Imac boot-up issue

My imac boot up with chime then apple log then circle under the logo then freeze for sometime and go gray forever. I tried the Resetting the NVRAM, I tried to boot on a option but it won't take my CD or recovery disc (it's doing the same thing) I tried booting with Shift S and do all the commands but still no luck. Now i'm stuck and don't know what to do
Please help!!!

Speedster1972,
It's extremely difficult to assist when there is no user profile completed. That information is vital so those trying to assist you can tell what version of OS X is installed and which iMac you have. I could provide some instructions but without knowledge of those two basics i'd still be guessing. Please complete your profile, however for this thread it will not show. On your next post please indicate what they are.

Similar Messages

My iMac boots up and I login and then I get a white screen. How do I fix this?

My iMac boots up ok. I get to the login screen where I can select which user to login as, however once I've selected a user account (it doesn't appear to matter which one) I then get a white screen.
I don't know where to look to identify my exact operating system as I cannot get to the Apple icon to check About This Mac.
I have booted up in safe mode, recovery mode and done fsck -fy , it all suggests my iMac is ok but I still get the white screen. Does anyone know what I should try next?

Does it boot okay in the Safe Mode and can you access the  menu there to see what OS you are running? While in the Recovery Mode, did you try running Disk Utility Repair Disk and Repair Permissions?
Startup - Gray, Blue or White screen at boot, w/spinner/progress bar
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Re: Wireless and Wired Network: probably using a dlink 825 dual n band wireless router.
1. How is a typical Dell/ vistax64 networked to an imac booted in vista x64?
2. How is a typical Dell/ vistax64 networked to an imac running vista x64 in emulation?
*3. how are they configured to simultaneously synch business files and digital images, that will originate from the dell, in situation 1 & 2 above?
I (might be) stuck getting a Dell/vista 64 to acquire digital dental x-rays in the treatment room, bec the sensor mfg'er says the drivers won't work(!) on a Mac booted in Vista, either way. But since the PC imaging app and PC practice management software works fine either way, the iMac will rule the Front Desk. I'm still not convinced about the driver PC only spec! ..... Please help me get the sync'ed networking configured. Thanks!

Hi there,
Could you provide the community with a little more information to help narrow troubleshooting? Specifically what is the model number for the printer? If you have difficulty locating the model number please use one of these guides to get it:
Deskjets
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=c01105883&...
Envy Series
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=c01105892&...
LaserJets
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=c01230412&...
Officejets
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=buu04090&l...
Photosmarts
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=c01105892&...
PSC
http://h10025.www1.hp.com/ewfrf/wc/document?tmp_renderType=findModel&cc=us&dlc=en&docname=buu04090&l...
You can say thanks by clicking the Kudos Star in my post. If my post resolves your problem, please mark it as Accepted Solution so others can benefit too.

My iMac boots up and the mouse curser will move but nothing responds to the click. I was in the Apple store today and they reset the permissions, but still same problem. Help!!!

My iMac boots up fine and the mouse appears to be working fine however nothing responds to the mouse click. I took it to the Apple store today and they checked and repaired the permissions. I brought it home and still have the same problem. Does anyone have any ideas?

Hi, thanks for trying to help!
I just blew out the dust and turned it on again to the same problem.
So I tried holding the shift key which did something but then on reboot I got the same problem but this time worse, see here...
So I tried the alt key but that just gave me two startup disk options, both of which didn't work (they led to the same problem).
Then I tried CMD+s and followed your instructions, see below...
I just held the power button down and turned it on again and the same problem happened again.
Any further thoughts?
Thanks!
Alex

X220 and z230 ThinkPad boot up issues

We have ran into the same recurring issue with the x220 and x230's. We are running windows 7 pro 64bit, and on a consistent basis we have boot up issues, were windows gets stuck after the bios. The computer needs to be rebooted several times for it to fully boot up. Our users do have docking stations as well, anyone else having this issue?

