Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!helios.ee.lbl.gov!lll-tis!oodis01!uplherc!esunix!blgardne
From: blgardne@esunix.UUCP (Blaine Gardner)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 2090A speed
Message-ID: <1135@esunix.UUCP>
Date: 5 Dec 88 03:33:42 GMT
References: <14015@cisunx.UUCP>
Organization: Evans & Sutherland Computer Corporation
Lines: 48

From article <14015@cisunx.UUCP>, by ejkst@cisunx.UUCP (Eric J. Kennedy):
> In article <1106@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes:
>>This seems awfully slow for a DMA controller, especially since a
>>couple of friends with the old, non-DMA, CLtd SCSI controller are
>>getting 300K to 350K. One has an ST506 (really, a 5M ST506) with a SCSI-
>          ^^^^^^^^^^^^
>>ST506 adapter, and the other has a 65M Seagate SCSI (I don't know the
> 
> Hey, I've got an old, non-DMA, CLtd SCSI controller, with an ST506-type
> drive and SCSI-ST506 adapter, and I can get 70K on a good day!  That's
> *with* the fast file system!  (30-40K with the old file system.) I
> didn't think speeds in the 300K range were possible.  What can I do to
> speed it up?  This is a stock CLtd. 33Meg drive system for the A1000.

Here's what I remember from talking with my friends: They are using
CLtd's SCSI-DOS 3.0 (a fairly new upgrade, and freely distributable to
CLtd owners as I recall), and an interleave of 2:1 (that's a mountlist
entry of Interleave = 1).

Since I crashed my hard drive a couple of days ago, I took the
opportunity (!) to play with interleave. The results were underwhelming.
I preped the drive and formatted a 10 cylinder (~700K) FFS partition. I
did this with interleave values of 0, 1 and 2. There was no practical
difference between any of the interleaves. An interleave of 0 gave max
read speeds of 180K to 230K, interleave = 1 produced 200K to 230K, and
interleave = 2 yielded 218K and 238K.

From this I have to conclude that interleave on the A2090A has virtually
no effect on performance. Surprising!

The high speeds my friends are getting with the Cltd interface make my
nasty, suspicious mind wonder if CLtd might be distributing a (shall we
say) "optimized" version of diskperf.

Despite the disappointing performance of the ST506 interface on the
A2090A, it does seem pretty immune to overscan. I haven't tried diskperf
with a HAM picture yet, but switching between my usual 704x470 Workbench
screen and the stock 640x200 made no real difference in the speeds. 


(PS If any hints on speeding up the A2090A and this ST4096 were posted
around Thanksgiving, I'd appreciate an e-mail copy. My system lost all
news that should have come in during the 4 day weekend.)
-- 
Blaine Gardner @ Evans & Sutherland    580 Arapeen Drive, SLC, Utah 84108
Here: utah-cs!esunix!blgardne   {ucbvax,allegra,decvax}!decwrl!esunix!blgardne
There: uunet!iconsys!caeco!pedro!worsel!blaine (under construction)
"Nobody will ever need more than 64K."    "Nobody needs multitasking on a PC."