f



booting won't work

    I know this doesn't work, and I've tried it. Just to see what happens. I 
copied from a .VHD file containing a MBR and BS of DOS 6.21 and copied the 
MBR to my computer's MBR. Is it because of today's architecture or the code 
itself that won't allow today's machines to properly load? I would think the 
BS's first 3 bytes is x86 jump opcode.

Bill


0
Bill
12/21/2016 10:18:16 PM
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Bill Cunningham <nospam@nspam.invalid> wrote:
>    I know this doesn't work, and I've tried it. Just to see what happens. I 
>copied from a .VHD file containing a MBR and BS of DOS 6.21 and copied the 
>MBR to my computer's MBR. Is it because of today's architecture or the code 
>itself that won't allow today's machines to properly load? I would think the 
>BS's first 3 bytes is x86 jump opcode.

The MBR also contains the MBR partition table, so if you did in fact do
that it's not surpring it didn't work, as you would've overwriten your
computer partition table with that of your virtual hard drive image's.

This above assumes your computer's drive was uses an MBR partition
table. If instead you have UEFI BIOS and the drive has a GPT partion
table then there's no MBR on your hard drive.  When booting a GPT disk
with a UEFI BIOS the MBR, the first sector on the drive, isn't used.
Instead it uses a different booting mechanism.  There's a fake MBR sector
at the start of the drive, but that's only there to discourage older
software that doesn't understand GPT partition from messing with the disk.
Overwriting it with a real MBR from your VHD would have no effect.

					Ross Ridge

-- 
 l/  //	  Ross Ridge -- The Great HTMU
[oo][oo]  rridge@csclub.uwaterloo.ca
-()-/()/  http://www.csclub.uwaterloo.ca/~rridge/ 
 db  //	  
0
rridge
12/22/2016 1:09:56 AM
On Wed, 21 Dec 2016 17:18:16 -0500
"Bill Cunningham" <nospam@nspam.invalid> wrote:

>     I know this doesn't work, and I've tried it. Just to see what
> happens. I copied from a .VHD file containing a MBR and BS of DOS
> 6.21 and copied the MBR to my computer's MBR. Is it because of
> today's architecture or the code itself that won't allow today's
> machines to properly load? I would think the BS's first 3 bytes is
> x86 jump opcode.

What is a .VHD file? ...

https://en.wikipedia.org/wiki/VHD_(file_format)

Wikipedia's description of the supported VHD image formats don't seem to
match what is used for a real hard drive, such as when using MS-DOS
6.22, MS-DOS 5.00, etc.  I.e., they seem to be specialized formats and
I'd assume they probably have code which doesn't work with real devices.

For hard drive media, DOS uses MBR code that supports partitions, and
VBR/PBR code to boot specific partitions.  This is different from the
code used to boot floppies.  Floppies don't have partitions or VBR/PBR
code or 0xAA55 signatures.

IIRC, the way to set up a new hard drive for MS-DOS is to first use
FDISK on the drive to create partitions.  FDISK can create a few
different types of (primary) DOS FAT filesystems (FAT12, FAT16, perhaps
FAT32) and extended (or logical) DOS partitions.  FDISK is then used to
set a primary partition to be the active partition, which means
bootable.  After a reboot, DOS recognizes the drive.  Then, you can use
FORMAT to format a partition.  Finally, to install MS-DOS system files
(COMMAND.COM, IO.SYS, MSDOS.SYS) to specific sectors, you use the SYS
command.

Other than new (non-MBR) GPT partitions that Ross mentioned, the only
other issue I know of where valid MBR boot code won't boot, is for
bootable floppies or a USB drive/stick with a bootable floppy image.
Around 2007 or so, the BIOS of some machines began to require an 0xAA55
signature for bootable floppies and bootable floppy images written to
USB drives or USB sticks.  This 0xAA55 signature was _NOT_ a requirement
for floppies according to the original IBM PC Technical Reference
manuals.  CP/M disks also booted without having this signature.  If this
"new" behavior is part of some specification which obsoleted the earlier
behavior, I've yet to find it documented anywhere, or be told of the
document.  (I know there was one guy I ran into around 2007 who
adamantly argued that the signature was required for floppies, but
couldn't prove it.  He was very pro-M$.  So, maybe it was part of some
M$ requirement.  He "disappeared" after I posted the IBM Tech. Ref.
info.  I don't recall which newsgroup that was.)

https://en.wikipedia.org/wiki/Master_boot_record
https://en.wikipedia.org/wiki/Volume_boot_record
https://en.wikipedia.org/wiki/GUID_Partition_Table


Rod Pemberton
PS.  It seems I need to get back to you on those links to files.