Hi
If you're hearing noises coming from the hard drive area chances are it is failing hard drive. In which case it may be possible to target disk mode to another mac and try and recover what you can using either drag/drop methods or something like DataRescue:
http://www.prosofteng.com/products/data_rescue.php
This ultimately could be a painfully slow experience. It really does depend on how 'screwed' the hard drive is? Only you can decide how important your data is and how much time you want to spend on it. There is a good possibility (if your data is absolutely vital) that a Data Recovery Specialist can recover the data for you? It can be very expensive. It all depends on what value you place on your data?
If your mac is still in Warranty you have an added dilemma. To qualify for a warranty replacement drive you have to send the drive back to Apple. Neither can you send it to the Data Recovery Specialist first and then send it to Apple. The reason being in all probability the Data Recovery Specialist will have to tamper with the drive in some way to stand a chance of recovering your valuable data. Tampering voids the warranty. Of course if you value your data higher than the cost of a new 3rd-party (cheap) or an Apple branded drive (ridiculously more expensive) then don't bother and replace the drive at your own expense.
Tony

Imac boots up into user account

At start up my imac boots into my wifes account evem though it has a password How can i get it to boot up into the users screen

You have to disable automatic login. Open System Preferences > Users & Groups > Login Options, and choose "Off" next to "Automatic login". After doing this, you will have to choose which user you want to log in with every time you start up your Mac.
You may have to press the padlock at the bottom left corner of the window first

Why won't my Intel iMac boot up, either from the internal hard drive or the DVD drive? It just displays a light grey screen, without any other icons, etc. The fact that it won't boot from the original system DVD is what baffles me the most. Any ideas?

Why won't my Intel iMac boot up, either from the internal hard drive or the DVD drive? It just displays a light grey screen, without any other icons, etc. The fact that it won't boot from the original system DVD is what baffles me the most. Any ideas? It uses the latest version of Mavericks. Thanks!

If the C key for Install Disc or R Command for OS X Recovery startup commands are not working, try holding the Option key for the Startup Manager.
see > Startup Manager: How to select a startup volume
If that does not work and you using a wireless keyboard, it may have become unpaired and you need to dig up a USB keyboard to invoke the startup commands.
For more on gray screen, see > Mac OS X: Gray screen appears during startup

My PC can connect to the airport extreme but with encryption it cannot connect to the internet my iMac has no issues, any help.

My PC can connect to the new airport extreme I just purchased but with encryption it cannot connect to the internet my iMac has no issues. If I open the airport exteme up and provide no security everything is fine which leads me to believe it is something with the encryption between the two devices. Not sure what step I'm missing here this shouldn't be this difficult.

Sorry, I should have been more clear. I am asking if the DNS IP addresses, not the IP addresses assigned by the DHCP service, are the same. DNS is like the Internet's version of the Yellow Pages. Your ISP typically will provide them to you or you can elect to use those provided by another source, like OpenDNS.
DNS is the service that translates a website's URL to its actual IP address so that you can access it. I am just trying to rule out that the PC is not configured properly with the correct DNS IP information.
The other thing to check is if the PC is configured to use a Proxy service. By default, it would not be.
Finally, what is the make & model of the PC. More importantly, if the PC is using either a PCI or USB wireless adapter, what is its make & model?

Imac booting into terminal window

Ever since updating to Mountain Lion my imac boots up showing the boot up script, sometimes it stops and I have to type exit or boot to get it going...I've spoken to Apple 'support' 6 times now and including a re-install they have talked me through a miriad of processes...none of them have worked.

Have you done this?
Install or Reinstall Lion/Mountain Lion from Scratch
Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Erase the hard drive:
1. Select Disk Utility from the main menu and click on the Continue button.
2. After DU loads select your startup volume (usually Macintosh HD) from the left side list. Click on
the Erase tab in the DU main window.
3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on the Security button and set the Zero
Data option to one-pass. Click on the Erase button and wait until the process has completed.
4. Quit DU and return to the main menu.
Reinstall Lion: Select Reinstall Lion/Mountain Lion and click on the Install button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

IMac Boot Sound Volume

Hi,
Why does my iMac boot chime change it's volume from time to time?. Some times it's really loud, and annoying. How do I tame it down a bit?
Thanks
Tristram

Tristram,
Like many in these posts will tell you, the boot sound is a good thing because it is a diagnostic signl that announces everything is ok with the system.
But I agree it does get pretty loud. If you want, you can press the mute button on the keyboard before shutting down or restarting to mute the start up sound as well.There is no other way to actually control the volume except to mute it.
To actually control the volume level of the chime, there are some hacks like StartupSound.prefPane available that do the job.
Hope this helps...

