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From: liber@darth.PGH.PA.US (Eric Liber)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Help with Quantumn Q520 Hard disk
Summary: specs
	 '
Keywords: quantumn hard disk 520
Message-ID: <530@darth.PGH.PA.US>
Date: 27 Nov 89 12:56:16 GMT
References: <43367@bu-cs.BU.EDU>
Organization: Darth Software, Pittsburgh Pa.
Lines: 43

In article <43367@bu-cs.BU.EDU>, ngeow@bu-cs.BU.EDU (Yee Ngeow) writes:
>   I recently obtained a Quantumn Hard disk, model 520. Can anyone who
> know the drive parameters let me know what they are? Specifically I need
> to know: (Just fill in the blanks)
> 
 
 Cylinders       : 512
 Heads	         : 4
 Format MFM/RLL	 : MFM
 Reduce write cyl: 256
 Write precomp	 : 256
 Error corr. bits: 11  - This is usually dependant on the controller used
 Step rate	 : I am not sure what you want here - most (all?) modern 
                   controllers will use buffered stepping so the actual rate
                   the drive works at is irrelavant.  However the drive is 
                   specified as being:

                     Track to track : 10ms  (12ms max)
                     average        : 45ms  (49ms max)
                     Full Stroke    : 80ms  (90ms max)
                     average latency: 8.5ms

                     Transfer rate 5.00Mbits / sec

                     Capacity (unformated) 21.33MB
                     
                     Interface: ST506/412

I have used the 40 meg version (Q540) and it is a fine (if a little slow) 
drive.  DEC uses them as the RD52a.  One note of warning :  This drive uses
a tracking techinque known as embedded servo wedge.  As such it reserves a 
small portion of the end of each track for a track positioning signal.  
Therefore, the controller electronics must be smart enough to format the drive
in somewhat less than 360 degrees.  MOST modern controllers (last 4 years?)
can deal with this automatically.  I have run into some that either were not
capable of writing this way or required a specific bit to be set in a control
register that was not automatically done by the low level format process.  I 
only pass this along as a warning since it caught me by the a**.  If you are
using a standard MFM ST506/412 controller of relatively recent manufacture 
then you should have no problems.

Good Luck
Eric (the red baron) Liber