Path: utzoo!utgpu!watmath!clyde!bellcore!rutgers!att!whuts!homxb!antique!cjp
From: cjp@antique.UUCP (Charles Poirier)
Newsgroups: comp.sys.amiga.tech
Subject: A2090 SCSI vs Video contention - here we go again!
Summary: OFS fast, FFS slow
Message-ID: <2453@antique.UUCP>
Date: 8 Dec 88 17:59:57 GMT
Organization: AT&T Bell Labs, Holmdel, NJ
Lines: 44

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 installed FFS on my Quantum Q280 80meg SCSI HD, with a small first
partition as Old File System.  My controller is the A2090, I have 2 Meg
expansion RAM, my startup runs the released 1.3 versions of SetPatch,
FastMemFirst, BindDrivers, and Mount.  My hddisk.device is the most
recent I've heard of (V34.4 I think??).  I tried adding MaxTransfer
= 512 to the Mountlist entry for the FFS partition but this didn't help.

FFS works great (2-4 times speedup) for low-bandwidth screens.  But
high-res 4-plane screens slow down FFS on my system by a factor of 10!
(vs OFS.)  Even if this behavior is specific to certain HD/controller
combinations, it seems that the file systems are partly to blame, as
indicated by the test described below.  This is the same problem I had
before with OFS, using an older version of hddisk.device.  Now the
problem has turned up again in FFS.

Test:  I copy the same iff picture to FFS and OFS.  I open Dpaint II,
high-res Lace.  I load the picture from FFS - takes 40 seconds.  I load
the picture from OFS - takes 4 seconds, even with the DPaint II screen
in front.  Personal opinion --  OFS is doing something right that FFS
is not.  A read speed of 1 or 2Kbyte / sec is obviously unacceptable.

I could drag the screen down to speed things up but this is messy, and
for some programs (those with a full-screen window), impossible.  I
could flip to a lightweight screen, but this is not only messy but
deadly, considering the bug in the screen-flipping code that crashes
Amy if two Lace + one Nolace are in use.  I hope you don't think I'm
being too nitpicky - this really is a problem.

Can someone suggest a solution, short of flinging the A2090 off a tall
building?  What would explain FFS being less forgiving of video DMA
contention than OFS?  I do hope someone can fix this.  Maybe yet
another version of hddisk.device??  A patch to l:FastFileSystem??  FFS
is very nice otherwise, but I can't see living with crippled high-res
permanently.

	Thank you very much, whoever you are.
-- 
	Charles Poirier   (decvax,ucbvax,mcnc,attmail)!vax135!cjp

   "Docking complete...       Docking complete...       Docking complete..."