I doubt the drive interleave has anything to do with your problem... With the increased drive rotation speeds and large buffers the interleave no longer factors into the equation... At 10K RPM you have a latency of 3mSec, which at U2 SCSI rates equates to 256KB per rotation, and with a minimum of 2 MB cache (on the first Cheetah drives) you should have no problem with the drive going around a couple of times before you empty the cache. Interleave made a difference when the drives were running at 3600 RPM with 128K cache.
Even with an SCA to 50 pin adapter you should be able to achieve good transfer rates (8 bit Ultra SCSI is 20 MB per sec after all). If I had to guess, I would say you were running the drive in narrow (8 bit) single ended mode. Check the jumpers on the drive and make certain the adapter is specified for the type of connection you are attempting. Termination is also a very good possible source of your problems. Most (if not all) single ended drives have the ability to provide termination, while most (if not all) LVD drives do not, although they can provide termination power. Perhaps the "slower" drive you have is an U.W. drive with termination enabled, while the Cheetah is running without termination. It is always best (SE or LVD) to run SCSI with a good discrete terminator. Contrary to popular belief, the "classic" Mac OS (or in my mind the real Mac OS) will generally run with questionable termination (I have at times run without termination on the drive end of the cable), but you will almost certainly have a performance hit as a result.
Without additional information I cannot say much more. Things like a very full and very fragmented drive will cause the transfer rates to plunge (too many full stroke seeks). Oh yes, if the drive is failing, you will also see your transfer rates tank as the drive make multiple attempts to get the data to be verifiable and the bad sectors are mapped out.
Here are some good things to check:
1) Verify the (SCA) adapter specs 2) Verify the drives jumper settings 3) Verify bus termination (including termination power) 4) Test with only the target drive on the SCSI bus 5) Test with an empty drive (a freshly formated drive is best)
Derek
on 2/20/04 3:55 PM, Gregg Eshelman at [EMAIL PROTECTED] scribbled:
Have you tried them with something like a Jackhammer wide SCSI card? I don't know if one of those would be fast enough on NuBus.
Actually, I was testing them out on a PCI PowerMac with a G3 upgrade in it
on both the fast SCSI bus as well as an Adaptec PCI SCSI card. Same crappy
throughput no matter where I stuck it.
Are there any SCSI controllers out there that have an 80 pin connection?
What boxes use SCA drives without the adapters to throttle down to 68 or 50
pin?
Hmmm, I should try that with the 18 gig SCA drive I have on my Radius 81/110, which *should* be able to run at the maximum bandwidth the SCSI bus is capable of, which *should* be fast enough for video capture from the Media 100, but is not.
I understand RE: interleave and all from back when installing larger HDs in
Ses, Mac IIs and other older hardware. What I don't understand is why a 10K
rpm drive ends up with 3Mb/sec throughput when a 4GB slower SCSI HD can get
7Mb/sec off the same bus???
Paul/.
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