TechRepublic's Editor In Chief Jason Hiner does not feel you should put Windows 8 on an older PC unless you are a technophile.
He underestimates the power that this fully operational upgrade represents.
While I personally recommend that the upgrade not be done on anything older than say, a 2008-era system with 4GB of memory in order to see the best results, it's possible that some systems that are substantially older may benefit.
I myself installed it on a 2006-era Opteron system (which had a BIOS update in 2009) and it works fine. I've never seen Windows run faster, as a matter of fact.
Other end-users with older systems might see similar results, but their mileage may vary.
If your system is so old (Read as: Pentium 4 and AMD64 released earlier than 2004) that it has a CPU which does not support the NX processor bit, Physical Address Extension (PAE) and Streaming SIMD Extensions 2 (SSE2) then you can consider that a hard stop for Windows 8. You need a new computer, really.
But perhaps you fear what installing the software could do to your old computer even if your hardware is compatible. Perhaps you remember what the Vista upgrade did to your PC.
Do not worry my Sith Learners, I want you to feel comfortable with the embrace of the Dark Side.
Vista was a perfect storm for a disaster in many respects because a lot of hardware changes occurred in the industry when it came out, Microsoft had a lot of problems getting it out the door due to disruptive re-orgs that went on during the development process, and most end-users and even the OEMs were completely unprepared for it.
I think most PC experts would definitively agree that Windows 7 was a significant improvement over Vista.
That being said, the preponderance of PC hardware that has been in general circulation since 2007 or so is very well equipped to handle Windows 8. There's no way in hell this upgrade is going to be another Vista strictly from a hardware compatibility perspective.
This is because there's been a lot of consolidation in terms of components used since Vista and Windows 7's release, and Microsoft has had that much time to integrate all the necessary 3rd-party drivers into the core stack.
I feel that enough improvements have been incorporated into the new OS that there is a very real performance increase on hardware that has been released in the last four years, and that also includes very recently purchased PCs. Bootup time is substantially better and the kernel has been better optimized for use with SSDs, for example.
To me those improvements are definitely quantitative.
With Windows 8, we're talking anywhere close to four to six years of cumulative patches, fixes and core OS improvements depending on the target hardware it's being installed on. Much of those improvements are in the kernel and associated core subsystems where memory management, networking and I/O is being touched.
While Obi-Vaughn will argue otherwise, this is no different from the types of improvements one might observe when installing a Linux 3.x-based distribution that is current on 4-year-old and and 6-year old hardware versus a much older version of that same Linux distribution.