From: alexis@panix.com (Alexis Rosen)
Newsgroups: comp.unix.aux
Subject: Re: SUMMARY: disktab entry for Quantum LP240S
Date: 21 Jul 92 08:50:39 GMT
Organization: PANIX Public Access Unix, NYC

duffiem@wl.com (Mark Duffield) writes:
>Sorry that it's taken me so long to compile this.  An interesting thing
>happened as I assembled a disktab entry for the Quantum LP240S.  I came up
>with two different ones.  The first entry I assembled with the help of HD 
>Toolkit as described in the FAQ.  I was told that the number of tracks per
>cylinder is actually the number of heads.  Someone (Alexis Rosen I think) told
>me that that drive spins at 4400rpm.

Correct. Except that some utilities may include the head on the servo track.
If the # of heads is odd, that's right. If it's even, subtract one. ...unless
the drive uses embedded-servo. Or some other technology I don't know about.

As for the RPM, it may be 4300 or 4800, but I not if I recall correctly- and
it's definitely not 3600, the default.

>The following is the disktab entry I put together:

>LP240S|Quantum240:\
>    :ty=winchester:nc#1818:ns#87:nt#4:rm#4400:

Well, I'm not sure about nt. I seem to recall that 4 is right. As for the
others, I don't remember. The last time I saw a data sheet was months ago.

>The second entry (and associated text) I received from a friend at Apple.  
>The text of the AppleLine message follows:
>>
>>The Quantum LP240S drive is the same mechanism used for the Apple 230MB drive.
>>The following entries apply to both the Apple 230MB and the Apple 400MB drives.
>>
>># Quantum LP240S, Apple 230MB drive
>>#
>>LP240S|HD230SC:\
>>    :ty=winchester:ns=60:nt=4:nc=1930:

This is much closer to correct. Even though I said I don't remember, simple
math (use the formula I posted in the other article) tells me that your entry
is too large by far. You should still use the rm#4400, though.

>># Seagate ST1480, Apple 400MB drive
>>#
>>ST1480|HD400SC:\
>>    :ty=winchester:ns=54:nt=9:nc=1760:

And this should use rm#4800.

>>I should point out that the entries for the file /etc/disktab can be created
>>from the drive specifications and that we do not have access to all the drives
>>in the market.

This is pretty safe.

>>The customer should be able to request the following information from the
>>vendor in order to create his own entries.
>>
>>            Number of Heads = nt
>>            Number of Sectors/Track = ns
>>            Number of Cylinders/Disk = nc

All correct.

>So, now I have a problem.  First, which one do I use?  And second, why does
>Apple's disktab entry differ from the one that I was able to assemble using HD 
>Toolkit.  Not one parameter is the same (except for ty).

Use theirs. I'd forgotten that they had a disktab entry for the 230. Yours is
definitely wrong.

>What I finally ended up doing (don't shoot me), was to backup up the files that
>I needed and to reinitialize the drive with HDSetup.  Since I had only gotten
>A/UX up and running a week earlier, this was not a major task (only time 
>consuming).  This will not allow the drive to perform as the vendor designed
>it to, but it works.  The story about why I wanted the disktab entry
>in the first place is LONG, so I am going to spare you all the details.  
>Suffice it to say my drive works fine now.  

>I hope that someone can shed some light on why the two entries differ so much.

Your utility is giving you incorrect info.

--
Alexis Rosen   Owner/Sysadmin,
PANIX Public Access Unix & Internet, NYC.
alexis@panix.com
{uupsi,cmcl2}!panix!alexis