Whats the difference between g3 and g4?


macrumors newbie
Original poster
Jan 2, 2002
i mean could there be that mutch diference? i have just(chrstmas)bought a 600mghz ibook and i hope they dont throw a g4 in there! How mutch difference speed wize will there be? because i really dont want a old chip!


macrumors 6502a
Jun 7, 2001
Well the g4 is the fourth generation processor from Motorola. The g4 has the 128bit Alti-Vec engine in it, which allows more data to be processed at one time. Thus this makes the DVD encoding almost real-time for the Powermacs when it could take days for some g3 processors. The g3's and g4's are apart of the power pc family, which began 94-95ish. Power PC is one of the main hardware differences between Macs and other computers. Another to know is that power pc chips are RISC based while other machines are CISC based. RISC is by nature faster than CISC but currently CISC has more MHZ than RISC sometimes this does allow CISC to catch up to RISC that's why there is the want/need for a 1 GHZ or 1,000 MHZ machine from Apple. The g3's are more adaptable than the g4's because the g3 has had a longer period of existence compared to the g4. Only a year did the g4 come to the portable market while the g3 has been in portables since 97. The g4 generates more heat than a g3 would so this could cause some problems for the iMacs since they have a fan-less design. More applications are being enhanced for the Alti-Vec engine, which will deliver more performance than a g3 could. This is all I could think of to help you understand some of the ideas between the difference of the g4 and g3 processors.


macrumors regular
Dec 20, 2001
At the beginning, Apple said G4 included one more thing... Velocity engine... however, i'm using both most of the day, and , I should be able to distinguish one then another... and actually I'm not. But one thing, maybe during a video rendering, i see the difference... a small one, but it,S already there !

the processors i work on are : G3 400 and a G4 400.
could be more difficult to see it!


macrumors 6502a
Jun 7, 2001
Alti-Vec Velocity engine it's the same thing with a different name.


macrumors 68030
Sep 13, 2001
Portland, OR

The G4 has Altivec which speeds up programs that are designed to use it. Only certain tasks can be speeded up (Photoshop gets a big boost).

The current G4 has a 133mhz system bus (the current g3 has a 100mhz one), which allows it to use faster RAM. The Sahara (the new G3) has a 200mhz system bus, which should be able to use DDR RAM. I don't know what the Apollo has.

G4s support multiprocessing, G3s don't.

Probably a few other differences too, but those are the main ones.