17 digit MLB seems to be too difficult to crack...
Hence decided to try 13 digit MLB and 11 digit serial number.
- I chose iMac 11,3 (27-inch Mid 2010) system definition (latest iMac with 11 digit serial number). I chose a serial number (valid but not registered) from an early week of 2011. As far as i know, iMac 11,3 was produced till 17th week of 2011. Serial - W81ww***DB6
- For MLB week of manufacture, i chose a value one week earlier than serial number. W81ww****DF7Y (EEE code - DF7Y, ww - week of manufacture)
- For ROM, i chose 6c3e6d****** where the last 6 digits are from my ethernet MAC address.
Avoid letters 'I' and 'O' in serial number as well as MLB. Real Mac serials don't have these values as far as i know.
I noticed two issues with this system definition compared to using iMac 14,2 system definition.
- Mouse cursor lag for the initial 30-40 secs after boot. A process named 'Displaypolicyd' runs during that time.
- I am not seeing the usual options under Energy Saver in System Preferences. Power management may not be ideal compared to iMac 14,2. But have to compromise for iMessage and FaceTime. In fact, the lowest watt reached (in Intel Power Gadget) is same as before.
Other than these, i didn't notice any issue. Sleep, USB 3.0 work fine.
Had to contact Apple customer care with the customer code. FaceTime and iMessage work fine now.
Although 13 digit MLB will work with iMac 14,2 system definition, I chose iMac 11,3 as Apple may enforce further validation check anytime soon or later. Hope this combo will work longer...
EDIT (July12, 2015):
Regarding the cursor lag problem, it is not there in mavericks but will be there in yosemite with HD4600 graphics when iMac11,3 system definition is used. I solved this problem by adding iMac11,3 Board-ID [Mac-F2238BAE] to info.plist of AppleGraphicsDevicePolicy kext.