Reading NorthStar Horizon hard sector disks on PC

[Allison]

>
>Subject: Reading NorthStar Horizon hard sector disks on PC
>   From: "Andrew Lynch" <lynchaj at yahoo.com>
>   Date: Mon, 30 Jul 2007 23:14:17 -0400
>     To: <cctech at classiccmp.org>
>
>Hi,
>
>Is it possible to read, but not necessarily write, a NorthStar Horizon hard
>sector disk using a standard PC NEC 765 type FDC?
>
>If not, why?  The NorthStar controller uses FM and/or MFM encoding but I do
>not understand the reason why. 

The disks do not have any of the needed marks recorded to sychronize to.
Also the check byte is not a CRC of the type that any FDC uses.  As to FM/MFM
yes thats the same but that only defines what the bits sent by the serial 
stream are represented by on the magnetic media bot the next level up
in the formatting of the data.

To simplify, the NS* controller uses the holes to signify where data is 
rather than laying down a complex series of recorded marks to signal
where the contrller where the disk is at.  The result is that the 
controller hardware is simplified and the CPU can do some of the work.


>Based on what I have read, it appears the NorthStar disks are unreadable on
>the PC without special hardware such as the MatchPoint PC and/or Catweasel
>cards.

Correct.


Allison