Getting the most out of my old Mac

I have an old Mac running 10.5.8. It's a Power Mac G5, and I could use it as my primary Mac (for most things), if my Intel Mac mini went down. It has 4GB of RAM; it could go much higher (up to 16GB), but 4GB seems to be more than enough for running Leopard. It has a 128GB SSD as the startup disk, and the other internal drive is a 2TB hard drive. The currently installed video card is stock - nothing special, good enough for my purposes.

It's connected to the HDTV in the living room for its display; it's "hidden" behind the HDTV. It uses my stereo system as its speakers. It acts as my network storage "data dump." I can watch videos on web sites like YouTube (although less of that since getting an Apple TV), as long as the web site uses HTML5-based videos (not Flash-based video). The last version of iTunes for PowerPC Macs (10.6.3) still works with the current iTunes Match service, so I can stream my complete iTunes music library on it. Since it's next to my stereo system, I have done and still do audio recording on it (using an older version of GarageBand). For example, to digitize old music vinyl and tapes. I also use it to record audio from my TV cable box.

I don't know if you have an iMac G4 or G5. If it's a G5, it may benefit noticeably from an SSD startup disk, because it has a SATA interface. For a G4, due to its older PATA interface, an SSD is probably less effective at increasing overall performance. But it would likely improve some things like startup time, and it may benefit an iMac (G4 or G5) by producing less heat and drawing less power, compared to a standard 3.5-inch hard drive (less stress on the aging system). Definitely maximize its RAM. Storage and RAM - You can't really do anything else internally, since it's an iMac.

For software, use TenFourFox as its web browser. Safari for 10.5.8 is old and has not be updated in years. TenFourFox is a special build of FireFox, actively maintained by a dedicated developer, optimized for PowerPC Macs running Tiger or Leopard.

http://www.floodgap.com/software/tenfourfox/

TenFourFox is what makes my PowerMac G5 still useable as an "every day" computer, more than any of its hardware upgrades.

Your question is kind of like asking "I have a old car with a gasoline engine. What is the best performance I can get from it via upgrades, etc.?"

Without details of your iMac it is pretty much impossible to suggest anything other than generalities.

What model iMac do you have and how much RAM is installed?

You can get the model identifier with the System Information app by holding down the Option key and going to the  menu:

Or you can download and run Etrecheck. Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here (and recommended by Apple Support personnel) in the ASC to provide a snapshot of the system. That will tell us most everything we'll need.

Realize that even if you upgrade the operating system to the maximum possible on that computer it will still be 4 major versions behind the current version. Now there's still a fair number of people who are content to nurse an older machine along and don't mind being behind the times a bit, but that is really user dependent. If you do not have this kind of patience and interest in getting old things to work (do you own a collector car?) then you are better off skipping upgrades to this machine and look into getting a newer model. One thing I can see from the specifications you provide is it could do with more RAM but I am not familiar with iMac models and I believe on some models it is a complicated procedure. Another option would be to install Snow Leopard operating system which you can get from Apple for $20. However, many software developers are dropping support for Snow Leopard so it isn't much of a step forward.

That's an Intel-based iMac, and not that old or out-dated. If it came with 2GB of RAM, it's probably this one

http://www.everymac.com/systems/apple/imac/specs/imac-core-2-duo-2.66-20-inch-al uminum-early-2009-specs.html

You can actually run the latest version of OS X, and related software like Mail, iTunes, and Safari web browser. However, to upgrade it passed 10.5.8, you need to upgrade it to Snow Leopard (10.6). You can do so by ordering the Snow Leopard installation disc, which Apple still sells for $20

http://www.apple.com/shop/product/MC573Z/A/mac-os-x-106-snow-leopard

Once Snow Leopard is installed, you can run the Mac App Store, and upgrade it further. The most useful hardware upgrade is to increase its RAM to at least 4GB, or to the maximum of 8GB (not that expensive these days), by replacing your current pair of RAM modules. Here's a list of options from OWC

https://eshop.macsales.com/MyOWC/Upgrades.cfm?sort=pop&model=563&type=Memory

Here's information about upgrading OS X to the latest El Capitan (10.11)

https://www.apple.com/osx/how-to-upgrade/

You can run El Capitan with your current RAM, but it should run noticeably better with at least 4GB of RAM (8GB is even better). You can upgrade the OS X first, see how it runs, and then upgrade the RAM later.

NOTE: Some of your third-party software may not be compatible with later versions of OS X.

I would seriously advise that you install the maximum RAM your year and model iMac can take, which is 8 GBs of RAM.

If you decide to upgrade to later versions of OS X, you will need this extra RAM for sure

Correct and reliable Mac RAM can ONLY be purchased from online Mac RAM sources Crucial memory (crucial.com) or OWC (macsales.com).

https://eshop.macsales.com/item/Other%20World%20Computing/8566DDR3S8GP/

RAM is user upgradeable and, relatively, easy to install.

https://eshop.macsales.com/installvideos/imac_mid_2007_mem/

Good Luck!