0
Rod
12/22/2016 1:35:09 AM
"Rod Pemberton" <NeedNotReplyHere@xrsevnneqk.cem> wrote in message 
news:20161221203509.2b383b6d@_...
> On Wed, 21 Dec 2016 17:18:16 -0500
> "Bill Cunningham" <nospam@nspam.invalid> wrote:
>
>>     I know this doesn't work, and I've tried it. Just to see what
>> happens. I copied from a .VHD file containing a MBR and BS of DOS
>> 6.21 and copied the MBR to my computer's MBR. Is it because of
>> today's architecture or the code itself that won't allow today's
>> machines to properly load? I would think the BS's first 3 bytes is
>> x86 jump opcode.
>
> What is a .VHD file? ...
>
> https://en.wikipedia.org/wiki/VHD_(file_format)
>
> Wikipedia's description of the supported VHD image formats don't seem to
> match what is used for a real hard drive, such as when using MS-DOS
> 6.22, MS-DOS 5.00, etc.  I.e., they seem to be specialized formats and
> I'd assume they probably have code which doesn't work with real devices.
>
> For hard drive media, DOS uses MBR code that supports partitions, and
> VBR/PBR code to boot specific partitions.  This is different from the
> code used to boot floppies.  Floppies don't have partitions or VBR/PBR
> code or 0xAA55 signatures.
>
> IIRC, the way to set up a new hard drive for MS-DOS is to first use
> FDISK on the drive to create partitions.  FDISK can create a few
> different types of (primary) DOS FAT filesystems (FAT12, FAT16, perhaps
> FAT32) and extended (or logical) DOS partitions.  FDISK is then used to
> set a primary partition to be the active partition, which means
> bootable.  After a reboot, DOS recognizes the drive.  Then, you can use
> FORMAT to format a partition.  Finally, to install MS-DOS system files
> (COMMAND.COM, IO.SYS, MSDOS.SYS) to specific sectors, you use the SYS
> command.
>
> Other than new (non-MBR) GPT partitions that Ross mentioned, the only
> other issue I know of where valid MBR boot code won't boot, is for
> bootable floppies or a USB drive/stick with a bootable floppy image.
> Around 2007 or so, the BIOS of some machines began to require an 0xAA55
> signature for bootable floppies and bootable floppy images written to
> USB drives or USB sticks.  This 0xAA55 signature was _NOT_ a requirement
> for floppies according to the original IBM PC Technical Reference
> manuals.  CP/M disks also booted without having this signature.  If this
> "new" behavior is part of some specification which obsoleted the earlier
> behavior, I've yet to find it documented anywhere, or be told of the
> document.  (I know there was one guy I ran into around 2007 who
> adamantly argued that the signature was required for floppies, but
> couldn't prove it.  He was very pro-M$.  So, maybe it was part of some
> M$ requirement.  He "disappeared" after I posted the IBM Tech. Ref.
> info.  I don't recall which newsgroup that was.)
>
> https://en.wikipedia.org/wiki/Master_boot_record
> https://en.wikipedia.org/wiki/Volume_boot_record
> https://en.wikipedia.org/wiki/GUID_Partition_Table
>
>
> Rod Pemberton
> PS.  It seems I need to get back to you on those links to files.

    It's MS's virtual hard disk format. With their virtual PC emulator. 
Right it has it's own format. But in a hexdump I recognized the MBR and BS 
of an MS-DOS setup. So I used dd to pull out the MBR and BS or Vol boot 
record code. I inserted a real old msdos 6.22 MBR in the first sector and it 
didn't work. Everything was backed up of course. I can send you a bit of 
binary code if you want to look at it yourself. The first bit of the file is 
Virtual PC format. And later in the file is the code we used years ago. A 
MBR indicating a 16 bit partition. I think that might be it. Not sure. And a 
volume boot sector later in the .vhd file.

Bill


0
Bill
12/22/2016 5:55:21 PM
On Thu, 22 Dec 2016 12:55:21 -0500
"Bill Cunningham" <nospam@nspam.invalid> wrote:

> "Rod Pemberton" <NeedNotReplyHere@xrsevnneqk.cem> wrote in message 
> news:20161221203509.2b383b6d@_...
> > On Wed, 21 Dec 2016 17:18:16 -0500
> > "Bill Cunningham" <nospam@nspam.invalid> wrote:

> >>     I know this doesn't work, and I've tried it. Just to see what
> >> happens. I copied from a .VHD file containing a MBR and BS of DOS
> >> 6.21 and copied the MBR to my computer's MBR. Is it because of
> >> today's architecture or the code itself that won't allow today's
> >> machines to properly load? I would think the BS's first 3 bytes is
> >> x86 jump opcode.  
> >
> > What is a .VHD file? ...
> >
>
>     It's MS's virtual hard disk format. With their virtual PC
> emulator. Right it has it's own format. But in a hexdump I recognized
> the MBR and BS of an MS-DOS setup. So I used dd to pull out the MBR
> and BS or Vol boot record code. I inserted a real old msdos 6.22 MBR
> in the first sector and it didn't work. Everything was backed up of
> course. I can send you a bit of binary code if you want to look at it
> yourself. The first bit of the file is Virtual PC format. And later
> in the file is the code we used years ago. A MBR indicating a 16 bit
> partition. I think that might be it. Not sure. And a volume boot
> sector later in the .vhd file.
> 

I'm not real clear on what you're trying to do ... or why.

