Re: Cheetah vs. UDMA: Bonnie says UDMA is faster! why?

Mark Lehrer (edge@dux.raex.com)
Wed, 25 Mar 1998 16:07:33 -0500 (EST)

On Wed, 25 Mar 1998, Mark Lehrer wrote:
> ncr53c875-0-<0,0>: SLOW WIDE SCSI 10.0 MB/s (200 ns, offset 15)
^^^^^^^^^
Since you selected a maximum synchronous transfer frequency of 5 MHz, the
maximun transfer speed is indeed limited to 10 MB/s (16 bit times 5 MHz).
To get Ultra-SCSI speeds, you have to select 20 MHz.

Yes, this definitely fixed my problem. Thanks again to everyone who
responded.

FWIW here are the Bonnie results with a 20MHz rate. Incredible
improvement on the seeks and block reads; where before the WD was
slightly faster in most tests (not seeks...):

WD 5400rpm UDMA (33200L):

-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
100 1851 86.6 4155 46.1 1549 43.3 1659 83.8 4262 79.0 56.6 6.1

Seagate Cheetah (10K RPM UW-20):

-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
100 2134 94.7 6018 78.1 3199 70.5 2361 90.8 9999 89.6 140.9 17.2

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