Xref: utzoo comp.periphs:1233 comp.unix.wizards:11673
Newsgroups: comp.periphs,comp.unix.wizards
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: query: new disk drive for VAX
Message-ID: <1988Oct12.164433.17763@utzoo.uucp>
Organization: U of Toronto Zoology
References: <4198@bsu-cs.UUCP> <3531@phri.UUCP> <10199@eddie.MIT.EDU> <10209@eddie.MIT.EDU> <20391@sgi.SGI.COM>
Date: Wed, 12 Oct 88 16:44:33 GMT

In article <20391@sgi.SGI.COM> markb@denali writes:
>ESDI will blow the doors off SCSI if done correctly.  ESDI can go to
>24 MHz, which compares nicely with SMDE.  Currently available drives
>are at 15 Mhz. 

Uh, say what?  SCSI transfer rate, at full bore, is 4 MB/s (note, not
Mb/s), which is 32 MHz.  Sounds comparable to me.  Of course, there are
a lot of cruddy SCSI controllers which can't hack that kind of speed,
but then, there are cruddy ESDI and SMDE controllers too.

>ESDI bus times are measured in microseconds, while 
>SCSI can be looked at in milliseconds.

References, please.  I've seen both SCSI and ESDI specs, and somehow I
failed to notice any such disparity.  In the specs, not the current
(often lousy, for both) implementations.

Do remember that this is, to some extent, an apples-and-oranges comparison,
since SMDE and ESDI are drive-to-controller interfaces and SCSI is a
controller-to-host interface.  Since there *has* to be a controller
between a disk drive and a SCSI bus, the quality of the controller makes
a big difference.
-- 
The meek can have the Earth;    |    Henry Spencer at U of Toronto Zoology
the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu