Optimal physical configuration of hard drives

Question

Hello,
I have just purchased a new hard drive and would input on the optimal bay to install into. My machine has two rear ATA/100 bays and two forward ATA/66 bays. My hard drives are as follows:
- IBM Deskstar 60GXP 60GB 7200 ATA/100, 2MB(?) cache (Apple original boot drive)
- Maxtor DiamondMax Plus 9 250GB 7200 ATA/133, 8MB cache
- Seagate Barracuda ST3250623A 250GB 7200 ATA/100, 16MB cache
I still boot from the Deskstar. I'd like to dedicate a drive toward highest performance for video. A few specific questions:
1. Would the Barracuda be the fastest drive among these on my existing system since it has the most cache, or would the ATA/133 drive somehow be faster even though it has half the cache and the bus is only ATA/100?
2. Generally speaking, DDR memory can be run ok on a bus slower than the memory is rated for, the memory just runs at the slower bus speed; is it the same for hard drives (specifically, running an ATA/133 drive on a slower bus)?
3. Is it better/faster to run an ATA/133 drive on the ATA/66 bus or the ATA/100 bus?
4. Is there any "overhead" when running an ATA/133 drive on a slower bus (would a native ATA/100 drive be faster than an ATA/133 drive on an ATA/100 bus, all else being equal)?
Thanks!
Power Mac G4 dual 867 Mirrored Drive Doors   Mac OS X (10.4.6)  

Answer 1

High performance, 100 or 133, ATA drives are backward compatible. They will run at the speed of the bus to which they are attached.
The real-world performance of your drives depends on the bus speed, the seek speed, the cache size and efficiency, what else is on the bus, how the drive is configured, and other factors specific to the individual setup. I'd suggest you purchase a copy of Speed Tools and run the drive bench tests to determine your best read/write scores.
Off the top of my head I'd say that your IBM is your slowest drive and your Seagate is your fastest. The fastest single drive setup would be to hook up the Seagate to the ATA100 bus and the other two drives to the ATA66 bus. Of course your Maxtor drive will really take a performance hit in that setup.
If I was doing it, I'd compromise a little on the Seagate's performance and hook up both the Seagate and Maxtor to the ATA100 bus, both set to CS. The IBM won't be much slower than it already is going from ATA100 to ATA66, maybe 2/3 MBs/sec at most. Others may disagree that this is the best compromise.
Carl B.