Re: C/H/S from user space

[Jeff V. Merkey]

Dick,

The model Netware uses for large drives for calculating C/H/S addressed 
this problem years ago and
provides more useful output, since C/H/S is converted into a hieristic 
which acts almost like an MD5 hash
and for a given dimension, does provide unique output for even very 
large drives.

Code Attached.

Jeff



ULONG SetPartitionTableGeometry(BYTE *hd, BYTE *sec, BYTE *cyl,
               ULONG LBA, ULONG TracksPerCylinder,
               ULONG SectorsPerTrack)
{
   ULONG offset, cylinders, head, sector;

   if (!cyl || !hd || !sec)
      return -1;

   cylinders = (LBA / (TracksPerCylinder * SectorsPerTrack));
   offset = LBA % (TracksPerCylinder * SectorsPerTrack);
   head = (WORD)(offset / SectorsPerTrack);
   sector = (WORD)(offset % SectorsPerTrack) + 1;

   if (cylinders < 1023)
   {
      *sec = (BYTE)sector;
      *hd = (BYTE)head;
      *cyl = (BYTE)(cylinders & 0xff);
      *sec |= (BYTE)((cylinders >> 2) & 0xC0);
   }
   else
   {
   *sec = (BYTE)(SectorsPerTrack | 0xC0);
   *hd = (BYTE)(TracksPerCylinder - 1);
   *cyl = (BYTE)0xFE;
   }

   return 0;
}

ULONG SetPartitionTableValues(struct PartitionTableEntry *Part,
                 ULONG Type,
                 ULONG StartingLBA,
                 ULONG EndingLBA,
                 ULONG Flag,
                 ULONG TracksPerCylinder,
                 ULONG SectorsPerTrack)
{

   Part->SysFlag = (BYTE) Type;
   Part->fBootable = (BYTE) Flag;
   Part->StartLBA = StartingLBA;
   Part->nSectorsTotal = (EndingLBA - StartingLBA) + 1;

   SetPartitionTableGeometry(&Part->HeadStart, &Part->SecStart, 
&Part->CylStart,
                 StartingLBA, TracksPerCylinder, SectorsPerTrack);

   SetPartitionTableGeometry(&Part->HeadEnd, &Part->SecEnd, &Part->CylEnd,
                 EndingLBA, TracksPerCylinder, SectorsPerTrack);

   return 0;

}




linux-os (Dick Johnson) wrote:

> For those who think that C/H/S translation is useful,
> attached is a simple program that gets whatever the BIOS
> used from user-space. If you have large media (most do),
> you will descover that C/H/S is useless because it is
> always set to "MAX" like this:
>
> 	Disk parameter table(s) at vector 0x41
> Disk0
>     Cylinders = 1024
>       Sectors = 63
>         Heads = 255
> Write precomp = 0
>  Landing zone = 65296
> 	Reserved bit 0 set
> 	Reserved bit 1 set
> 	Reserved bit 2 set
> 	More than 8 heads
> 	Reserved bit 4 set
> 	Defect map present
> 	Disable retries
> 	Disable retries
> Disk1
>     Cylinders = 306
>       Sectors = 1
>         Heads = 4
> Write precomp = 0
>  Landing zone = 12544
> 	Disk parameter table(s) at vector 0x46
> Disk0
>     Cylinders = 306
>       Sectors = 1
>         Heads = 4
> Write precomp = 0
>  Landing zone = 12544
> Disk1
>     Cylinders = 306
>       Sectors = 1
>         Heads = 4
> Write precomp = 0
>  Landing zone = 12544
>
>
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.15.4 on an i686 machine (5589.55 BogoMips).
> Warning : 98.36% of all statistics are fiction.
> _
> 
>
>
> ****************************************************************
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>
> Thank you.

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