Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!purdue!decwrl!mejac!gryphon!jdow
From: jdow@gryphon.COM (J. Dow)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 2090A speed
Summary: Interleave only changes for hard formats
Message-ID: <9472@gryphon.COM>
Date: 10 Dec 88 07:24:05 GMT
References: <14015@cisunx.UUCP> <1135@esunix.UUCP>
Reply-To: jdow@gryphon.COM (J. Dow)
Organization: Wizardess Designs, Hermosa Beach, Ca.
Lines: 57

In article <1135@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes:
>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!
>

I can think of two possible reasons for this lack of whelming performance
changes while diddling interleave. Note that the "mountlist" interleave
will make no difference on FFS disks. To effect a change you must hard format
the drive. A soft format will do zippo.

The other possible reason is continued use of OLDFS. It will show little
improvement with interleave changes and may actually slow down as you
get to smaller interleaves. This is because it makes only 512 byte calls
to the device driver. (FFS is smart enough to make BIG reads where appropriate.)

WIth the HardFrame (should be same with 2090(a)) there is a very dramatic
performance change going frlom 2:1 to 1:1 on a SCSI drive. (ST277N, Mini 8245S,
or Adaptec controllers on ST506 disks. I;ve tried 'em all.)

-- 
Sometimes a bird in the hand leaves a sticky deposit.
Perhaps it were best it remain there in the bush with the other one.

{@_@}
	jdow@bix (where else?)		Sometimes the dragon wins. Sometimes
	jdow@gryphon.CTS.COM		the knight. Does the fair maiden ever
	{backbone}!gryphon!jdow		win? Surely both the knight and dragon
					stink. Maybe the maiden should suicide?
					Better yet - she should get an Amiga and
					quit playing with dragons and knights.