Path: utzoo!attcan!uunet!cbmvax!andy
From: andy@cbmvax.UUCP (Andy Finkel)
Newsgroups: comp.sys.amiga.tech
Subject: Re: A2090 SCSI vs Video contention - here we go again!
Message-ID: <5496@cbmvax.UUCP>
Date: 13 Dec 88 16:43:22 GMT
References: <2453@antique.UUCP>
Reply-To: andy@cbmvax.UUCP (Andy Finkel)
Organization: Commodore Technology, West Chester, PA
Lines: 46

In article <2453@antique.UUCP> cjp@antique.UUCP (Charles Poirier) writes:
>The old video-contention vs SCSI bugaboo is back, in FFS -- could
>someone knowledgeable about Amiga file systems please take a moment to
>peruse this problem?
>

>= 512 to the Mountlist entry for the FFS partition but this didn't help.

MaxTransfer will limit the amount transfered by the FastFileSystem...
this is not the answer to your problem.

I have a couple suggestions; first, are you running FastMemFirst
before mounting your fast file system partitions ?

This is key; we want to keep the file system's buffers out of
C00000 memory, which has the same access penalties as chip memory.

Second, FastFileSystem transfers directly into a programs buffer.
Normally this works great...less copying around, data ends up exactly
where it is supposed to be, etc.  However, what if the program
has its data area in C00000 memory and you are in a high DMA bandwidth
using situation ?  That's right, slowdown.  In this case, you
are better of setting your Mask value in your mountlist
to exclude C00000 memory.  That way the FFS knows not to
DMA directly into any data area there, but instead use its
buffers, which, if you've run fastmemfirst before 
mounting the ffs partition, will be in fast memory.

So, step 1: make sure FastMemFirst is before the ffs mounts in your 
	    startup-sequence file

    step 2: add a MASK=#007FFFFF

	to the mountlist entries of your fastfilesystem partitions.

		andy

-- 
andy finkel		{uunet|rutgers|amiga}!cbmvax!andy
Commodore-Amiga, Inc.

"Possibly this is a new usage of the word 'compatible' with which
 I was previously unfamiliar"

Any expressed opinions are mine; but feel free to share.
I disclaim all responsibilities, all shapes, all sizes, all colors.