Hi, I’m looking for a Mac Pro and I found somebody who is selling one... My expertise aren’t very good, so my question is if I’m making a good buy...
It’s a Mac Pro 2.8Ghz 24mb cache octa core 500GB SSD 32GB RAM ATI R9 2GB
It depends on what you want to use it for and what the asking price is. As already mentioned it appears to be a 2008 or possibly a 2006 / 2007 model. Whatever it is it's not a standard offering from Apple as they did not sell a 2006 / 2007 model with a quad core 2.8GHz CPU nor did they sell the 2008 model with PC5300 FB-DIMMs. It's possible either the CPU was upgraded in a 2006 / 2007 or the slower memory was used in a 2008 (not uncommon). Neither year had the ATI 5770 which was a 2010 / 2012 stock graphics card.
What you have listed, if I am interpreting the information correctly, shows it's not a standard offering from Apple and, without more information, I cannot provide specific advice as to that systems capabilities.
Generally speaking a 2009 and later model Mac Pro is desirable as they're currently supported (2009 with a firmware update) and the best architecture for the 2006 - 2012 series. The least desirable are the 2006 and 2007 models as they lost OS support a long time ago (with the release of Mountain Lion back in 2012). In between is the 2008 model which is very similar to the 2006 / 2007 models but, relatively speaking, just lost OS support (with the release of macOS Sierra in 2016).
My recommendation is to inventory the software you need / want to run and see the minimum OS version it requires. That right there can disqualify certain models.
The one in post #12 is a nice system. Keep in mind it says it's a 5,1 (i.e. 2010 or later) but it's really a 4,1 (2009) upgraded to a 5,1 via a firmware update. Software wise an upgraded 4,1 is essentially equivalent to a true 5,1 but the distinction is important if you decided to upgrade to 12 cores.
Unless the year they posted is incorrect, 5,1 machines were from 2010 onward. It could be a 2009 computer that's been flashed with 5,1 firmware though. Good tower but a better GPU would help a lot. You could probably do some editing on it in HD, but 4k would likely be difficult if not impossible... Correct me if I'm wrong?
Well, I think you are getting your cart ahead of the horse here. What are the requirements of your editing process? Once you have sorted that out, then you can determine what computer will meet those needs.
IMHO the cMP is not a good choice for people who aren't already very familiar with it (or willing to take the time to read and learn a lot on their own). IMHO you would be better served with an iMac, or wait a couple of weeks to see if Apple announces a new Mac Mini--there are reliable rumors that they will. Both the 2017 iMac and the new Mini if it comes, have the ability to use an eGPU to accelerate video editing tasks in FCPX. Both machines will have way faster single-core performance than the cMP, simply because they are using much newer processors.
The cMP is a venerable machine but it is old now (9 years!) and while it is still technically supported it needs hardware upgrades to even approach the capabilities of current Macs. At this point it's really better suited to enthusiasts and computer people who like to tinker with it. It is definitely not a turn-key type machine.
Depending on your budget, this could be a good system. You will need to check the HDD - if it's over 5 years old, as a rule of thumb it's better to replace it. High Sierra is the last OS supported by this configuration. You'll need an upgraded graphics card ($100-$270) to get to Mojave. The 5770 edits HD fine.
As stated above, this system is old, and 10.14 may be the last OS which officially supported. A newer iMac should last a lot longer.
Also, it's a 4,1 that was firmware upgraded to 5,1. Not that there's anything wrong with that. Looks like it's a single CPU.