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From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: comp.sys.amiga.tech
Subject: Re: dos_stuff
Keywords: fast,faster,fastest
Message-ID: <126083@sun.Eng.Sun.COM>
Date: 10 Oct 89 17:43:35 GMT
References: <5546@ucdavis.ucdavis.edu>
Sender: news@sun.Eng.Sun.COM
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 45

In article <5546@ucdavis.ucdavis.edu> (Brewski Rogers) writes:
>Hi, I am working on a videogame that needs to load lots of data (~120-150k)
>periodically. (Every time a new map gets loaded.) My question: Is it possible
>to get AmigaDOS to approach the speed of simply using the trackdisk device?

Yes, with some fancy disk optimizing.

>The 120K getting loaded usually consists of about 15 files (~8K each.)
>Would using AddBuffers help much? Are there any other things to try that
>might help?

First, put all of the files in one big file, this will help a bit. Then
layout the file so that the FileHeader block in on some track, and then
all of the data blocks for that file are on that track and the next one
over, then on the third track over, put your final set of blocks and
the FileExtensionBlock, and then the some more data blocks. Basically,
by putting the directory entry on the same track as the data, and the
extension block on the same track as it's data the heads won't seek at
all and you will get essentially full bandwidth. Now the only way to do
this is to format a disk. Use a custom program to lay down the data file,
let AmigaDOS revalidate the disk and then add the rest of your files. 
After laying down this fast access file, do not ever delete/rename/copy
it or your work will be undone. 

Also check for the existence of extra ram that you could copy those files
into. That would speed things up tremendously.

>I assume that writing the files out to a fresh disk in the order I plan
>to read them should put them as close together as possible. Is this true?

Generally this will help but you won't get the max speed out of the system
because A-Dos still bunches the directory entries together (so that the
dir command is faster) and the data blocks, and for your appplication this
is exactly the wrong thing to do.

>I *REALLY* want to keep the game dos-compatible (Easier, hard-drive installable
>etc.) but there is a maximum to how long loading a new map should take...

Copying to the fresh disk will help, custom layouts will help more. 


--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.
"If I were driving a Macintosh, I'd have to stop before I could turn the wheel."