iMac Intel 27". EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz), EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz)

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Video Corruption after Clean Yosemite Install

Interesting problem here. We've got a really clean 27" iMac in the shop, it tested beautifully for all tests in AHT. Yosemite installed with no problems at all, smooth as silk.

All was well until Monday when we noticed corrupted video after boot up. What's strange is that video is perfect on Safe Boot or when booting from installation media, so it's definitely not hardware related. Creating a new user account also results in corrupted video so it's not a specific user setting either. We recently had similar graphic driver issues with a Mac Pro that was corrected by installing Nvidia's drivers for OSX. This iMac has an ATI Radeon HD 4850 PCIe graphics card and ATI doesn't offer drivers for OSX, so the same fix won't work for the iMac.

Any thoughts? Is there a driver for this card somewhere that I haven't found yet?

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I have the exact same issue with the exact same machine. Safe boot works. But when booting normally i only see a white screen with the cursor. Remote desktop still works though. Really strange.

Called apple and they said i should have kt checked out.. But seems to me it has something to do with the video drivers..

Has anyone a fix?


A reflow of the GPU did the trick! Seems like it's a hardware problem after all.

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I could have something to do with the video acceleration? When i load ATI drivers from snow leopard the machine works but with very slow and ugly graphics..


What is "a reflow of the GPU"?


This is when you re-melt the solder used to hold the GPU to its electrical contacts.

Frankly, just re-heating the solder joints only offers a temporary solution as the solder will re-crystalize again from the heat of the GPU altering the state of the solder back to the non-conductive state.

If you remember your chemistry all it takes is a few crystals to act as a seed for the rest of the solution to re-align into joined crystals. Which is the exact problem you face here.

What really needs to be done is clean off all of the solder on the part and logic board pads and apply fresh heat resistant solder. That way no traces of solder which had gone into crystal form act as a seed.

This is not a DIY project to do it correctly. You do need the proper tools, materials and skills. While I understand it I don't even try to do it any more.


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Boy.. do I have a story for you.....the full specs on my barely used 27" iMac (late 2010) model.. fully loaded are shown listed at the end of this RANT

I have a fully loaded 27" iMac (late 2010) model.. and have been dealing with various video artifacts, manifestations and video corrupts and system kernel crash issue you talk about for years now


I bought the unit at the Apple store in Calgary, Canada (I live 2 provinces over) in Late january of 2011 with 8 Gigs of stock Apple RAM.

I did NOT buy the Apple Care extended warranty at the time.. was thinking I would buy it later since you have a full year to buy Apple Care 3 year extended warranty. *** MISTAKE ***

Took it home, but didn't even open it up for 6 months.. just left it in the box in my home office.. clean, safe room temp and environment.. sealed in box.. life was in flux at the time and so had no time to set it up.. had my 2010 MacBookPro anyways that I was using..

. anyways..

I Finally opened it up in Summer of 2011.. and this is where all the DATES become important.. because I have a theory on this problem (and its backed by many other internet ranters on this issue)

Now the base OS that shipped on Mid 2010 iMac 27" models was OS X v10.6 Snow Leopard that defaulted to 32bit kernel mode.. (but did support a 64bit kernel if you were inclined to switch it over) but not all apps worked great yet!.. so let it be @ 32bit kernel mode.. (The default)

I used the system briefly with Snow Leapoard Summer of 2011 and EVERYTHING was perfect with it.. I used it full time at work for Software Development using VMWare Workstation to host Windows both window and Linux VM's at the same time.. and worked it to the bone.. and the thing was rock steady.. not a single thing was wrong with the unit. I was VERY IMPRESSED.. I dumped Windows and Dell for life....

Then Apple released OS X v10.7 (Lion) in July 2011.. but i held back and stuck with Snow Leapoard due to all my VMWare stability requirements.... I usually wait at least 6 months for OS updates to stablize before updating on my Dev machines for work... to risky...

during my wait for Lion bugs to settle down.. in early 2012 i decide to upgrade my ram from first 8Gigs to 16gigs.. and then to 32Gigs of RAM (Crucial Mac RAM; all up to spec).. because OWC testing shows that even though Apple only formal supports 16 Gigs.. the system actually works fine with 32Gigs...

And things were still GREATfor me on Snow Leapoard...with my 32Gigs of ram and 32bit kernel

Then Apple released OS X v10.8 (Mountain Lion) in July 2012 (For Free).. so I decide to take the plunge and upgrade first from Leapoard to Lion (had to pay)... which was required in order to upgrade to Mountain Lion via the App Store... then did the upgrade to Mountain Lion.. which also forced the 64bit Kernel on to me.. which I was fine with.. preferred that anyways since most apps were 64bit in 2012.. (Except Chrome and few utilities)..

.. and all of the SUDDEN.. problems started happening...any time i played a You Tube video.. or Apple Quck time movie.. or even more simple then that.. the Magic Mouse Animations in the Mouse Preferences from Apple would CRASH my Video system and freeze my display.. i would have to SSH into my box from my linux computer to force the system to "reboot now" to at least not corrupt my Virtual Machines that were running.. the Kernel and Networking was Fine. .but the video would always fail the GUI and mouse....

So i'm thinking... Hey.. since it a 64bit Kernel.. and so much has changed... it MUST be my 32gigs of RAM... so I end up doing TONS of RAM and System tests in Safe Mode.. and Single user Mode.. and even test the ram in other computers.. NO issues with the RAM.. so i put back the Apple Certified 16 Gigs ram.. and even THAT did NOT fix it...

