Subject: Re: VAXstation 2000 Progress --- MFM controllers?
To: Allison J Parent <>
From: Michael Kukat <>
List: port-vax
Date: 02/18/2000 07:39:56
Hi !

On Thu, 17 Feb 2000, Allison J Parent wrote:
> <1) I think you have to assume there are 1/2 as many sectors per track.
> no.  That would be dependant on the controller and the sector size.  Often 
> for a fixed sector size the RLL encoded one will have more sectors.

I think we are talking of the classic way to format disks. Today, the inner
tracks have less sectors than the outer tracks, i don't think, this is easy
for the HDC9224. The way i know it from earlier times: MFM uses 17 sectors
and RLL uses 26 sectors. This was fixed, so you can calculate the gain.

> <2) You have to re-low-level format the drive.
> It's a must going either way.  Also only format the drive when it's reached 
> operating temperature.  It does make a difference.

And in the final installation position, the drive should be formatted in
exactly the same situation as it sees the rest of its life in action :-)

> <3) Not all drives will tolerate the change.
> Some are not up to doing reliable RLL.  Interrelated with controller.  
> Also those that don't do rll well often have a poor MFM record or are 
> very old drives.

I never had problems, but the times i did such things are about 10 years away,
there i only has 20-40 MB disks to try with. Maybe they just are uncritical.


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