IMac boots to a black screen and shows blinking square cursor on top left

iMac boots to black screen and then shows flashing white square in the top left of the screen. After a few seconds an error message - i assume appears.
disc0s2 oxe0030005 undefined appears.
Does anyone know what this is?
Can view HDD using firewire
Can load diagnostic disc and run diagnostics with no errors

The disc0s2 should be your OS X boot volume. Have you tried starting from the Install DVD1? Start from the DVD and when you get to the OS X installer go to Disk Utility in the Utilities menu and select First Aid. Choose the top drive in the left hand column and repair. Repair as many times as necessary until no more repairs are reported. Quit Disk Utility. Then go to Startup Disk in the Utilities menu and choose the OS x volume on your Mac and restart.
Let us know what happens.

How do I prevent the Window Office applications from launching when my iMAC boots or recovers from sleep? I've tried System Preferences however the Office programs are not listed?

How do I prevent the Window Office applications from launching when my iMAC boots or recovers from sleep? I've tried System Preferences however the Office programs are not listed?

lunagirl wrote:
The first 3 apps listed are not installed because I have not run the activation assistant for the Office trial that came with the T61. Add/Remove programs has only these pre-installed apps:
Microsoft Office 2003 Web Components
Microsoft Office 2007 Primary Interop Assemblies
Microsoft Office Small Business Connectivity Components
MS SQL Server 2005
MS SQL Server Native Client
MS SQL Server Setup Support Files
MS SQL Server VSS Writer
Is the activation assistant one of them?
No, AFAIK should be listed as Microsoft Office Suite Activation Assistant
Rgds,
Ahti

MSI z87 g45 Boot up issues

So I built a computer for my sister and her husband and it has been having some boot up issues,Here are the computer parts:
wiindows 7 64bit
MSI Z87 G45 Gaming motherboard
INTEL CORE I-7 4770K 3.5GHZ
RADEON HD 5700 GPU
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1866
kINGSTON 64 GB SSD ( spare part, not sure the numbers)
Sunbeam PSU-H680-REV-US 680W ATX 12V 2.0 Power Supply - OEM
Seagate Barracuda ST2000DM001 2TB 7200 RPM
ASUS Black 12X BD-ROM 16X DVD-ROM 48X CD-ROM SATA Internal Blu-ray Drive Model BC-12B1ST/BLK/B/AS
I've cleared both the HDD and SSD and now I'm looking to check the msi z87 g45 mobo, The computer starts up and sits on a2 for a while and then sometimes it fails to detect the SSD and says a0 and then I have to go back into the bios after I reset the computer again and maybe it detected the SSD and I can set it to boot from that again because it constantly changes the boot order, and sometimes it gives a blue screen when nearly into windows and then restarts, I had transferred some data from their old computer to this one and the data had virus's in it and I didnt know so I eventually found out and a day later and got rid of them all and the computer started behaving better but not fixed, faster mainly, I don't know if the virus may have altered some files so, I have a few more things to try, any help would be appreciated.
(Something I forgot to mention is that when I unplugg the HDD all the issues go away, the computer seems to work fine, But there are no issues with the hdd, ive tested it with seatools and I plugged it into my computer and restarted mant times as well as used my computer for a while and nothing, the HDD is fine, the start up on their computer sits on a2 for a long time when it isnt going to work and it only happens with the 2tb seagate HDD plugged in)

