StraitenedOut wrote:
Sorry. I thought I was being clear but maybe not clear enough. I really like everything about the iMac except its performance so I was looking for advice on upgrading by keeping the monitor, keyboard and touchpad but adding……..?something? Are there alternatives to adding the Mac Mini?
There are no hardware upgrades for your 27" 2010 Mac that would let it run any version of the operating system that is more recent than High Sierra.
You can expand RAM all the way to 16 GB (official limit) or 32 GB (actual limit). You can add external USB drives and Firewire drives – but the USB ports only run at USB 2 speeds, and there seems to be only one place that still carries Firewire 800 drives and enclosures these days. (That would be Other World Computing.). Even the SATA bays run at 3.0 Gbps (SATA-2 speed) instead of 6.0 Gbps (SATA-3 speed), which could limit the performance of an internal SATA SSD.
I would be surprised if there was any practical way to upgrade the CPU or GPU that made sense at this late date. Those were never user-upgradable.
----------
Your Mac supports Target Display Mode using DisplayPort input.
iMac (27-inch, Mid 2010) - Technical Specifications - Apple Support
"27-inch models also support input from external DisplayPort sources (adapters sold separately)"
If that was all there was to it, you could use your iMac as a Target Display for a current Mac with the aid of a USB-C to Mini DisplayPort adapter cable. Unfortunately, Apple added restrictions on the video source. Now it has to be another Mac, released in 2019 or earlier, running Catalina or earlier. No current Mac supports using your iMac as a Target Display.
Use your iMac as a display with target display mode - Apple Support