diehlr said:
Looking very seriously at buying a used Powermac G4. Have a few looming questions.
How do the various L2/L3 cache configurations affect real-world performance in common apps such as movie playback, A/V encoding, and overall system responsiveness?
How much does memory bandwidth play a roll in overall system performance? Are most/all Powermac G4s based on 100/133 mhz SDRAM?
Has anyone done an exhaustive benchmark comparison between various flavors of G4 at similar (as close as possible) clockspeeds with varying amounts of memory bandwidth, or across different G4 motherboards? (Yikes vs Sawtooth vs Digital Audio vs Quicksilver).
First up, check out
http://www.lowendmac.com which has a comprehensive listing of the specifications of practically every Macintosh Apple has ever produced. You will be able to find out details like which RAM type, bus speed, cache size etc etc that each of the PowerMacs use.
Another site which you might find useful is
http://www.barefeats.com. These guys do various benchmarks on all sorts of Mac hardware, and you might be able to find the comparison you're after there. Also take a look at
http://www.macspeedzone.com. And come to think of it, the reviews section of
http://www.xlr8yourmac.com contains lots of reports from people who have upgraded their Macs using various G3 and G4 upgrade cards, and they usually post benchmarks of their before and after speed results. You could probably find some complementary benchmark information there which would aid you in your comparisons.
With regards to different memory speed and bus speed, the December 2003 MacWorld has a review of the new 12", 15" and 17" Aluminium PowerBooks. "What the hell has that got to do with PowerMacs?" I hear you say. The review contains a comparison between the 1GHz 12" PowerBook, and the 1GHz 15" PowerBook. Same speed G4, but the 12" PB has a 133MHz front-side bus and DDR266 memory, while the 15" PB has a 167MHz FSB and DDR333 memory...which makes for a good controlled comparison concerning the effect of FSB and DDR RAM speed. The benchmark results from the MacWorld tests are:
SpeedMark 3.2 Overall Score (700MHz G4 eMac = 100, higher is better):
12" PB G4/1GHz: 142
15" PB G4/1GHz: 138
Photoshop 7.0.1 Suite (time elapsed, lower is better):
12" PB G4/1GHz: 0:56s
15" PB G4/1GHz: 0:52s
iMovie 2.1.2 Render (time elapsed, lower is better):
12" PB G4/1GHz: 0:53s
15" PB G4/1GHz: 0:52s
iTunes MP3 encode (time elapsed, lower is better):
12" PB G4/1GHz: 0:45s
15" PB G4/1GHz: 0:43s
Quake III frame rate (higher is better):
12" PB G4/1GHz: 64
15" PB G4/1GHz: 73
Cinema 4D XL 7.303 3D Render (time elapsed, lower is better):
12" PB G4/1GHz: 7:00m
15" PB G4/1GHz: 6:54m
MPEG-2 encode (time elapsed, lower is better):
12" PB G4/1GHz: 14:45m
15" PB G4/1GHz: 13:59m
As you can see, there isn't a whole lot of difference (excepting the 3D benchmarks, but the 15" PB has a faster video chip), except in the MPEG-2 encoding benchmark. Make what you will of these results...obviously the logic board in the 12" and 15" are probably different, they contain different graphics chips, and they may contain different hard drives too. But all in all, they are fairly closely matched, despite their differences in FSB and RAM speed.
If I was looking for a second-hand G4 system, the main thing I'd look for would be an AGP graphics slot. Quartz Extreme can really give GUI performance a nice boost and make the system feel more responsive (especially important for an older Mac). QE isn't supported (officially) on non-AGP Macs.