Bad Information on this topic begins with the model description at the top of the page! The 2012 A1278 MacBook Pro doesn’t have DDR5 video RAM since it uses Intel HD4000 graphics that shares system RAM for video. Mine shows 1536MB of video RAM with 8GB of RAM installed.

I use an earlier iMac temp sensor that mounts externally on the hard drive. They have to be rewired to the logic board connector and then they work perfectly fine without a fan control app. It is Apple part no. 922-8165, the clip that holds it is part no. 922-8183. Should be able to get them for well under $10.

SATA is SATA. Apple has no special magic here. SATA is an international standard. SMART is another standard that has always worked by reading hardware data about the drive via the data connection (PATA or SATA). My Asus P8Z77 motherboard shows me a wealth of info about my drives this way: Since I'm an Independent Mac tech I don't typically see many Macs that are still within their Apple care timeframe. I have yet to do anything but software work on the late 2012. My previous comments were directed at the earlier iMac models. If I owned your iMac I'd simply try a different drive. In OWC's video on RAM upgrades you can clearly see the Hitachi 1TB drive which doesn't have any Apple branding on it at all. My Guess is that you'd be safe with any Hitachi drive as a replacement, but I'd also bet that any drive would work with no special steps needed. BTW I'm a beta tester for a major hard drive manufacturer and their replacement 2.5" 'Fusion' drive is in beta right now and is performing about midway between...

I have used the sensors from earlier iMacs as well as from Macbook Pros. The Macbook Pro aluminum models are the ones I usually use. There are several of them, I usually use the ones that are under each fan. They have 2 leads just like the iMac which I extend to reach the drive. Then i attach the sensor with double-sided tape (same stuff we use to adhere glass on iPads and unibody MacBooks). The sensors from earlier iMacs (if they are the 2 lead type) also work. Some splicing is usually required. I have done it this way since the very first drive replacement I had to do on one of these iMacs. I don't think that any resistor or jumper is a good idea at all. Temperatures in a computer need to be monitored and the fans adjusted continuously for everything to work at peak efficiency. I don't want to leave fan control up to my clients to monitor. Nor do I want their iMacs running noisily because their fans have to be run at high speed all the time. I'm perfectly willing to hack and modify things when it makes...

I have an Independent Apple repair business here in Oregon. This issue is really not an issue. Apple was not trying to prevent anyone from replacing hard drives. Apple was trying to save money by using the built in sensor in the HDD instead of adding their own external one. I have used many other temp sensors from other Macs for this. My reasoning is that if I have to alter the cable I may as well make it easier on the next tech by adding an external Apple temp sensor from another Mac. The temp senders Apple uses are surprisingly standardized. I have checked them with an infrared thermometer and they appear to have similar specs.