Article View: comp.sys.amiga.tech
Article #10638Re: A2090 SCSI vs Video contention - here we go again!
From: Marco Papa
Date: Mon, 19 Dec 1988 03:51
Date: Mon, 19 Dec 1988 03:51
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2713 bytes
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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Path: arc1-ca.pugleaf.net!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