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From: lphillips@lpami.wimsey.bc.ca (Larry Phillips)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Ohhh, just another hack idea.
Message-ID: <2376@van-bc.UUCP>
Date: 20 Apr 89 14:30:25 GMT
Sender: root@van-bc.UUCP
Lines: 48

In <10751@mcdphx.phx.mcd.mot.com>, dbk@teroach.UUCP (Dave Kinzer) writes:
>    Since nobody responded to the deeper FIFO question for a 2090a 
> (although I admit I posted in the no.tech group), I have come up with
> yet another hack project idea.

  I was thinking about answering this one, but lack of definitive information
on the feasibility kept me from doing so. The idea is intriguing, and the next
time I have my 2090A out, I'll see if I can find the FIFO(s), and then see if I
can find a replacement that is deeper, and give it a try. I really don't have a
problem with mine unless I go out of my way to create it by having a fairly
complex picture displayed. If I did have the problem often, I would probably
opt for Khalid Aldoseri's 'Patch2090', that solves the problem quite nicely.
The hardware solution would be preferable of course.

>    If one were to half the RPM rate of a 1.2meg 5.25 inch floppy 
> (or a 1.44meg 3.5 inch floppy), the Amiga floppy disk circuitry could
> still send at 250Kbits/sec and this would be deposited on the drive
> at the appropriate bit density (normal bit rate is 500Kbits/sec).
> This would allow more sectors to be placed per track on the drive.
> The question is, can the trackdisk.device handle reading/buffering/writing
> twice as many blocks per track as normal?  Can this just be specified
> in the MountList?

  There are two possible sources of problems in the above scenario. The first
is that of media, and the second, closely related, is that of the heads. In a
1.44 MByte floppy, the media is definitely different, having a higher
coercivity. In order to compensate for this, the head must put out a higher
write current, and may well have other characteristics that help them to be
able to get high densities.

  You might be able to get away with slowing the rotation to a degree, but I
doubt very much that you could halve the RPM and still get reliable operation.

  The only thing necessary to use a different number of sectors per track from
a system point of view is to create a mountlist entry (with a different name,
ie. DF4:), and specify the specify the different geometry with that.

-larry


--
Frisbeetarianism: The belief that when you die, your soul goes up on
                  the roof and gets stuck.
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|   //   Larry Phillips                                                |
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