Re: C/H/S from user space

["Jeff V. Merkey" <jmerkey@wolfmountaingroup.com>]

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.
>_
>\x1a\x04
>
>
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>Thank you.
>