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From: bgrubb@dante.nmsu.edu (GRUBB)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: IDE vs SCSI
Date: 16 Apr 1993 14:47:23 GMT
Organization: New Mexico State University, Las Cruces, NM
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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)
ALL this shows is that YOU don't know much about SCSI.

SCSI-1 {with a SCSI-1 controler chip} range is indeed 0-5MB/s
and that is ALL you have right about SCSI
SCSI-1 {With a SCSI-2 controller chip}: 4-6MB/s with 10MB/s burst {8-bit}
 Note the INCREASE in SPEED, the Mac Quadra uses this version of SCSI-1
 so it DOES exist. Some PC use this set up too.
SCSI-2 {8-bit/SCSI-1 mode}:          4-6MB/s with 10MB/s burst
SCSI-2 {16-bit/wide or fast mode}:  8-12MB/s with 20MB/s burst
SCSI-2 {32-bit/wide AND fast}:     15-20MB/s with 40MB/s burst
 
By your OWN data the "Although SCSI is twice as fast as ESDI" is correct
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
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)}

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
SCSI-1 interface and think 'SCSI-1' when it maybe a SCSI-1 interface driven
in the machine by a SCSi-2 controller chip in 8-bit mode {Which is MUCH
FASTER then true SCSI-1 can go}.

Don't slam an article because you don't understand what is going on.
One reference for the Quadra's SCSI-2 controller chip is 
(Digital Review, Oct 21, 1991 v8 n33 p8(1)).
