Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: AE HD Floppy
Message-ID: <14336@cbmvax.commodore.com>
Date: 10 Sep 90 21:30:57 GMT
References: <3027@mindlink.UUCP> <2915@corpane.UUCP>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 57

In article <2915@corpane.UUCP> sparks@corpane.UUCP (John Sparks) writes:
>a72@mindlink.UUCP (Raman Anand) writes:
>
>>Has anyone tried using Generic 1.44K internal IBM drives with Applied
>>Engineering (AE) high density drivers?

>How does the AE drives work anyway? I remember people asking Dave Haynie if
>the new version (then called 1.4) of AmigaDOS would support 1.44 meg floppies
>and the answer was no, because the chip that handles floppy access could not
>support any larger drives. It was a hardware limitation. So, how is AE getting
>amigaDOS to support high density drives?

Well, lemme rephrase that.  It's not so much that 1.44 meg floppies are
impossible, but that 1.44 meg floppies that work exactly like the IBM 1.44
meg floppies are impossible with the floppy controller in Paula.  The specific
problem is that the data density of those floppies is twice of what Paula can
handle.  So you would need some external hardware.  Like what?  Well, some
possibilities:

	[1] Add an external track buffer and some extra logic.  Your floppy
	    mechanism sucks the raw MFM format from the floppy at full speed,
	    feeds it to Paula at her normal speed.  Paula shouldn't have too
	    much trouble digesting that much data, as long as it's not coming
	    in so fast as to cause indigestion.

	[2] Run the floppy drive at 1/2 the normal speed for high density
	    disks.  This is basically what old Macs did to get angular bit
	    densities on their outer floppy tracks without having to support
	    higher linear bit densities.  Same could work for Amiga style
	    floppies, one would think.

	[3] Bag Paula entirely and add a PC style floppy controller on a PIC.
	    You might kringe at this prospect as a plain add on, but I bet if
	    one of those "yet another" 3rd party SCSI controllers had glomped
	    on this one relatively cheap extra chip, they would be noticable
	    above the competition.

	[4] Bag Paula entirely and use a SCSI based floppy disk drive, like 
	    the kind they hook up to the NeXT.  Only don't charge $1000 for
	    it, and possibly support higher densities as well.

>And can CBM maybe license this technology from them and make it an Amiga
>standard? 

You can pretty much figure out what an Amiga-style high density floppy would
look like, but options [3] and [4] would force a different format, which
could be a problem if Commodore adopts a different format as standard.  Then
again, if you're the only kid on the block with something people want, you
may do well.  

>John Sparks         |D.I.S.K. Public Access Unix System| Multi-User Games, Email


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      Get that coffee outta my face, put a Margarita in its place!