I'm thinking of upgrading from 10.6.8 Snow Leopard to OS X Yosemite. Does anyone know of any problems associated with this? What are the implications / consequences of installing Yosemite? Does it effect functionality of v10.6.8 software or hardware?

Hello Gunny64 and welcome to the community.

First, of all, based on your statements, if you are having issues with your MacBook Pro now, no system upgrade/update is going to solve your Mac's issues.

In most cases, it makes your Mac's performance issues even worse, no matter what OS X upgrade or update it is.

If your system is running slow, we first need to find and why and solve those issues before any thing else can happen.

It would help us to help you if we could have some more technical info about your iMac.

If you choose, please go ahead and download, install and run Etrecheck.

Etrecheck was developed as a simple Mac diagnostic report tool by a regular Apple Support forum user and technical support contributor named Etresoft.

Etrecheck is a small, unobstrusive app that compiles a static snapshot of your entire Mac hardware system and installed software.

This is a free app that has been honestly created to provided help in diagnosing issues with Macs running both OS X Snow Leopard and later OS X versions.

It is not malware and can be safely downloaded and installed onto your Mac.

http://www.etresoft.com/etrecheck

Copy/paste and post its report here in another reply thread so that we have a complete profile of your Mac's hardware and installed software so we can all help with your Mac performance issues.

Next if you are still using the most up to date version of Apple Safari for OS X 10.6.8 and still having issues with websites, you can install an alternate, dedicated web browser that can be updated regularly without upgrading your operating system.

Do a search for and download and install Mozilla FireFox and try using that as your Web browser of choice for awhile.

What software do you use that you need to upgrade the OS to use a more current version?

We need to deal with your immediate problems, first, before I will/can give you and plan and procedures for upgrading your Mac's OS X system

Upgrading to OS X Yosemite will include a newer version of Safari, so you shouldn't experience too much website incompatibility if you upgrade. If your Mac is running slow on Snow Leopard, it may or may not get worse in OS X Yosemite. You should have at least 4GB of RAM to run Yosemite (the minimum requirement is 2GB) - if you're not sure how much you have, the EtreCheck report Michel mentioned can answer that. OS X Mavericks and later include advanced power- and memory-saving technologies which may compensate for slowness. The only crucial thing you usually have to worry about when upgrading from OS X 10.6.8 to a later version is whether your applications will still work - Power PC applications are not supported in OS X 10.7 and later.

Application Compatibility

Check that your computer is compatible with Mountain Lion/Mavericks/Yosemite.

To check the model number hold down the option/alt key, go to the Apple menu and select System Information.

MacBook Pro (Mid/Late 2007 or newer) model number 3,1 or higher

Your Mac needs:

• OS X v10.6.8 or OS X Lion already installed
• 2 GB or more of memory (More is better - 4 GB minimum seems to be the consensus)
• 8 GB or more of available space

Much of the slow down can be directly attributed to the garbage on your system. You have at least two known adware items, which EtreCheck has noted in red. Genieo and Omnibar. You can use Adware Medic to remove those.

You also have a lot of garbage plugins loaded in Safari. Basically every app Google writes is junk. They are all known to eat up RAM, cause memory leaks, and other instabilities. RealPlayer has been known since it first appeared years ago to be one of the worst written pieces of junk under both Mac and Windows. Get rid of it.

Remove at least these items from your plugins:

o1dbrowserplugin: Version: 5.38.6.0 - SDK 10.8 [Support]

Google Earth Web Plug-in: Version: 7.1 [Support]

RealPlayer Plugin: Version: Unknown

googletalkbrowserplugin: Version: 5.38.6.0 - SDK 10.8 [Support]

If you have Google's Chrome web browser, dump that, too. Use either Safari or Firefox.

Beyond that part of it, be aware that any PowerPC apps you own will not run in Lion or later.

Written by Thomas Reed, a long time poster and the ‘expert’ on malware.

Malware Guide – Adware – 10.6 and under

Genieo Uninstall

Genieo Uninstall (2) see post by Linc Davis

Get rid of Trusteer. It doesn’t work well under Mac OS.

Trusteer Rapport Uninstall

Application Compatibility

Applications Compatibility (2)

Once you get the computer working well, one option is to create a new partition (~30- 50 GB), install the new OS, and ‘test drive’ it. If you like/don’t like it it, you can then remove the partition. Do a backup before you do anything. By doing this, if you don’t like it you won't have to go though the revert process.

