DOSFS problems

Tue Mar 9 15:25:57 UTC 2004

Thomas Doerfler wrote:

>Could you possible give the values that are present in your 
>MBR and partition table? It may be that the RTEMS DOSFS code 
>does not implement ALL possible partition types and options.
>
Hi Thomas, thank you again.

The result of all tests is: the simplest possible DOS install always gives
working system disks with a MBR that's never accepted by DOSFS.
For all tested DOS/fdisk/HW/FAT type/ etc etc. combinations:
- HD MBR zeroed before installing DOS
- no disk managers, installed DOS boots from C: and works
- probably DOSFS fails before accessing the partition table:
  * MBR[11,12] of the HD is always wrong (huge, ie: 07 50 instead of 00 20
     and changes using different fdisk/format tools)
  * the final 55 AA signature on the HD MBR is sometimes absent (00 00)
- the initial OEM FIELD on the HD MBR is never an ASCII string ?????
- the partition tab is @ offset 446 ... standard ... DOS works
- the MBR of the install floppy seems always to be "regular"... why it 
is not
   reproduced (with the obvious changes) on the HD ???

Forcing rigth values in the DOSFS source don't work.
Clearly there are other inconsistent values in the MBR.

If this info are not precise enough I'll send some MBR dumps.
It's not immediate to transfer them to my PC.

Is there any other rtems-user who had a similar problem ?
Using very standard but quite old HW can be a problem ?
Is there any particular DOS install procedure/trick/option to
force the layout of  the MBR of the HD ?

Adriano

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Date:	Tue, 09 Mar 2004 18:34:53 +0300
From:	"Victor V. Vengerov" <vvv at oktetlabs.ru>
Organization: OKTET Labs.
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To:	Adriano Verardo <a.verardo at tecmav.fastwebnet.it>
CC:	Thomas Doerfler <Thomas.Doerfler at imd-systems.de>,
	rtems-users <rtems-users at rtems.com>
Subject: Re: DOSFS problems
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Adriano,

As fine as I understand you need proper MBR on your HDD to run
dosfs test.

As I remember, you may re-initialize MBR on your HDD invoking

fdisk /mbr
(or fdisk C: /mbr ?)

Then, run fdisk C: and ensure that your partition table is correct.
If problem persists, try to reduce partition size to, let say, 256Mb
using fdisk.

Regards,
Victor

Adriano Verardo wrote:

> Thomas Doerfler wrote:
>
>> Could you possible give the values that are present in your MBR and 
>> partition table? It may be that the RTEMS DOSFS code does not 
>> implement ALL possible partition types and options.
>>
> Hi Thomas, thank you again.
>
> The result of all tests is: the simplest possible DOS install always 
> gives
> working system disks with a MBR that's never accepted by DOSFS.
> For all tested DOS/fdisk/HW/FAT type/ etc etc. combinations:
> - HD MBR zeroed before installing DOS
> - no disk managers, installed DOS boots from C: and works
> - probably DOSFS fails before accessing the partition table:
>  * MBR[11,12] of the HD is always wrong (huge, ie: 07 50 instead of 00 20
>     and changes using different fdisk/format tools)
>  * the final 55 AA signature on the HD MBR is sometimes absent (00 00)
> - the initial OEM FIELD on the HD MBR is never an ASCII string ?????
> - the partition tab is @ offset 446 ... standard ... DOS works
> - the MBR of the install floppy seems always to be "regular"... why it 
> is not
>   reproduced (with the obvious changes) on the HD ???
>
> Forcing rigth values in the DOSFS source don't work.
> Clearly there are other inconsistent values in the MBR.
>
> If this info are not precise enough I'll send some MBR dumps.
> It's not immediate to transfer them to my PC.
>
> Is there any other rtems-user who had a similar problem ?
> Using very standard but quite old HW can be a problem ?
> Is there any particular DOS install procedure/trick/option to
> force the layout of  the MBR of the HD ?
>
> Adriano
>
>
>
>
>

-- 
Victor V. Vengerov
OKTET Labs.
Phone: mobile +7 812 9389372, home +7 812 4281653 