Does ESIX still not support RLL?
Kent Karrer
kentkar at shambala.uucp
Fri Apr 26 00:40:10 AEST 1991
In article <3087 at cirrusl.UUCP> Rahul Dhesi <dhesi at cirrus.COM> writes:
>
>I wrote:
>
> How can ESIX even know whether the controller uses RLL? How can
> anybody find this out without ripping the disk apart and analyzing
> the bit-patterns stored on the platter?
>
>Bill Pechter writes:
>
> If there's more than the standard number of MFM sectors per track
> -- you lose. RLL does 25, ERLL (Perstor) does 31... So if the
> driver expects 1-17 only... you may not see your full disk sizes
> (at best).
>
>Which sort of answers the question, but not really. There is no such
>thing as "the standard number of MFM sectors per track." Perhaps there
>is such a thing as "many disk drives use 17 sectors per track, and many
>more don't."
>
>The following is directed not towards Bill, but towards many Usenet
>users who assume that RLL is some sort of disk interface standard.
>It's not! It's just a way of putting bit patterns on the disk
>surface. And it wasn't invented by Adaptec either. RLL means "run
>length limited" -- a way of recording bits such that you never have
>more than m consecutive raw ones or n consecutive raw zeroes. Tape
>drives have used it for years (but they call it GCR or group code
>recording). In the microcomputer world, the Apple II used it on floppy
>
>I still don't see how ESIX (or any other operating system) can find out
>whether the the controller uses RLL. I can see that an operating
>system might not support a certain number of sectors per track, but
>that has only a very nebulous relationship to the recording format
>used, other than that formats denser than MFM yield more sectors per
>track.
>
>Perhaps Usenet posters ought to be saying "ESIX requires no more than
>17 sectors per track" (if that is true, which it probably is not,
>because the disk off which I run ESIX has more than 17 sectors per
>track) instead of blaming it on the recording format.
>
>Better, still, say something like "ESIX doesn't support my disk
>controller, and it happens to use RLL recording, but the recording
>format many or many not have something to do with it."
>--
Well, maybe. But about 18 months ago, I asked the people at ESIX to send
me some product brochures. Within the body of their brocures they specifically
mentioned that they DO NOT support RLL disk controllers. I also have
product brochures from other vendors of unix. They specifcally point out
that they do support RLL. Perhaps it is technically incorrect to refer to
RLL as a standard of some type however, experience with software seems to
indicate to me that someone somewhere within the microcomputer community
has accepted it as a "defacto" standard and therefore I must give it serious
consideration when choosing what software I purchase.
--
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