Huge ATI Video Problems..

I live with the issues.. and start researching.. I find TONS of other Mid 2010 27" iMac owners like me with the same issue with their ATI Radeon 5750 Cards and video corruption and kernel panics.., etc.

I start thinking.. how can my Video all of the sudden start failing.. its been rock steady for 2.5 years.. and ONLY after i Upgrade OS X from 32bit to 64bit with new Video Drivers to I get these issues..

Others say if you Bootcamp into Windows7.. download the ATI BIOS Driver tools for Windows.. you can tweak the ATI Video card BIOS power saving settings to be LESS aggressive and it will fix things.. worked for some.. but NOT me..

So I say.. ok.. it must be buggy drivers with 64bit Mountain Lion.. so I start submitting TONS of apple crash reports to Apple with full details.. and theories ... and think.. hey they will fix this in one of the future updates...BUT NO....

Then Mavericks comes out.. and i'm thinking.. finally they will have this fixed.. but NO!

The Yosemite Comes out.. and still NOT FIXED.

So I decide to take the off warranty unit to Apple Store for off warranty repair.. giving in to the idea that its a Hardware issue..... Apple replaces the Video card with a "new" one and i allow them to wipe my machine clean with Yosemite.. and they claim tits fixed.

I bring it home and 24 hours later.. the same Video corrupts.. except it doesn't crash my system.. just puts lots of corrupt pixelated images on the screen....

So I bring it back under the 90 day warranty for past warranty work.. and they claim there is NOTHING wrong with the Hardware.. so they wipe the machine and clean install Yosemite (Virgin apple install.. no 3r party software or hardware).. and they claim its fixed. they put it through TONS of hardware tests and video and animation tests.. and they don't see the issue.

I bring it home TODAY (April 1st, 2015).. and fire it up.. and the first thing i see is corrupt pixelated VIDEO.. when i open the preferences windows.. NOTHING installed.. pure virgin Yosemite on my Mac. no 3rd party software OR hardware plugged IN..

SO.. either my Mainboard is &&^&@@... And Apple store people really don't know how to diagnose and "FIX" things.. OR.. my better theory is that this IS a video driver problem in combination with flakey ATI Video Hardwarew, BIOS settings or Video RAM on ALL 2010 ATI 5750 Video Cards for 2010 27" iMac computers.

I find it very interesting that Apple recalled 2009 iMac models both 21" and 27" models as well as 2011 iMac models for the exact same type of Video problems..

BUT Apple NEVER recalled the 2010 models...

I bet its because not enough 2010 models were sold.. so they are shoving us under the BUS with a nice &&^& you!


Of the 5 years I have owned that 2010 27" iMac.. it has only been used as an actual computer for 1.5 years (first 1/2 year in box).. and the remaining 3 years it was used as an external Monitor for my MacBookPro workstation.. since i kept thinking Apple will one day fix their ATI drivers..

P.s. So now I have a 2014 MacBookPro and I use my $3500 27" iMac as a 2nd Monitor and VM hosting machine..

I wil NEVER EVER buy an iMac computer again.. Only their MacBook Pro's.. so now what i do is I only buy REFURB Apple Store online product. and take the savings use that money to buy the 3 year Apple Care... NEVER AGAIN!

Hardware Overview:

Model Name: iMac

Model Identifier: iMac11,3

Processor Name: Intel Core i7

Processor Speed: 2.93 GHz

Number of Processors: 1

Total Number of Cores: 4

L2 Cache (per Core): 256 KB

L3 Cache: 8 MB

Memory: 32 GB

Processor Interconnect Speed: 4.8 GT/s

Boot ROM Version: IM112.0057.B01

SMC Version (system): 1.59f2

Serial Number (system): W803902XGXU

Hardware UUID: 82A37CB3-9C4C-5419-AB7C-CEBFA515E54E

ATI Radeon HD 5750:

Chipset Model: ATI Radeon HD 5750

Type: GPU

Bus: PCIe

PCIe Lane Width: x16

VRAM (Total): 1024 MB

Vendor: ATI (0x1002)

Device ID: 0x68a1

Revision ID: 0x0000

ROM Revision: 113-B9710C-238

EFI Driver Version: 01.00.417



Display Type: LCD

Resolution: 2560 x 1440

Pixel Depth: 32-Bit Color (ARGB8888)

Main Display: Yes

Mirror: Off

Online: Yes

Built-In: Yes

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Links to this issue

and follow up

Lots of links in the above article to Apple own support Forums on HOW bad apple &&^&@@ us on this issue!

I'm a professional Software Engineer with an Electrical Computer Engineering Degree... since 1995 and I know my $@$* when I see it!..

Apple Store Genius Bar Staff and Service Techs are hacks at best.. OR Apple is just telling them to "indulge" us and make us go away.. since our $3500 compute is already 5 years old!..

every one of my Dell laptops lasted me 10 years.. and every one of my Grey Box home made Intel Windows PC's last me 10 years Minimum!!

Apple.. this whole thing you state that in order to make Good Software.. you have to Make Good hardware.. is BULLSHIT.. and apple is so use to eating their own $@$*.. they have convened themselves that it tastes Good....

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Tranquil Computer will be eternally grateful.
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