which storage drive holds the boot files the SSD or the HDD? the ATA mode of the BIOS needs to remain in the same mode it was when Windows was deployed to the storage drive. next the only way a BIOS settings will change with out user input is if the Li cell battery is going dead/the BIOS is getting reset frequently. sounds like you're about at square one, I'd format the Seagate 2TB HDD, install windows onto that either in RAID or AHCI mode whichever your preference, you can use the 64GB SSD as caching later if you use RAID mode, if AHCI the 64GB could be spare. I don't understand the SSD as boot drive method, it doesn't make sense the solid state storage is volatile meaning it degrades over time, the HDD isn't and the performance gain isn't going to change the way you use your PC. AHCI has it's advantages it's up to you. Following those steps is the only way you're going to keep the computer booting on a regular basis. You shouldn't need to manually configure which storage drive to initialize/boot from first, the BIOS automatically goes through your devices to find boot files then boots from the first one with boot files, it won't even try to boot from a device without boot files, because it can't. Just to reiterate the BSOD you speak of sounds similar to the ATA mode changing to something other than what it was when Windows was deployed to the device.

Magic Trackpad / iMac wake up issue.

Hello,
Does anyone know of a fix for the following Magic Trackpad / iMac wake up issue please?
Basically hooked up a Magic Trackpad that was bought several months ago now and found that it works great however the 'click' functionality does not work whilst waking up my iMac. The cursor moves as it should however it's not possible to click onto either a registered account nor guest account in order to enter a password to wake-up from screensaver.
To get around this I've had to pair-up my Magic Mouse again which is not ideal.
A fix for this would be appreciated.
OS installed: OSX 10.7.5.
Thank you.

Just my .02, but why do you want a screen save? I was told a long time ago by some engineers not to have your screen saver running. Just non essential. Me, I have none of our computers doing so. They time out and sleep in between, so the hard drives and logic boards power down, if not shut down completely.
As for you situation, I had the same problem a while back and believed it was one or more of the apps. in the back ground. Could even be the UPS. Either re load your OS to check any corruption. And/or, check your login list of apps. and finder to see what is running without your knowledge or in the background, then closing out of open programs one by one prior to the screen saver engaging and see if it changes things.

