Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!wuarchive!uunet!sjsca4!poffen
From: poffen@sj.ate.slb.com (Russ Poffenberger)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: EISA Disk Controllers
Message-ID: <1991Feb7.215606.10776@sj.ate.slb.com>
Date: 7 Feb 91 21:56:06 GMT
References: <43779@ut-emx.uucp>
Reply-To: poffen@sj.ate.slb.com (Russ Poffenberger)
Organization: Schlumberger Technologies, San Jose, CA.
Lines: 39

In article <43779@ut-emx.uucp> solomon@chaos.utexas.edu (Thomas Solomon) writes:
>I have seen some information about EISA disk controllers.  Apparently,
>this disk controllers can provide transfer rates that are substantially
>higher than anything that PC's have had before.  Austin Computer Systems
>has an EISA controller for their 486 machine which, they claim, can
>transfer at rates up to 33 MB/sec (the key words there being "up to").
>
>Does anyone know the scoop about these controllers?  Specifically, how
>fast can they write to disk in a _continuous_ mode.  We are interested
>in extremely fast disk transfers for some image processing that we
>will be doing.  Ideally, we would like to be able to handle 8 MB/sec
>transfers.  This would allow us to record video images in real time
>from a digitizer without use of a VCR.  However, if we can get
>4 MB/sec, we may be content with that.
>

This is a very elusive subject. It doesn't matter one bit how fast the
controller is if the disk can't handle it. The tranfser rate to/from the disk
(for large sequential access so no cache is involved) is purely a function
of the disk geometry. It all relates to two things, the number of sectors per
track, and the rotational speed of the disks. Most disks run at 3600 RPM, some
new ones will soon have 5400. Sectors per track range from < 20 to > 80.
Obviously, the drives with the larger number of sectors per track will deliver
better performance. Even then, the fastest interface available only reaches
3MB/sec (IPI-2) for single head per surface drives. 6MB/sec for dual head
drives.

SCSI-2 promises greater performance, but there is little hardware available
for this right now. Even so, these are VERY expensive, a disk and controller
would cost you (If they were available for PC, whcih they probably aren't)
several thousand dollars.

Still, the disk is always the limiting factor, not much you can do about this.
Don't get caught up in market hype, you will be disappointed.

Russ Poffenberger               DOMAIN: poffen@sj.ate.slb.com
Schlumberger Technologies       UUCP:   {uunet,decwrl,amdahl}!sjsca4!poffen
1601 Technology Drive		CIS:	72401,276
San Jose, Ca. 95110             (408)437-5254