Is it possible to upgrade a Mac Pro (2007) with Lion (10.7) to Yosemite (10.10)? I have a MacPro (mid-2007) with the configuration listed below:


Processor: 2x 2.66Ghz Dual Core Intel Xeon
Memory: 20Gb 667Mhz - DDR2 FB-DIMM
OSx: Lion 10.7.5
NVIDIA Chip Model 1024Mb
SSD: 512Gb
HD2: 1Tb
HD3: 1Tb
HD4: 500Gb


I've been searching how to upgrade to Yosemite directly, but I found he is not compatible anymore (only MacPro 2008 / later). There's a way to hack/workaround this problem? And why I can't upgrade my Lion to Yosemite if the hardware specs are totally compatible?
OK, this might be somewhat opinion-based, however...

Possible, yes.
Worth it, no.

Possible
There are tools &amp; online guides far too long to repro or précis here on how to achieve it. It requires hacking the firmware &amp; needs re-hacking at each update -
These guides from MacRumors are as good as they get, one for Yosemite &amp; another for El Capitan.

Worth it?
The 1,1 &amp; 2,1 are really end-of-life &amp; now very slow compared to a 'modern' machine.
I really guess it depends on your budget, but you can get an absolute top-flight 5,1 [or the smart money goes on a 4,1 with the Apple upgrade kit] with two 6-core hyperthreading Xeons @3.46GHz &amp; 64GB RAM for under £1800 in the UK. Your existing drives will just carry over [though idk about the OS itself, mine did from a 3,1 to 5,1].
The Geekbench scores on those are about 32k, that's slightly under the current top model 'trash-can' at 33k. I just checked the score for the 2.66 Mac Pro, 6k.

I took the latter path, even though I was only moving up from a 3,1 - which is now in the hands of my partner &amp; very happily running El Capitan. I wanted a speed boost &amp; the upgraded 4,1 was right on the money for me.