Path: utzoo!utgpu!attcan!uunet!husc6!bloom-beacon!oberon!pollux.usc.edu!papa
From: papa@pollux.usc.edu (Marco Papa)
Newsgroups: comp.sys.amiga.tech
Subject: Re: A2090 SCSI vs Video contention - here we go again!
Message-ID: <14146@oberon.USC.EDU>
Date: 19 Dec 88 03:51:45 GMT
References: <2453@antique.UUCP| <5496@cbmvax.UUCP>
Sender: news@oberon.USC.EDU
Reply-To: papa@pollux.usc.edu (Marco Papa)
Organization: Felsina Software, Los Angeles, CA
Lines: 47

In article <5496@cbmvax.UUCP| andy@cbmvax.UUCP (Andy Finkel) writes:
|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?
|I have a couple suggestions; first, are you running FastMemFirst
                                                     ^^^^^^^^^^^^
|before mounting your fast file system partitions ?

My question is as follows:  what if you've one of the "autoboot" devices
like the GVP board or the A2090A? With the GVP one can have a single
partition, ALL of it FFS and still boot from it.  So the FFS is up 
even before FastMemFirst can ever be run.

|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.

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

Can't do this when "autobooting" an FFS partition. [or is there another
way to di it?]

|
|    step 2: add a MASK=#007FFFFF
|
|	to the mountlist entries of your fastfilesystem partitions.

I guess in my case, I can only do Step 2. Is that enough to avoid all the
problems?

-- Marco Papa 'Doc'
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