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From: jeremy@perf2.asd.sgi.com (Jeremy Higdon)
Newsgroups: comp.sys.sgi,comp.periphs.scsi
Subject: Re: < Connecting Fujitsu M2266SA to SGI SCSI (SOLVED) >
Message-ID: <106450@sgi.sgi.com>
Date: 28 May 91 19:36:14 GMT
References: <41530@unlisys.in-berlin.de> <41691@unlisys.in-berlin.de> <21924@cbmvax.commodore.com>
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In article <21924@cbmvax.commodore.com>, jesup@cbmvax.commodore.com (Randell Jesup) writes:
> In article <1991May14.151513.1347@utstat.uucp> tg@utstat.uucp (Tom Glinos) writes:
> >Still not satisfied I'm trying to get the very last drop of performance
> >out of the drive. Why won't it run any faster than 900KB? The drive is
> >rate for 2MB/sec in asynch mode. 
> >
> >A call to Fujitsu indicated that 
> >	"in my configuration 1MB/sec was a good number." 
> >
> >The nuance of the phone call was that unless you had some VERY good
> >SCSI equipement your aren't going to get anything near 2MB/sec.
> 
> 	Well, the 33c93a can run an ST1480N and a Q210S at full bore at the
> same time (both running disk performance tests (DiskSpeed 3.1)).  The 1480
> gets between 1.5 and 2.0MB/s and the quantum gets 700-900K/s (at the same
> time!)  That's on an Amiga A3000, 25Mhz '030, WD33c93a SCSI chip, with
> Commodore custom DMA/FIFO chip(s) transferring the data to memory with longword
> DMA cycles.  BTW, those speeds above are through the filesystem, which
> generates direct DMA reads for large aligned transfers when possible.
> 
> 	Their interface to the 33c93 might be inefficient (PIO a byte at a
> time, perhaps).  Perhaps the 33c93 is far slower than the 33c93a.

This disk (2266SA) on a 4D/200 (and up) with PowerChannel (IO3) or 4D/25
or 4D/35 should get 2.1 or 2.2 MB/s through the filesystem.  On a
machine with an IO2 (4D/100 and up without PowerChannel), 900KB is
actually pretty good.  When the IO2 was designed, the fast disks were
on VME (SMD and ESDI), so 900KB/s was considered good enough for SCSI.
The IP4 is actually a little faster.  You would probably get about 1.1MB/s.