Before embarking on a major OS upgrade, it would be wise, advisable and very prudent if you have a good,working backup of your current system to an external connected and Mac formatted Flash drive OR externally connected USB, Thunderbolt or FireWire 800, Mac formatted hard drive. Then, use either OS X Time Machine app to backup your entire system to the external drive OR purchase, install and use a data cloning app, like CarbonCopyCloner or SuperDuper, to make an exact and bootable copy (clone) of your entire Mac's internal hard drive. This step is really needed in case something goes wrong with the install of the new OS or you simply do not like the new OS, you have a very easy way/procedure to return your Mac to its former working state.
Then, determine if your Mac meets ALL minimum system install requirements.
Mac OS X v10.6 Snow Leopard system requirements
Purchased Installer disc here.
http://store.apple.com/us/product/MC573Z/A/mac-os-x-106-snow-leopard
To install Snow Leopard for the first time, you must have a Mac with:
An Intel processor
An internal or external DVD drive, or DVD or CD Sharing
At least 1 GB of RAM (additional RAM is recommended)
A built-in display or a display connected to an Apple-supplied video card supported by your computer
At least 5 GB of disk space available, or 7 GB of disk space if you install the developer tools.
Then use the OS X Software Update feature of OS X 19.6.3, located in the System Preferences Panel to update your iMac to OS X 10.6.8 and to updated all other installed Apple software and security updates.

OS X Combo Update here.

Mac OS X 10.6.8 Update Combo v1.1

To install OS X 10.8 Mountain Lion OR go straight to installing the free OS X 10.10.11 El Capitán, you need one of these Macs:
OS X 10.8 Mountain Lion purchased emailed download code here.
http://store.apple.com/us/product/D6377Z/A/os-x-mountain-lion
Apple will send you an email for the special download code for the Mac App Store within three days of purchasing the download code.
iMac (Mid-2007 or later)
MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later)
MacBook Pro (13-inch, Mid-2009 or later),
MacBook Pro (15-inch or 17-inch, Mid/Late 2007 or later)
MacBook Air (Late 2008 or later)
Mac mini (Early 2009 or later)
Mac Pro (Early 2008 or later)
Xserve (Early 2009)
Your Mac also needs:
OS X Mountain Lion, Lion, or Snow Leopard v10.6.8 already installed
2 GB or more of memory (I strongly advise, at least, 4 GBs of RAM or more)
8 GB or more of available space
Next,
If you run any older Mac software from the earlier PowerPC Macs, then none of this software will work with the newer OS X versions (10.7 and onward). OS X Snow Leopard had a magical and invisible PowerPC emulation application, called Rosetta, that worked seamlessly in the background that still allowed older PowerPC coded software to still operate in a Intel CPU Mac.
The use of Rosetta ended with OS X Snow Leopard as the Rosetta application was licensed to Apple, from a software company called Transitive, which got bought out, I believe, by IBM and Appe could no longer secure their rights to continue to use Rosetta in later versions of OS X.
So, you would need to check to see if you have software on your Mac that maybe older than, say, 2006 or older.
Also, check for app compatibilty here.
http://roaringapps.com/
If you have any commercial antivirus installed and/or hard drive cleaning apps installed on your Mac, like MacKeeper, CleanMyMac, TuneUpMyMac, MacCleanse, etc. now would be a good time to completely uninstall these apps by doing a Google search to learn how to properly uninstall these types of apps.
These types of apps will only cause your Mac issues later after the install of the new OS X version and you will have to completely uninstall these types of apps later.
Once you have determined all of this, you should be able to find the latest versions of OS X by clicking on the Mac App Store icon in the OS X Dock and then login to the Mac App Store using your Apple ID and password and if you purchased a download code, input that code.

If you chose the free download of OS X 10.11 El Capitán,
You can then begin the download and installation process of installing the newer versions of OS X from the Mac App Store.
Good Luck!

Awesome Job, so far!

Great news to learn!

Continued success on the your updates/upgrades on your Mac.

It should give you another few years on performance and enjoyment!

Checked the system - now showing 8Gb Ram and 10.6.3 Operating System

Be sure to run Software Update (from the Apple menu). The last version of Snow Leopard is 10.6.8, and there were probably some "Security Updates" too. So, after doing one Software Update, select Software Update again to catch any other updates that are dependent on installing a previous update.

Opera is pretty good, for use with Snow Leopard. 🙂 The current version of FireFox

https://www.mozilla.org/en-US/firefox/new/

also still supports Snow Leopard, according to this

https://www.mozilla.org/en-US/firefox/46.0.1/system-requirements/

For the printer, if you plan on staying with Snow Leopard for a while, check the manufacturer's web site to confirm there's a version of the printer driver that works with 10.6.8. If it's a recent model, there may not a driver for it that works all the way back to 10.6.8. If you plan to upgrade to El Capitan, there should be a compatible printer driver. Just do a quick check of the printer's technical specs to confirm it is compatible with OS X.