Differences between G3 and G4 processors

Hi,

I am new to Macs (I just bought a 14 inch G3 ibook 900 MHz, 640 MB, 100 GB). I bought it on ebay. When I bought it, I was under the impression that G3 and G4 were just different press releases of computers with the same type of processor. What are the differences between the two? For example, why is it believed that my computer will not be able to run 10.5 but the next oldest ibook, 12 inch G4 800 MHz, is expected to be able to run it?

~Damien

The main difference between the two is the inclusion of the Altivec feature in the G4. Altivec provides increased performance, mainly with graphics. There are other advantages to Altivec, but it is noticed most when dealing with graphics.

A very loose comparison could be made with respect to Pentium processors years ago. The introduction of MMX technology showed a vast improvement with Pentium chips, not unlike the Altivec feature in the Macintosh processors.

The later releases of OS X have all shown marked improvement with certain graphic elements and how things are displayed. If 10.5 follows suit (as it likely will) the G3 simply won't have enough power to function properly and it will probably be cut from support.

Google gave this on the first hit and it looks just about right: How the PowerPC 7400/G4 differs from the PowerPC 750/G3. Altivec helped to make the G4 faster, among other things.


Edited to add:

DOH!!!!! DB beat me to it. Rats and poodles! Foiled again.

So a 800 MHz G4 has more power than a 900 MHz G3...Man that stinks. I didn't see that one coming.

Is there any way to upgrade the processor or would I need to buy another computer if I want to have the new OS?

iBook processors are not upgradable. You would probably have to get a newer computer.
Still, 10.5 Leopard has yet to be released so there is no real, concrete way to tell if it will support G3 or not.