einhorn@triton.unm.edu (E Drew Einhorn ADV.SCI.Inc) (11/06/90)
Over the weekend I spent time running SCSI Evaluator 1.03 on a
Microtech N40S 40 Mbyte external drive in a variety of configurations.
I learned a lot. Somethings still puzzle me.
Turned out the drive inside the N40S is a Sony SRD2040Z with a 28ms
access time. I was expecting a 19ms Quantum drive. My local dealer
says he will get me the 19ms Quantum.
I only measured Read data transfer rates. Following table shows
average data transfer rates in Kbit/sec.
Direct SCSI
Device -------------
Mac Interleave Driver Normal Blind
----- ---------- ------ ------ ------
IIci 1 5676 472 5626
IIci 2 3319 3331 3380
IIci 3 2329 * *
SE 1 460 * *
SE 2 3246 439 3322
SE 3 2296 * *
Plus 1 * * *
Plus 2 440 449 435
Plus 3 739 * *
* I got tired and skipped these tests, wonder if anything else
interesting happens here.
What is the difference between normal and blind SCSI calls. It appears
that when timing is critical normal calls cause us to miss the sector
when it comes around and we have to catch it on the next revolution.
Catching it on the next rev seems to result in transfer rates around
440 Kbit/sec.
Don't have the foggiest idea what how to explain with the 739 Kbit/sec
on the Plus with Interleave 3!
What would the be the effect of putting Marathon 030 accelerators in
the Plus and SE? Should be getting one to try in a SE next week.
Hoping to see something like the 5676 with an interleave of 1.
In addition to big improvements in the access time the 40 Mbyte 19ms
Quantum drive should have faster data transfer rates. Where will the
accelerate SE top out on the SCSI bus. Is there a potential gocha
here?
SCSI Evaluator seems to be stubborn about only doing tests using the
device driver if it was launched from that drive. I was worried that
write tests would trash the MacOS partition I needed to launch from.
It was time consuming installing enough stuff on the disk every time I
reformated with a different interleave, I didn't want to have to do it
everytime I did a write test.
Some related questions.
When running SCSI Evaluator on my Micronet 102 Mbyte internal in my
IIci I get an average read data transfer rate of 10.4 Mbit/sec. With
low (< 20 Kbyte blocks), the standard deviation is very high. Some of
the numbers seem completely out to lunch, I suspect over/under flow
problems with the math. Even when I look at some of the larger block
sizes that miss the apparent arithmetic problems some of the numbers
exceed what I was expecting as the limits on the Mac SCSI bus. What is
the upper limit for SCSI on a IIci?
What are the differences between SCSI and SCSI-2? Are there really any
SCSI-2 drives available yet?
--
einhorn@triton.unm.edu