Path: utzoo!attcan!uunet!cs.utexas.edu!sun-barr!ames!ames.arc.nasa.gov!lamaster
From: lamaster@ames.arc.nasa.gov (Hugh LaMaster)
Newsgroups: comp.arch
Subject: Re: DMA on RISC-based systems
Message-ID: <26636@ames.arc.nasa.gov>
Date: 8 Jun 89 16:18:47 GMT
References: <46500067@uxe.cso.uiuc.edu> <181@dg.dg.com> <185@dg.dg.com> <8479@june.cs.washington.edu> <1213@ttds.UUCP>
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In article <1213@ttds.UUCP> jonasn@ttds.UUCP (Jonas Nygren) writes:
>In article <8479@june.cs.washington.edu> rik@june.cs.washington.edu (Rik Littlefield) writes:
>>In article <185@dg.dg.com>, rec@dg.dg.com (Robert Cousins) writes:
>>< Given that a disk channel will be averaging 200K bytes/second ...

>I have performed a small test on a DECstation3100 with a RZ55-230 Mb disk.

>Write 15x2 Mb: 113 s, 265 kb/s
>Read 15x2 Mb:  117 s, 256 kb/s
>Read 15x2 + write 15x2 Mb (new and in parallell): 281 s, 213 kb/s
>Mean value: 234 kb/s

I have performed some single user tests.  200KBytes/sec reading rate 
is typical for small workstations with SCSI or similar disks, etc.   
With SMD on one of the newer controllers you can do ~600 KBytes/sec.  On
mainframes, I have seen single applications which *averaged* 3 MB/sec on
4.5 MB/sec channels on 8 simultaneous data streams.

So, the ratios quoted seem reasonable to me.

  Hugh LaMaster, m/s 233-9,  UUCP ames!lamaster
  NASA Ames Research Center  ARPA lamaster@ames.arc.nasa.gov
  Moffett Field, CA 94035     
  Phone:  (415)694-6117