On Nov 2, 2005, at 9:29 PM, NPfield at aol.com wrote: > Lee, I'm using an iMac G4 (w flat panel display); the internal > drive is the one that came with the Mac and the external drive is a > Seagate 300GB Dual-Interface (no model number, apparently).
This is one of those things I played with, out of curiosity, a while back. I wrote a program to do nothing but read bytes off a disk and throw them away. Then I timed it on a large file. (I never did get around to writing a program to time writing.) Here's what I found out. The iMac G4 models used two different Ultra ATA interfaces. They began with Ultra ATA/66, which has a maximum transfer rate of 66 MB/ s. Later models moved to the Ultra ATA/100 which has a maximum transfer rate of 100 MB/s. We can only dream of getting near the maximum data rate. I have a tower G4 with Ultra ATA/100, and my unscientific tests with large files never give over 38 MB/s. (This is with a Maxtor 200 GB 7200 RPM drive.) I assume your dual drive is Firewire and USB2. If you want speed, stay away from USB2 because USB was designed to be a cheap serial interface for things like mice, keyboards and still cameras. Since it's cheap and ubiquitous on PCs, people began using it for hard drives. Firewire was intended from the beginning to be a fast transfer method for things like hard drives and video. It has a smart controller that takes a lot of load off the processor, so the machine can continue doing other things while large copies are taking place. (This is less true of ATA and not true at all for USB.) There are two flavors of Firewire out there, Firewire 1, which can transfer up to 400 Mb/s and Firewire 2, which maxes out at 800 Mb/s. (Notice the small "b" for bit rather than byte.) I suspect your iMac has Firewire 1. I have a 200 GB Western Digital 7200 RPM drive in an external Firewire 2 compatible box. On the G4 tower at home, which has Firewire 1, it maxes out at 35-40 MB/s. In my office, I have a dual G5 Firewire 2, and the same drive transfers as much as 45 MB/s. I suspect the limitation is the drive. I've played with timing the SATA in the dual G5 in my office, and it's speed seems somewhere between 50 and 55 MB/s, but I've not taken the time to do it properly because I just got the machine a month or so ago. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.math.louisville.edu/pipermail/macgroup/attachments/20051103/7d590f3c/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 2398 bytes Desc: not available Url : http://www.math.louisville.edu/pipermail/macgroup/attachments/20051103/7d590f3c/attachment.bin
