Thanks again! You're right, I'm "new to it" (looked at an hour long "how to" video to swap out the HD, and not sure I want to tackle that?), but I've been running a Mac since about 1987, initially on the 9" screen Mac at work with a slightly more capable desk top machine at home (all of a 40 MB HD), and several others since. I purchased this iMac in early 2014 just before I retired, with as much capability as I could get. It's the original configuration with the exception that I've upped the RAM to 32 GB.
Oooh. You have the 27-inch variant. Nice! The 21.5-inch variant, the one I have, can also have RAM upgraded, but caps out at 16GB and requires opening the front glass the same way one gets at the hard disk drive (i.e., the iFixit steps linked in my previous reply). The 27-inch has that handy RAM cover on the rear which makes access a lot easier.
That said, I've been running Big Sur for a little over a year now with no problems except for the software incompatibility discussed which you said I shouldn't be able to do.
That’s impressive and interesting, honestly.
This may be a situation in which Apple devised a way to prioritize system file access/use to the SSD blade portion (more on that in a sec), and reserved the lesser-accessed files (like personal/user files) to the HDD.
I mean, this is how “Fusion” was envisioned to begin with, but Fusion also came about (the Mavericks era) well before the arrival of APFS (High Sierra and up).
I think I do have a solid state HD (APPLE SSD SD0128F, see below graphic), or is that the "blade" you mentioned?
Yes. Correct.
The late 2013 iMacs shipped with a receptacle for the Apple version of the NVMe/PCIe SSD blade (in 2014, to save costs, Apple didn’t populate the receptacle on the main board for units which were not ordered with Fusion drives, despite the contacts on the board still being present). Fusion-equipped models actually use the receptacle; models like mine, which shipped only with the HDD, have the receptacle, but is empty.
That’s the “blade” in question. The form factor of an NVMe SSD — whether the standard m.2 or the proprietary Apple-style — looks like a thin “blade”. In this case, the “blade” is 80mm (8cm) in length — or, size “2280” (they also come in “2242”, “2260”, and even a very long “22110”, with 2280 being most common).
Here’s a standard m.2 NVMe SSD form factor:
Here’s an Apple version with proprietary connectors:
Here’s an inexpensive adapter which enables one to use a standard m.2 blade with the Apple-proprietary receptacle found on the rMBPs, MBAs, and iMacs of ca. 2013:
If my "Fusion" drive is a SSD, am I then configured (see 2nd graphic) to proceed with the OCLP upgrade to Ventura (Sonoma??) without doing the drive partitioning you mentioned earlier? Delete the "Patched Sur" from my applications folder?
View attachment 2358483
So yes, it looks like your iMac shipped with the 128GB SSD blade (more accurately, 121GB, with 7GB “over-provisioning”, which is a common feature for SSDs of all kinds) alongside a 3TB HDD. Your system reports “3.12 TB” because it has the 3TB HDD + 120GB SSD combined in “Fusion” configuration. To your system, outside of Disk Utility, your “Macintosh HD” is one
logical drive.
Since 2013, the cost of much higher capacity NVMe SSD blades have come down
a lot — to the point where picking up a decent, 1TB SSD blade (with on-board DRAM), plus Apple connector-adapter, can be done for less than USD$90 (and that’s regular price, with sales being frequent). It’s very much doable. Heck, that alone might be all you’d want if you are thinking of doing a step-by-step upgrade at some point. Add in a 2.5-inch SATA SSD — available in increments of 1TB, 2TB, 4TB, and 8TB — to replace the 3.5-inch HDD, and you’d be set for the rest of the iMac’s long life to come.
[Yes, I’m on team “SSD everything” to eke the most — and best — performance on vintage Macs, so I admit that bias. Heck, I upgraded my PowerPC Macs with SSDs, and even on those much slower PATA buses, it made a significant difference.]
If you do, ultimately, pursue an SSD drive upgrade, pick up a copy of Carbon Copy Cloner to clone your patched Big Sur, if you want to keep your settings/configurations/etc., to an external drive drive before changing the internals.
Then, after the new SSD(s) are in place, you should be able to clone that back to internal storage. From there, you can then upgrade the patched Big Sur to Ventura or Sonoma. Or, you can install an OCLP-patched Ventura/Sonoma fresh on the new internal drive(s).
I hope I haven’t overcomplicated your options and planning here, but this kind of upgrade will be well worth your while in the long run.
