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From: bjoern@drdhh.hanse.de (Bjoern Kriews)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: Hard Disk Sector 0 Questions
Message-ID: <2231.03.91@drdhh.hanse.de>
Date: 12 Mar 91 21:40:00 GMT
References: <5208@mcrware.UUCP>
Organization: Digital Island
Lines: 78

From article <5208@mcrware.UUCP>, by ric@mcrware.UUCP (Ric Yeates):
> I need to write some software to add partitions to the partition table
> stored on sector 0 of a hard disk.


>     * the table entries are in the following form:
>           struct part_entry {

					WRONG !!! flag has to be here, bit 7 means bootable

>               char name[3];
>               long start;      /* 32-bit sector number */
>               long length;     /* 32-bit length in sectors */
>               char flag;       /* 1 byte flag where 0x01 means bootable */
>           };
> 1. Is any of the above information inaccurate? Incomplete?

Yes. :-)

More questions answered below.

> 5. How might an application read sector 0?  All the GEMDOS calls I found
>    dealt with files only, not the whole device.

If you detect an AHDI or compatible driver, you can set bit 3 in the
Rwabs() mode-word to read physical sectors, but to be safe you will
have to use direct DMA access. (Ask your Microware devdrvr writers)

In germany, there's a VERY good book, called 'Scheibenkleister', 
published by Maxon. It's about all mass-storage devices on the ST.
I don't think that there is an english version, so you'll have to
search somebody reading ger-mish - it worth the action.

I include the C definitions I use for such tools:
(ICD/Supra Rootsectors only - there are official docs from Atari
describing HDX 3.0 Format, but they are (c), so you have to ask Atari.

Hope that helps, Bjoern

---------

#define	PART_EXIST						1
#define	PART_BOOT							128

/* partition definition */
struct part {
  unsigned char   flag;				/* bit 0: exists bit 7: boot		*/
  unsigned char   id[3];			/* partition name								*/					
  unsigned long   start;			/* start sector									*/
  unsigned long   size;				/* size in sectors							*/
    };

/* rootsector structure */
typedef struct {
  unsigned char   prg[0x150];	/* bootprogram									*/
  unsigned char   version;		/* rootsector version number		*/
  unsigned long   cbhd;       /* Driver magic longword        */
  struct part     extp[8];    /* extended parts SED/ICD/Supra	*/
  unsigned int    hi_cc;			/* cylinders on disk						*/
  unsigned char   hi_dhc;			/* number of heads							*/
  unsigned char   filler;			/* unused												*/
  unsigned int    hi_rwcc;		/* reduced current start				*/
  unsigned int    hi_wpc;			/* write precomp start					*/
  unsigned char   hi_lz;			/* landing zone distance				*/
  unsigned char   hi_rt;			/* steprate											*/
  unsigned char   hi_in;			/* interleave										*/
  unsigned char   hi_spt;			/* sectors per track						*/
  unsigned long   hi_size; 		/* total size in sectors				*/
  struct   part   p[4];       /* atari hdx<3.0 partitions     */
  unsigned long   bsl_start;	/* bad sector list start				*/
  unsigned long   bsl_count;	/* number of sectors in bsl			*/
  unsigned int    checksum;		/* fixup for $1234							*/
    } ROOTBLK;


*
*	bjoern@drdhh.hanse.de / Bjoern Kriews, D-2000 Hamburg 76
*