IMac boot issues, panic report since Yosemite upgrade

I've been having serious issues getting my iMac to boot ever since upgrading to Yosemite - Basically it turns on, makes the chiming sound, goes to the white screen with the apple logo and progress bar and at about 1/3 of the way, goes blank white/black, then either reboots on a loop or freezes until I'm forced to manually shut it down.
When I boot in safe mode, I get this ProblemReport:
Anonymous UUID:       CFB3276F-B26B-291C-F495-653576C46E49
Wed Oct 22 16:58:32 2014
*** Panic Report ***
panic(cpu 0 caller 0xffffff800c77a590): "a freed zone element has been modified in zone ipc importance inherit: expected 0x58a9e1599e00910 but found 0xbfbfbf00bfbfbf, bits changed 0x53521aa995fb6af, at offset 0 of 88 in element 0xffffff801f2c7e40, cookies 0x3f001114074f583a 0x53521aa995fb6af"@/SourceCache/xnu/xnu-2782.1.97/osfmk/kern/zalloc.c:496
Backtrace (CPU 0), Frame : Return Address
0xffffff811662b910 : 0xffffff800c73a811
0xffffff811662b990 : 0xffffff800c77a590
0xffffff811662ba00 : 0xffffff800c779c17
0xffffff811662ba40 : 0xffffff800c778de7
0xffffff811662bb70 : 0xffffff800c720a3b
0xffffff811662bc40 : 0xffffff800c7337ff
0xffffff811662bcb0 : 0xffffff800c72b873
0xffffff811662bd00 : 0xffffff800cbb89e0
0xffffff811662bdc0 : 0xffffff800cbb6fc0
0xffffff811662be30 : 0xffffff800cbb8860
0xffffff811662bf20 : 0xffffff800cbb6627
0xffffff811662bf50 : 0xffffff800cc4dcb2
0xffffff811662bfb0 : 0xffffff800c83ac46
BSD process name corresponding to current thread: diagnosticd
Mac OS version:
14A389
Kernel version:
Darwin Kernel Version 14.0.0: Fri Sep 19 00:26:44 PDT 2014; root:xnu-2782.1.97~2/RELEASE_X86_64
Kernel UUID: 89E10306-BC78-3A3B-955C-7C4922577E61
Kernel slide:     0x000000000c400000
Kernel text base: 0xffffff800c600000
__HIB text base: 0xffffff800c500000
System model name: iMac11,1 (Mac-F2268DAE)
System uptime in nanoseconds: 24152197674
last loaded kext at 23160986348: com.apple.driver.AppleBluetoothMultitouch 85.3 (addr 0xffffff7f8e5df000, size 61440)
loaded kexts:
com.apple.driver.AppleBluetoothMultitouch 85.3
com.apple.driver.AppleHDAHardwareConfigDriver 266.5
com.apple.driver.AppleTyMCEDriver 1.0.2d2
com.apple.driver.AGPM 100.14.37
com.apple.driver.AppleMikeyHIDDriver 124
com.apple.driver.AppleHDA 266.5
com.apple.iokit.IOBluetoothSerialManager 4.3.0f10
com.apple.filesystems.autofs 3.0
com.apple.driver.AppleOSXWatchdog 1
com.apple.driver.AppleMikeyDriver 266.5
com.apple.driver.AppleHWSensor 1.9.5d0
com.apple.driver.AppleUpstreamUserClient 3.6.1
com.apple.kext.AMDFramebuffer 1.2.8
com.apple.iokit.IOUserEthernet 1.0.1
com.apple.iokit.IOBluetoothUSBDFU 4.3.0f10
com.apple.ATIRadeonX2000 10.0.0
com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport 4.3.0f10
com.apple.driver.AppleLPC 1.7.3
com.apple.driver.ACPI_SMC_PlatformPlugin 1.0.0
com.apple.kext.AMD4800Controller 1.2.8
com.apple.Dont_Steal_Mac_OS_X 7.0.0
com.apple.driver.AppleHWAccess 1
com.apple.driver.AppleHV 1
com.apple.driver.AppleMuxControl 3.7.21
com.apple.driver.AppleBacklight 170.4.12
com.apple.driver.AppleMCCSControl 1.2.10
com.apple.driver.AppleIRController 327.5
com.apple.driver.AppleUSBCardReader 3.5.0
com.apple.driver.AppleFileSystemDriver 3.0.1
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless 1.0.0d1
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib 1.0.0d1
com.apple.BootCache 35
com.apple.iokit.SCSITaskUserClient 3.7.0
com.apple.driver.XsanFilter 404
com.apple.iokit.IOAHCIBlockStorage 2.6.5
com.apple.driver.AppleUSBHub 705.4.1
com.apple.driver.AppleFWOHCI 5.5.2
com.apple.driver.AirPort.Atheros40 700.74.5
com.apple.iokit.AppleBCM5701Ethernet 10.1.2b3
com.apple.driver.AppleAHCIPort 3.0.7
com.apple.driver.AppleUSBEHCI 705.4.14
com.apple.driver.AppleUSBUHCI 656.4.1
com.apple.driver.AppleRTC 2.0
com.apple.driver.AppleACPIButtons 3.1
com.apple.driver.AppleHPET 1.8
com.apple.driver.AppleSMBIOS 2.1
com.apple.driver.AppleACPIEC 3.1
com.apple.driver.AppleAPIC 1.7
com.apple.driver.AppleIntelCPUPowerManagementClient 218.0.0
com.apple.nke.applicationfirewall 161
com.apple.security.quarantine 3
com.apple.security.TMSafetyNet 8
