Subject: RD53 on RQDX3
To: Dave Clarke x8048 <>
From: Bertram Barth <>
List: port-vax
Date: 03/18/1996 16:25:57
Dave Clarke writes:
> Hi,
> 	I was wondering wether the entry for the RD53 on disktab refers 
> to this drive being driven from an RQDX2 ?
> Reason:- RQDX3 says it formats the RD53 17 sectors/track,512 bytes/sector,
> 1024 clinders,8 heads,Interleave 1:1. RQDX2 is similar but 18 sectors/track,
> Interleave 3:1
> So the question is why the difference in the disktab entry 18 sectors/track,
> 963 clinders ?

I'm still not sure what's the real reason behind this, but to me it
looks like this:
- on controllers accessing the drive directly via a triple sect/track/cyl
  (eg. the MFM-controller in VS2000) you have to give/specify the "real"
  physical geometry of the drive to the disklabel
- on controllers hiding the geometry of the drive and accepting LBNs
  (eg. RQDX3) it's easier to find a "logical" geometry which uses all
  the available LBNs, even if this doesn't match the "physical" geometry.