[G4] New system...

[Joseph B. Gurman]

     Vernon LeMoignan wrote:

>A dual 1.25 G4 (according to benchmarks and comparisons I have seen)=20
>will perform about the same as a single 1.8 G5. The dual G4 will be=20
>faster if you are doing a lot of multitasking.  My dual g4 benchmarks=20
>at 162(with a fast hard drive) using x bench, while the dual G5's are=20
>posting numbers around 200, single 1.6 around 140, and single 1.8=20
>around 165.
>
>You can get a lot more memory in a G5, but you only have half the space=20=
>
>for internal expandability of hard drives and optical drives.
>
>The G5's performance might increase, over time, as the OS and=20
>applications are optimized for the new processor and architecture.
>
>I think the dual G4's are a better value as far as bang for the buck.=20
>you'll get mid range G5 performance for mid range imac price.

     I beg to differ.... and I have both machines sitting on my desk at work.

     If you do anything that requires moving substantial amounts of 
data from memory to the CPU (the original poster mentioned DV and 
MPEG2 content and DVD burning, but games, image editing, &c. all 
apply), you will notice an impressive difference. We often create 
1024 x 1024 animations of sequences of images from a spaceborne 
telescope. They run 50% faster on the 1.8 GHz G5 than on the dual 
1.25 MDD G4. (Interestingly, it turns out that for that particular 
application, memory bandwidth is the only determinant of speed: the 
animations run as fast on the 1.8 as the do on a dual 2.0 GHz G5.)

     Who doesn't use lots of memory bandwidth these days? Someone who 
never burns CD-R's or watches DVD's, edits images or video, plays 
graphics-intensive games, downloads QT movies from the Web and plays 
them.... but just uses their machine for text processing, browsing 
very simple Web pages, and e-mail. In other words, people for whom 
the dual G4 was overkill.

     One other area in which the G5's excel: disk bandwidth. Coupled 
with the memory bandwidth, data transfers to/from disk on the serial 
ATA drives are amazing (I was getting 55 MByte/s, sustained, 
yesterday while reading and writing a 1.7 Gbyte animation file under 
10.3.) Yes, you can't put four hard drives in a G5.... but you can 
put in half a Terabyte of disk space on two serial ATA drives. Once 
again, if your demands on a machine are light, neither dual G4 nor G5 
is really needed.

						Joe Gurman
-- 
"I love deadlines. I love the whooshing sound they make as they go by."
                                                             - Douglas 
Adams, 1952 - 2001

Joseph B. Gurman, NASA Goddard Space Flight Center, Solar Physics
Branch, Greenbelt MD 20771 USA