iMac has started often freezing up

[pedalmasher]

I am starting to feel like I am pack in the dreaded world of Windows. Since "upgrading" to Yosemite, not only has Aperture started taking about a minute and a half to load - it used to load quite fast, but I am suffering at least three complete system freezes daily. The mouse pointer will stay active, but everything is dead. Nothing can be activated requiring a complete, long, re-boot. I am about to cash it in on Yosemite an revert back to a system that allowed everything to function normally and quickly. Interestingly, my Memdiag program always shows plenty of usable memory when the system freezes so it is not a function of that being jammed. Any suggestions appreciated. There is a possibility that Aperture might potentially be a culprit in that as an avid, very active photographer, it is often running in the background during the day.

 

[diipii]

Overheating especially the graphics card. The next symptoms will be corruption of parts of the screen and audio continuing while picture freezes followed by total system freeze. All of these events are caused by the slim cased design not allowing enough cooling air to circulate. I have never heard any older tower Mac suffering any heat problems even in the most graphic intensive situations.

 

[pedalmasher]

Overheating especially the graphics card. The next symptoms will be corruption of parts of the screen and audio continuing while picture freezes followed by total system freeze. All of these events are caused by the slim cased design not allowing enough cooling air to circulate. I have never heard any older tower Mac suffering any heat problems even in the most graphic intensive situations.

Sounds right except mine is an older, thick cased iMAC,

 

[fathergll]

I am starting to feel like I am pack in the dreaded world of Windows.

Unless you specifically have a good reason, it's almost never a good idea to upgrade to a brand new OS. It's not just a Windows thing....it's all software.