Will It Work on Leopard: iMac Late 2009 with Quad Core i7, 8GB and 4850 Mobility GPU

10.6/Snow Leopard is the earliest OS that'll run on the late 2009 iMacs.

It depends.

I got my late 2009, 27 iMac to run OS X 10.5.8 Leopard off of an external FireWIre hard drive with no issues.

I had this OS version cloned on this external hard drive for my older PowerMac G4.

It boots very quick and the short times I was using this on my 2009 iMac, seemed very stable and responsive.

My original OS X version for this iMac was OS X 10.6.1.

My thinking was the the hardware might except running the last update version of 10.5 Leopard.

You won't be able to install this to your iMac's internal hard drive and run it from there, but I can say for sure it will run from a fast FireWire 800 external hard drive and it is blazing fast on this model iMac.

Much, MUCH faster than even OS X 10.6.8 Snow Leopard.

You would need to try it and see what happens.

My iMac is just the single 3.06 i3 CoreDuo2 CPU, though. I do not know if this will be a factor or not.

Just in case no one believes me here are two images I took from my iPad late tonight running OS X 10.5 Leopard on my late 2009, 27 inch screen iMac.

The only issue I have found is that the there are no additonal display resolution settings to adjust.

So the iMac is stuck with its native resolution in OS X 10.5.8 Leopard (I hate the iMac's 2550 x 1900 resolution. Everything is just too small for my 50 year old eyes.)

You can adjust the size of icons and icon text size in the Finder Prefs and View Options, you can adjust the Dock size, but that is pretty much it.

No way to adjust the size of the text in the top main menu bar or make the text in the title bar on Finder windows larger, either.

But everything else works.

I can access all of my other external drives, most of the applications, that are mostly updated to work just with OS X 10.5.8 Leopard, launch and work fine. My Wacom Intuous3 tablet seems to work fine add I can adjust the preferences and controls of all of by pens and airbrush tool.

My older IR Microsoft and Logitech mice work fine.

I can't believe how much faster OS X 10.5.8 runs on this iMac.

If I hadn't updated all of my Apple apps on OS X 10.6.8 Snow Leopard and all my updated iTunes, iPhoto and Aperture Libraries, long ago, needed more up to date web browsers (TenFourFox wasn't available back in 2011) and Mail clients, more up to date Flash and security updates, I might have just stayed using OS X 10.5 Leopard on this iMac.

It is quite a bit faster than Snow Leopard. Even that much faster considering I am running OS X 10.5.8 from my external FW800 drive.

Thanks for the info, I didn't think about a cloned drive from another earlier Mac, was just thinking about trying to install on the Internal drive, so I learned something again! 🙂