com.apple.driver.AppleIntelCPUPowerManagement 218.0.0
com.apple.driver.IOBluetoothHIDDriver 4.3.0f10
com.apple.driver.AppleMultitouchDriver 260.30
com.apple.driver.DspFuncLib 266.5
com.apple.kext.OSvKernDSPLib 1.15
com.apple.iokit.IOAudioFamily 200.6
com.apple.vecLib.kext 1.2.0
com.apple.iokit.IOSerialFamily 11
com.apple.kext.triggers 1.0
com.apple.iokit.IOSurface 97
com.apple.iokit.IOFireWireIP 2.2.6
com.apple.iokit.IOBluetoothHostControllerUSBTransport 4.3.0f10
com.apple.iokit.IOUSBUserClient 705.4.0
com.apple.driver.AppleHDAController 266.5
com.apple.iokit.IOHDAFamily 266.5
com.apple.driver.AppleSMBusPCI 1.0.12d1
com.apple.driver.IOPlatformPluginLegacy 1.0.0
com.apple.driver.IOPlatformPluginFamily 5.8.0d49
com.apple.kext.AMDSupport 1.2.8
com.apple.AppleGraphicsDeviceControl 3.7.21
com.apple.iokit.IOBluetoothFamily 4.3.0f10
com.apple.driver.AppleSMC 3.1.9
com.apple.driver.AppleGraphicsControl 3.7.21
com.apple.driver.AppleBacklightExpert 1.1.0
com.apple.iokit.IONDRVSupport 2.4.1
com.apple.driver.AppleSMBusController 1.0.13d1
com.apple.iokit.IOGraphicsFamily 2.4.1
com.apple.iokit.IOUSBHIDDriver 705.4.0
com.apple.iokit.IOSCSIBlockCommandsDevice 3.7.0
com.apple.iokit.IOUSBMassStorageClass 3.7.0
com.apple.driver.AppleUSBMergeNub 705.4.0
com.apple.driver.AppleUSBComposite 705.4.9
com.apple.iokit.IOSCSIMultimediaCommandsDevice 3.7.0
com.apple.iokit.IOBDStorageFamily 1.7
com.apple.iokit.IODVDStorageFamily 1.7.1
com.apple.iokit.IOCDStorageFamily 1.7.1
com.apple.iokit.IOAHCISerialATAPI 2.6.1
com.apple.iokit.IOSCSIArchitectureModelFamily 3.7.0
com.apple.iokit.IOFireWireFamily 4.5.6
com.apple.iokit.IO80211Family 700.52
com.apple.iokit.IOEthernetAVBController 1.0.3b3
com.apple.driver.mDNSOffloadUserClient 1.0.1b8
com.apple.iokit.IONetworkingFamily 3.2
com.apple.iokit.IOAHCIFamily 2.7.0
com.apple.iokit.IOUSBFamily 705.4.14
com.apple.driver.AppleEFINVRAM 2.0
com.apple.driver.AppleEFIRuntime 2.0
com.apple.iokit.IOHIDFamily 2.0.0
com.apple.iokit.IOSMBusFamily 1.1
com.apple.security.sandbox 300.0
com.apple.kext.AppleMatch 1.0.0d1
com.apple.driver.AppleKeyStore 2
com.apple.driver.AppleMobileFileIntegrity 1.0.5
com.apple.driver.AppleCredentialManager 1.0
com.apple.driver.DiskImages 389.1
com.apple.iokit.IOStorageFamily 2.0
com.apple.iokit.IOReportFamily 31
com.apple.driver.AppleFDEKeyStore 28.30
com.apple.driver.AppleACPIPlatform 3.1
com.apple.iokit.IOPCIFamily 2.9
com.apple.iokit.IOACPIFamily 1.4
com.apple.kec.corecrypto 1.0
com.apple.kec.Libm 1
com.apple.kec.pthread 1
Model: iMac11,1, BootROM IM111.0034.B02, 4 processors, Intel Core i7, 2.8 GHz, 8 GB, SMC 1.54f36
Graphics: ATI Radeon HD 4850, ATI Radeon HD 4850, PCIe, 512 MB
Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334548312D4346382020
Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334648302D4346382020
Memory Module: BANK 0/DIMM1, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334648302D4346382020
Memory Module: BANK 1/DIMM1, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334548312D4346382020
AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x8F), Atheros 9280: 4.0.74.0-P2P
Bluetooth: Version 4.3.0f10 14890, 3 services, 27 devices, 0 incoming serial ports
Network Service: Wi-Fi, AirPort, en1
Serial ATA Device: Hitachi HDS722020ALA330, 2 TB
Serial ATA Device: OPTIARC DVD RW AD-5680H
USB Device: Hub
USB Device: Internal Memory Card Reader
USB Device: BRCM2046 Hub
USB Device: Bluetooth USB Host Controller
USB Device: Hub
USB Device: IR Receiver
USB Device: Built-in iSight
Thunderbolt Bus:
I have a late 2009, 27" iMac, 2.8 GHz, 8gb Ram - was running Mavericks, upgraded to Yosemite
Ive run disk utility and verified disk multiple times - on one occasion it said the HD was corrupt but successfully fixed and hasn't reappeared since.
I've also run the hardware test (hold down D as computer restarts) with no problems found
And the ram reset thing (hold down R when computer restarts)
Ive also reinstalled Yosemite and clean Installed it so my computer is now empty.
I've also taken out each piece of ram and tried booting with each individual piece (the same problem occurred with each piece)

