disable the usb autosuspend for only one specific device? A solution that does not involve installing additional packages is preferred (after all, I want to disable something) but not required. Removing powertop (which seems to be a solution for some) is not what I want - I like poertop... And installing laptop-mode-tools to disable usb_autosuspend alltogether is not what I want, either, thus the new question. Also: will this affect the battery of my notebook? The logitech unifying receiver for the mouse stays connected all the time, so if that prevents the autosuspend from happening for all devices that would probably be bad.

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  • Automatically analyze excel files

    - by dole doug
    I have to replicate a manual generation of a large number of excel files. I started to manually track the relations between cells ( files, formulas, etc). I also had a talk with the person which generates those files. For now I have a general understanding about how the excel files are generated, but "devil is in the details". I assume that I can write a script which will generate the hierarchy between cells and files, but this might require the same effort as manually noticing the relations. Also, I'm afraid that I'm not too experienced and my app is more prone to error approach than a manual analyze. How to handle this problem? Do you know about an open source project which analyze the excel files in a recursive mode following the formulas ?

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  • SSD Tweaks for Ubuntu 12.04

    - by Mustafa Erdinç
    I need to tweak my Dell XPS 13z SSD for maximum performance and life cycle than I read the solutions explained here, but it is for 11.10 and my fstab is different. For now my fstab is looks like this: proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda1 during installation UUID=abf5ce9e-bdb7-4b2f-a7bd-bbd9efa72a98 / ext4 errors=remount-ro 0 1 # /home was on /dev/sda2 during installation UUID=491427b2-7482-4483-b6eb-7c564b991aff /home ext4 defaults 0 2 # swap was on /dev/sda3 during installation #UUID=7551000d-e708-4e0f-9fd2-9f93119f63fb none swap sw 0 0 /dev/mapper/cryptswap1 none swap sw 0 0 tmpfs /tmp tmpfs mode=1777 And my rc.local is looks like this: echo noop > /sys/block/sda/queue/scheduler echo deadline > /sys/block/sda/queue/scheduler echo 1 > /sys/block/sda/queue/iosched/fifo_batch exit 0 Do you have any suggestions, what should I do? Regards

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  • Why isn't Grub2 using custom resolution?

    - by beanaroo
    I hope somebody can help me with this... Running Ubuntu 12.10 I am trying to get Grub2 to use a resolution of 1600x900... I have checked vbeinfo and hwinfo --framebuffer which both provide: Mode 0x037f: 1600x900 (+6400), 24 bits This resolution has worked on previous Ubuntu and Fedora installs. Here is my /etc/default/grub: http://paste.ubuntu.com/1308444/ Line 25 = GRUB_GFXMODE="1600x900" As well as my /boot/grub/grub.cfg: http://paste.ubuntu.com/1308446/ Line 72 = set gfxmode=1600x900 I have tried using grub-customizer: Why is it not taking effect?? I have tried different resolutions... Backgrounds and font colours are changeable. Thank you for your insight.

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  • Right click menu stopped working in firefox

    - by umpirsky
    Right click menu stopped working in firefox as well as address bar auto completion. I have tried removing and installing firefox again from software center, but the problem persist. UPDATE: Hehum, strange. I wanted to restart in safe mode, clicked help menu, and noticed that menu is ubuntu software center menu! Then cllosed software center, and menu was gone. So now right click is working, auto complete is working, but there is no main menu! Probably unity global menu integration problem. Also, there is no firefox in launcher nor alt+tab any more. Any idea? UPDATE: For some reason, it works after computer restart :o

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  • Customizing UPK outputs (Part 2 - Player)

    - by [email protected]
    There are a few things that can be done to give the Player output a personalized look to match your corporate branding. In my previous post, I talked about changing the logo. In addition to the logo, you can change the graphic in the heading, button colors, border colors and many other items. Prior to making any customizations, I strongly recommend making a copy of the existing Player style. This will give you a backup in case things go wrong. I'd also recommend that you create your own brand. This way, when you install the newest updates from us, your brand will remain intact. Creating your own brand is pretty easy. Make sure you have modify permissions on the publishing styles directory, if you are using a multi-user installation. Under the Publishing/Styles folder, create a new folder with your company name. Copy all the publishing styles from the UPK folder to your newly created folder. Now, when you go through the Publishing wizard, you will have two categories to choose from: the UPK category or your custom category. Now, for updating the Player output. First, the graphic that appears on the right hand side of the Player. If you're using a multi-user installation, check out the player style from your custom brand. Open the player style. Open the img folder. The file named "banner_image.png" represents the graphic that appears on the right hand side of the player. It is currently sized at 425 x 54. Try to keep your graphic about the same size. Rename your graphic file to be "banner_image.png", and drag it into the img folder. Save the package. Check in the package if you are in a multi-user installation. You've just updated the banner heading! Next, let's work on updating some of the other colors in the player. All the customizable areas are located in the skin.css file which is in the root of the Player style. Many of our customers update the colors to match their own theme. You don't have to be a programmer to make these changes, honest. :) To change the colors in the player: Make a copy of the original skin.css file. (This is to make sure you have a working version to revert to, in case something goes wrong.) Open the skin.css file from the Player package. You can edit it using Notepad. Make the desired changes. Save the file. Save the package. Publish to view your new changes. When you open the skin.css, you will see groupings like this: .headerDivbar { height: 21px; background-color: #CDE2FD; } Change the value of the background-color to the color of your choice. Note that you cannot use "red" as a color, but rather you should enter the hexadecimal color code. If you don't know the color code, search the web for "hexadecimal colors" and you'll find many sites to provide the information. Here are a few of the variables that you can update. Heading: .headerDivbar -this changes the color of the banner that appears under the graphic Button colors: .navCellOn - changes the color of the mode buttons when your mouse is hovering on them. .navCellOff - changes the color of the mode buttons when the mouse is not over them Lines: .thorizontal - this is the color of the horizontal lines surrounding the outline .tvertical - this is the color of the vertical lines on the left and right margin in the outline. .tsep - this is the color of the line that separates the outline from the content area Search frame: .tocSearchColor - this is the color of the search area .tocFrameText - this is the background color of the TOC tree. Hint: If you want to try out the changes prior to updating the style, you can update the skin.css in some content you've already published for the player (it's located in the css folder of the player package). This way, you can immediately see the changes without going through publishing. Once you're happy with the changes, update the skin.css in player style. Want to customize more? Refer to the "Customizing the Player" section of the Content Development manual for more details on all the options in the skin.css that can be changed, and pictures of what each variable controls. I'd love to see how you've customized the player for your corporate needs. Also, if there are other areas of the player you'd like to modify but have not been able to, let us know. Feel free to share your thoughts in the comments. --Maria Cozzolino, Manager of Requirements & UI Design for UPK

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 5

    - by MarkPearl
    Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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