Is it possible to upgrade the CPU on a 266MHz PowerMac G3 MiniTower

The "750" is the number given to the G3 PowerPC processor: a PowerPC 750. The processor's speed isn't 750 MHz. Some years ago, when your beige G3 wasn't quite so old, there were third-party, faster G3 and G4 processor upgrades being marketed for those models. Even if you bump the processor speed, the 66 MHz system bus speed won't be increased and you don't have a dedicated AGP graphics bus. All PCI video cards are installed in one of the 33 MHz PCI slots. The lag that you're experiencing is due to a combination of the very-dated hardware architecture of those 1997/1998 computers. You could install a faster ZIF (Zero Insertion Force) processor upgrade card, but I don't think you'll experience the results that you'd be hoping for. If I were going to spend the money on a used processor card for a beige G3 in 2016, it would have to be a G4 and very inexpensive. Any money invested in upgrades for a beige G3 will exceed the computer's current market value. You can read old reviews about these upgrades at the Accelerate Your Mac "G3 Zone."

I happen to have an unopened 600 MHz G3 upgrade for Beiges… somewhere around here!

applefanAidyn wrote:

...but the 266MHz really chokes when playing high performance games...

that is kind of an oxymoron, you can not play high-performance anything on a 266MHz G3. I enjoyed learning about DIY upgrades back when I had my G3 and spent way too much on it, but it was a fun hobby and learning experience and I extended it's useful lifespan well beyond it's planned obsolescene. Back in the day, you could buy from reputable manufacturers who supported their products and had warranties, etc. But even with the historical articles and reviews on XLR8YourMac.Com available as a resource, you really don't have the same level of parts availability and vendor support today, where the costs of as-is, no-returns parts just don't seem worth the risk of experimenting with a working machine and turning it into a non-working machine. I totally understand reasons for keeping an older machine going, just keep in mind the benefits of those upgrades will be very minimal for the expense. I really had fun tracking my Xbench scores after making upgrades to the hard drive, video card, CPU, but the machine would still hang up when trying to run high performance games, the motherboard just can't make all those upgrades work together any faster.

That 266 Mhz PowerMac is really not going to do high end anything!

The added upgrades that you may find ( CPU ZIF cards, PCI video upgrade cards, adding PCI USB/FireWire cards,adding more RAM etc.) won't help much with Internet surfing as Macs that old are hopelessly behind the current web standards AND won't do well with today's Internet.

The highest CPU ZIF upgrade card you could get for that model PowerMac, at that time, was either a 500 MHz CPU card or a 1.0 GHz CPU upgrade card.

I havent seen these around on eBay in quite awhile.

Plus, the highest, usable, OS X version you might be able to install, if you are able to find the OEM install discs, reasonably, cheap might be OS X 10.3 Panther.

Way behind any of the newer PowerPC Macs that are capable of running OS X10.4 Tiger or 10.5 Snow Leopard.

You have to weigh out what you are going to spend on a 20 year old Mac that is worth, basically, bupkiss, to make it do whatvever it is you are trying to accomplish with this Mac.

applefanAidyn wrote:

I stumbled across a 750 MHz G3 processor on eBay, mean't for upgrading a PowerPC Mac with a slower 233MHz or 266MHz G3 processor. ...

Can you post the actual link to this eBay item for sale that you are considering buying? It may have been a "750 G3" CPU meant for upgrading even older generation PowerPC Macs, like the 6100, 7100, etc series that pre-date the G3 models. If you share with us the specific item you are talking about, maybe we can give a little better info. I recall there being 500MHz G3 and 1GHz G3 and G4 upgrades at one time, those may be hard to find now.