For the past few months, my mid-2011 27" iMac has been having graphic issues. It would occasionally fill the screen with various patterns of small squares that blinked on and off. The only way to get rid of them would be to drag a window around, "erasing" them. After a few occurrences of this happening, I knew I needed to reboot to avoid a system lock up. This is similar to a graphics card issue I had fixed under warranty in 2012.
So when it began occurring more often, I knew certain death was only a matter of time. My plan was to wait until it croaked, and then replace it. But our daughter is home from college for Christmas, and I found the educational discount is $200. Hmmmm, wait, or preemptively buy a new iMac. Financially, I really didn't want to buy now, what with Christmas bills, a couple of car payments, etc. Then I looked at Gazelle and found I could sell it in running condition for $435. That sealed the deal! I had an older MacBook Air and 17" MacBook Pro laying around, and those added another $311 to the Gazelle deal! Now we're cooking! A total of $946 in "found" money!
The replacement is the best of Apple's "Good-Better-Best" standard offering 27" iMacs. The 27" Retina 5K iMac w/2T Fusion drive and 8 GB of RAM. I ordered two 16 GB sticks from OWC to bring the total to 40 GB of RAM. Here's what we bought on Thursday.
https://www.apple.com/shop/buy-mac/imac?product=MNED2LL/A&step=config#I've spent large parts of the last several days carefully bringing things over from the old iMac. Well, actually, from the CCC backup on an external FireWire 800 drive, because I can directly plug it in and move files much faster. Where possible, I've been reinstalling as new, and only copying the preference files over. I really want to avoid bringing a bunch of orphaned files just because I don't know what they are, so I'm taking my time. As of this evening, the only things I have running on the old iMac are Twitter with seven accounts, and my Logitech 9000 webcam, which feeds my SkyCam on my weather web site. Works fine plugged into the old Mac, but nothing on the new one.
As far as WeatherCat and supporting files/software/hardware are concerned, I'm in pretty good shape. I initially couldn't get the SiLabs driver to stick, but finally solved that. I had to re-enter all of my server/FTP/and weather account passwords, and somewhere along the line I lost my UK Met Office WOW credentials, and their new login doesn't work. So I'll stop uploading there. And the above mentioned SkyCam. That's it! Everything else works great!
And the best part, is since this is a Fusion drive, it came loaded with Sierra and not High Sierra! Yippeee!