Chosen Solution
My Mac suddenly faced a graphics issue after a week of RAM upgrade from 4 to 16 gb(CRUCIAL memory made for Mac) and it crashed. I took my Mac for repair to apple centre and they changed MBP’s MLB twice under the quality program as it was a manufacturing defect as per them. Also, as per APPLE test the Samsung SSD I have installed shows a SMART test failure (although no such failure is indicated by Disk utility or third party application). To remove this apprehension I sent the SSD to samsung for repair and as per Samsung there was no fault in the SSD. Even now the test is failed, that might be because MBP 2011 officially do not support SSD. Since then everything is working fine except a colorful line(attached) that comes while reboot (this came especially after PRAM reset that I performed after my MacBook was repaired. Its been more than 2 months that these lines show up ( picture attached), however, the Mac is working just fine. I get a boot time of not more than 20 seconds. Graphics otherwise with movies etc work fine. I want to know whether such line is normal or an abnormality as no one at apple seem to know about this issue accurately. I would appreciate a reply from you. Update (12/28/2016)
this is the image of the issue
My first educated guess on the hard drive issue is well know around here and with Apple (they just don’t admit it). It generally the hard drive/IR cable. It gets damaged as it comes over the last step on the case. Most knowledgable repairmen will replace it with the 2012 cable and put pads on either side of the cable. This new cable has a wider data path and can handle the higher speeds of an SSD drive. See the difference in just width: MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable MacBook Pro 15" Unibody (Mid 2009-Late 2011) Hard Drive Cable I probably replace three of these a week and always keep a good supply in stock. If a defective cable is left in place to long, it can destroy the hard drive. \Heres how to replace it, some times there are issues with the location on the tiny screws which hold it place when replacing with the 2012 cable: MacBook Pro 15" Unibody Early 2011 Hard Drive/IR Sensor Cable Replacement As to the colorful line that appears during boot, that is normal on several machines. It started showing up with El Captain. The Apple people generally are not real techs and they do not see it because they don’t work on the machines and the answer is not in their script ;-) It happens when the graphics drivers are loading.
I have only ever seen that line appear on 2011 15" MacBook Pro’s, usually a while before the GPU fails on them. Most of the time, it appears and the MacBook proceeds to boot fine, but sometimes it shows this and crashes. I have never seen this line appear on any other model, only on the majority of 2011 15" MacBook Pro’s I receive. If I ever saw this (last year, before the end of their repair program), I told the customer to take it to Apple ASAP, to ensure the GPU doesn’t fail on them. It may work fine, but it may get worse in time. Apple’s description of the GPU fault in their repair extension program mentions distorted video, which is what you are getting on boot. Regarding SSD, just sounds like Apple is trying to make excuses or something ;)
