I have a late-2011 Mac mini (2.7GHz dual i7, 8GB RAM, 1TB SSD) hooked up to a Thunderbolt display. In Mavericks, it ran wonderfully. In Yosemite, it runs horribly. Pretty much everything in the UI is slow and laggy; I type pretty quickly (80WPM normally, 100+ when I'm really going) and Yosemite seems to be only able to handle a few characters per second. This is happening in pretty much every application, where me typing at a normal speed will cause a pretty bad backlog of characters that slowly appear on screen - or sometimes characters will even be dropped.
Setting "reduce translucency" helped somewhat, but I suspect that the combination of the large monitor (2560x1440), the underpowered GPU (Radeon 6630M), and the system being old and probably not a standard test platform for them are probably why this isn't running so well.
Even when my system is sitting idle, WindowServer is taking a good 20% of the CPU time according to Activity Monitor (obviously Activity Monitor's refreshes would cause SOME usage there, but 20%?) and when an application is doing really poorly, it can jump up as high as 90%.
On the other hand, it runs great on my late-2013 Retina MacBook Pro. No regrets there.
Setting "reduce translucency" helped somewhat, but I suspect that the combination of the large monitor (2560x1440), the underpowered GPU (Radeon 6630M), and the system being old and probably not a standard test platform for them are probably why this isn't running so well.
Even when my system is sitting idle, WindowServer is taking a good 20% of the CPU time according to Activity Monitor (obviously Activity Monitor's refreshes would cause SOME usage there, but 20%?) and when an application is doing really poorly, it can jump up as high as 90%.
On the other hand, it runs great on my late-2013 Retina MacBook Pro. No regrets there.