I am experiencing this same exact problem; however, I upgraded to Yosemite a couple of weeks ago and didn't experience any problems until this past Friday. The only other thing that's been done since then was installing some updated drivers for my daughter's Wacom Intuos Tablet. Everything was fine for a bit and then (as best we can tell), the video froze up on my son while he was using it and he walked away without shutting it down. We *think* it got overheated and appears to have resulted in the ATI Radeon HD 4850 now causing kernel panics during boot-up.
Symptoms:
On boot, the chime plays and apple logo appears and the progress bar begins to fill in until it gets about 1/4 of the way across.
After the progress bar gets about 1/4 of the way across, the screen goes gray/white, then black while the machine shuts down and re-starts
The machine starts back up and there is an error message (sometimes) that appears and says something went wrong during boot.
After a bit (or if I press a key), the whole cycle starts all over again with Step 1. above.
I've done the following, myself, to no avail:
Reset the SMC (unplug the power and all cables, wait 15-20 seconds and plug the power back in) - didn't help
Reset the NVRAM/PRAM - didn't help
Attempted to boot into Safe Mode - boots and then the display shifts to the left and has garbled/pixelated squares on the bottom right corner
Attempted to boot from the 10.6.2 DVD that came with the iMac when we purchased it back in November, 2011 - boots and then the entire display is pixelated/garbled
Ran the Apple Hardware Test (simple (5+ minutes) and extensive (1+ hours) - no problems found by either, but it didn't appear that the GPU was tested during this diagnostic
Verified that the EFI and SMC firmware is up to date with the latest for the iMac 11,1
Booted into the Recovery Partition (this is the only thing that has succeeded)
Recovery Mode: Ran the Disk Utilities to verify the 1TB HD - no issues with the disk or with permissions.
Recovery Mode: Created a .dmg of my entire 1TB Disk to a backup drive (No time machine backups...I know, bad practice on my part).
Recovery Mode: Attempted to re-install Mac OS X Yosemite - problem persists on reboot
Recovery Mode: Erased and Low-Level (1 pass) write of the entire 1TB partition on the HD and re-installed Mac OS X Yosemite - problem persists on reboot
When I attempt to boot into Safe Mode (Verbose: Command + Shift + V rather than Command + Shift), the messages scroll from the screen before I can catch what it's saying, but it appears to be stating that the machine is re-booting after a kernel panic due to display problems...which correlates with the garbled/pixelated display.
I've found a couple of other posts on here and they seem to point to the ATI Radeon HD 4850 and issues with it overheating and going tango uniform as well.
Basic Troubleshooting of Gray Screen Situations: Mac OS X: Gray screen appears during startup - Apple Support
Specific Troubleshooting and ATI Radeon Info: 09 27" iMac 2.66 grey garbled screen, no boot up   10.8.3. / Senior mods please
I've scheduled an appointment to take it into the Apple Store next Saturday (my first available) to have them verify my findings. I'm hoping and praying that it doesn't cost an arm and a leg to repair/replace the GPU...can't really afford it right now.
At any rate, I hope this information is useful to you!

Imac boot-up issue

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