You are welcome.

I'm assuming that the removal of Geneio, Omnibar, RealPlayer and the plugins is not a matter of simply Deleting/Move to Trash? Am I right in thinking that they need to be completely 'uninstalled' using either software (AdwareMedic) or by a more involved manual method?

Yes, they need to be completely removed. Dragging them to the trash won't get rid of all their effects.

The startup items are okay as long as you are using 10.6. They will not work if you upgrade to 10.10.

Don't forget to get rid of Trusteer Rapport.

You create a partition using Applications/Utilities/Disk Utility/Partition.

Sorry. I keep forgetting Thomas Reed's tool only runs under Lion or later. You can, if you wish, download his older script removal tool, which will purge Genieo from your system.

http://www.thesafemac.com/art/

If you're uncomforatble downloading something else to fix a problem caused by a downloaded and installed item in first place, he has manual instructions here:

http://www.thesafemac.com/arg-identification/

Apple has their own manual removal instructions here:

Remove unwanted adware that displays pop-up ads and graphics on your Mac - Apple Support

No matter which you try, you should make a backup of the system first. Thomas has noted in the past that manually removing Genieo incorrectly can cause your Mac to become unbootable.

It's crucial during the manual removal of Genieo that you DO NOT empty the trash until you reach the point of the instructions that so to do that. Do not delete items as you go through the steps.

Keep in mind that you don't have to change/upgrade your current system, although you do need to get rid of the adware crud. Nor should you do any upgrading until you have first created a full backup to an external drive using Carbon Copy Cloner or SuperDuper.

The safest way to try out Yosemite is to install it clean on an external HD. Then you can reinstall critical apps a few at a time to see how they work with Yosemite. If you get everything working acceptably, you can consider cloning this system onto your internal drive.

You may find that the UI in Yosemite is in many ways inferior to that of Snow Leopard, both aesthetically and functionally. Many questionable choices were made beginning with Lion.

> The safest way to try out Yosemite is to install it clean on an external HD

If I want to do this, is swap file (virtual memory) on the external drive? That would be slow at times. If so, does anyone know if anyone has tried to boot OSX from an external drive but have /var on the internal drive? Many years ago I edited fstab files, but I would need a refresher course and how does OSX (and each version may differ) do it?

If installing Yosemite on an external HD does put swap on the external, a slightly better (but more difficult and slightly less safe) way is to partition the internal disc and install yosemite on the newly created partition, but you need a lot of free disc space to do that.

Back to the original post, is there a summary of the various recent OSX systems and the pro's and con's of each? So far, I have heard Yosemite can be very slow for some users. When I tried Yosemite it consumed a lot of i/o resources writing to (console) log. I have read several posters saying Snow Leopard is their preferred OS.

One hard fact, if I have my info correct, is that Snow Leopard and earlier can run apps written for the Power-PC (even on the Intel machines); Later versions of OSX don't allow that (w/o using a virtual machine).

The swap file will always be on the same partition you boot to. So if Yosemite is on the external drive, that's where the active swap file will be, too. Each bootable drive/partition will contain its own swap file.

Booting from and using an OS on a USB 2 drive will be slower for everthing. A FireWire 800 drive better than USB 2, and USB 3 quite a bit faster than FW800. eSATA or Thunderbolt external drives will be exactly the same as an internal drive since both are a direct extension of the PCI bus.

From what I've noticed over the years, and through many versions of the Mac OS, those who have the most trouble upgrading are those who install a new OS over an old one. I have always set up each new OS on a separate, erased partition so I don't have such issues. Each OS has never failed to be just as fast as the previous one. The only thing that sticks out are actual OS bugs, which you know are directly attributable to the new OS since it can't be blamed on a bad upgrade.

Yes, PPC hit the end of the road with Snow Leopard. The actual PPC-Intel interpretor was owned by another company. Either Apple let the license to use it lapse, or simply never intended to bring it forward indefinitely. I would tend to believe the latter. As you already know, if you have PPC software can't upgrade to an Intel native version, must use, and have a newer Mac which can't boot into Snow Leopard, then the only option is to run Snow Leopard Server in a VM.