Organization: Penn State University
From: <DXB132@psuvm.psu.edu>
Subject: Re: IDE vs SCSI
Distribution: world
Lines: 55

In article <1qmgtrINNf2a@dns1.NMSU.Edu>, bgrubb@dante.nmsu.edu (GRUBB) says:

>DXB132@psuvm.psu.edu writes:
>>In article <1qlbrlINN7rk@dns1.NMSU.Edu>, bgrubb@dante.nmsu.edu (GRUBB) says:
>>>In PC Magazine April 27, 1993:29 "Although SCSI is twice as fasst as ESDI,
>>>20% faster than IDE, and support up to 7 devices its acceptance ...has
>>>long been stalled by incompatability problems and installation headaches."

>>I love it when magazine writers make stupid statements like that re:
>>performance. Where do they get those numbers? I'll list the actual
>>performance ranges, which should convince anyone that such a
>>statement is absurd:
>>SCSI-I ranges from 0-5MB/s.
>>SCSI-II ranges from 0-40MB/s.
>>IDE ranges from 0-8.3MB/s.
>>ESDI is always 1.25MB/s (although there are some non-standard versions)

>By your OWN data the "Although SCSI is twice as fast as ESDI" is correct

(How is 0-40 twice 1.25? Do you just pick whatever SCSI setup that makes
the statment "correct"?)
Even if you could make such a statement it would be meaningless unless
you understood that ESDI and IDE (I include SCSI and ATA) are
completely different (ESDI is device-level, like MFM/RLL).


>With a SCSI-2 controller chip SCSI-1 can reach 10MB/s which is indeed
>"20% faster than IDE" {120% of 8.3 is 9.96}. ALL these SCSI facts have been

Great, you can compare two numbers (ATA has several speed modes, by the
way) but what the article said was misleading/wrong.

>posted to this newsgroup in my Mac & IBM info sheet {available by FTP on
>sumex-aim.stanford.edu (36.44.0.6) in the info-mac/report as
>mac-ibm-compare[version #].txt (It should be 173 but 161 may still be there)}

I would recommend people call the NCR board and download the ANSI specs
if they are really interested in this stuff.


>Part of this problem is both Mac and IBM PC are inconsiant about what SCSI
>is which.  Though it is WELL documented that the Quadra has a SCSI-2 chip
>an Apple salesperson said "it uses a fast SCSI-1 chip" {Not at a 6MB/s,
>10MB/s burst it does not. SCSI-1 is 5MB/s maximum synchronous and Quadra
>uses ANsynchronous SCSI which is SLOWER}  It seems that Mac and IBM see

Something is missing there. :) Anyway, I agree. There's a lot of
opportunity for marketing jingo like "SCSI-2 compliant" which tells
you nothing about the performance, whether it has "WIDE" support, etc.

>One reference for the Quadra's SCSI-2 controller chip is
>(Digital Review, Oct 21, 1991 v8 n33 p8(1)).

What does it use? Hopefully a good NCR chip (e.g. 53c710)

