Path: utzoo!censor!hugh
From: hugh@censor.UUCP (Hugh D. Gamble)
Newsgroups: comp.sys.amiga
Subject: Re: Tales of Mystery and Imagination (LONG)
Summary: ST296N with Comspec SA2000 ctrler.
Message-ID: <498@censor.UUCP>
Date: 13 Apr 89 16:40:10 GMT
References: <345@nadia.UUCP>
Organization: Bell Canada, Business Development, Toronto
Lines: 47

In article <345@nadia.UUCP>, space@nadia.UUCP (Lars Soltau) writes:
... 
> With trembling hands the lucky A2000 owner runs his very own hd performance
> test.   This  test just opens a big file and reads 512K blocks.  The Rodime
> hd  made  a  quite satisfactory 500KB/s, so the new, bigger drive should be
> faster.
> 
> lAo: What! 179KB/s! There must be something wrong!
...
> which fiery letters state:  "SCSI Format Command:  04 00 00 00 XX 00, where
> XX  is  the desired interleave." After a lowlevel format with interleave 3,
> the Seagate hd makes nearly 400KB/s.
> 
> (Curtain.)
> -- 
> Lars Soltau	UUCP: ...uunet!unido!pfm!nadia!space	BIX: -- no bucks --

The ST296N is an RLL (I think) drive that spins faster than the lower
end Seagates (sorry, the spec's at home).  With a vanilla B2000 and a
Comspec SA2000 SCSI controller (non DMA) the optimal interleave is
5:1.  With an A2620, and a new PROM for the SA2000 that takes advantage
of the '020, empirical evidence from diskperf (the recent version from
FISH 18? [Thanks Fred, and Joanne, of course]) showed that a 4:1 
interleave was optimal.  3:1 gave slightly faster reads, but writes
slowed way down.  With SetCPU FASTROM (it makes a difference [thanks
Dave]) this configuration with 4:1 gives a little over 200kB/s.

Needless to say, this is a little dissapointing.  The upside is that
this performance is rock steady no matter how much hi-rez, interlace,
overscan screen DMA you've got going.

I was assuming that if I put in a 2090A (maybe so I can run AMIX,
but forget I said so because it's irrelevent & I'm talking about
AmigaDOS/WB here) I could get the drive down to 1:1 and expect
performance in the 700kB/s range.  The 400kB/s and 3:1 interleave
mentioned above seem low to me.  Where's the bottleneck?  I'm
assuming (possibly incorrectly) that the performance rating used
by the poster should be in the same ballpark as diskperf.

What is the theoretical (for you head game types) and actual
(for you hackers) max rate for a 2500 with a ST296N?

-- 
Hugh D. Gamble (416) 581-4354 (wk), 267-6159 (hm) (Std. Disclaimers)
hugh@censor, kink!hugh@censor
# It may be true that no man is an island,
# but I make a darn good peninsula.