You can easily create new DOS partitions and format them from DOS using
FDISK, FORMAT, and SYS.

You can easily create new DOS partitions and format them from Linux
using Linux fdisk, mkfs.vfat, and ms-sys, or via combinations of other
Linux tools

You can also easily create DOS filesystem images easily from Linux.

So, why do you need to use whatever code is in the .VHD file?  Is
this just for personal experimentation?


Rod Pemberton

0
Rod
12/23/2016 12:58:29 AM
"Rod Pemberton" <NeedNotReplyHere@xrsevnneqk.cem> wrote in message 
news:20161222195829.484e6a0d@_...
> On Thu, 22 Dec 2016 12:55:21 -0500
> "Bill Cunningham" <nospam@nspam.invalid> wrote:
>
>> "Rod Pemberton" <NeedNotReplyHere@xrsevnneqk.cem> wrote in message
>> news:20161221203509.2b383b6d@_...
>> > On Wed, 21 Dec 2016 17:18:16 -0500
>> > "Bill Cunningham" <nospam@nspam.invalid> wrote:
>
>> >>     I know this doesn't work, and I've tried it. Just to see what
>> >> happens. I copied from a .VHD file containing a MBR and BS of DOS
>> >> 6.21 and copied the MBR to my computer's MBR. Is it because of
>> >> today's architecture or the code itself that won't allow today's
>> >> machines to properly load? I would think the BS's first 3 bytes is
>> >> x86 jump opcode.
>> >
>> > What is a .VHD file? ...
>> >
>>
>>     It's MS's virtual hard disk format. With their virtual PC
>> emulator. Right it has it's own format. But in a hexdump I recognized
>> the MBR and BS of an MS-DOS setup. So I used dd to pull out the MBR
>> and BS or Vol boot record code. I inserted a real old msdos 6.22 MBR
>> in the first sector and it didn't work. Everything was backed up of
>> course. I can send you a bit of binary code if you want to look at it
>> yourself. The first bit of the file is Virtual PC format. And later
>> in the file is the code we used years ago. A MBR indicating a 16 bit
>> partition. I think that might be it. Not sure. And a volume boot
>> sector later in the .vhd file.
>>
>
> I'm not real clear on what you're trying to do ... or why.
>
> You can easily create new DOS partitions and format them from DOS using
> FDISK, FORMAT, and SYS.
>
> You can easily create new DOS partitions and format them from Linux
> using Linux fdisk, mkfs.vfat, and ms-sys, or via combinations of other
> Linux tools
>
> You can also easily create DOS filesystem images easily from Linux.
>
> So, why do you need to use whatever code is in the .VHD file?  Is
> this just for personal experimentation?

    It is indeed for personal experimentation. And if you will notice with 
tools like mkfs.vfat and so on, there will be large empty areas in the BS 
and MBR with MS's signatures and such. The mkfs.vaft isn't a MS formatter.
    So you can install on today's machines with fdisk.exe and format.com a 
MS-DOS 6.22 partition? Hum. I didn't know that. So why do we use virtual 
machines like Virt PC and virtualbox, and qemu?

    I can run msdos 6.22 beside XP n two different partitions? IDK about 
that.

Bill


0
Bill
12/23/2016 5:33:57 PM
"Bill Cunningham" wrote:
....

> So you can install on today's machines with fdisk.exe and format.com a 
> MS-DOS 6.22 partition? Hum. I didn't know that. So why do we use virtual 
> machines like Virt PC and virtualbox, and qemu?
 
> I can run msdos 6.22 beside XP n two different partitions? IDK about 
> that.

You cannot add a bootable DOS-partition after XP-installation.

You can have DOS and XP one one harddisk, but you need to:

1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
  extended partition where a larger logical drive for XP can reside.

2.make the first partition an Active one and name it ie:"DOS"

3. insert your XP-install CD into the drive.
 
4.install DOS and reboot but intercept the boot be pressing F11-key.
 
5.select from BIOS-setup option to boot from CD.
  follow the on screen advice and select the free space after 
  your DOS-partition when XP asks 'where to' install.

this way XP creates a small bootloader which let you chose on every 
boot to run XP or your old DOS (in true real mode).

  !!! Warning !!! 
"true real mode" is quite different to the XP-DOS-box and if you play 
around with the MBR then ALL partitions will be destroyed.

And this is the main reason for you better use a virtual environment.
__
wolfgang 
0
wolfgang
12/24/2016 12:11:40 PM
"wolfgang kern" <nowhere@never.at> wrote in message 
news:o3lom9$1br8$1@gioia.aioe.org...

> You cannot add a bootable DOS-partition after XP-installation.
>
> You can have DOS and XP one one harddisk, but you need to:
>
> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
> extended partition where a larger logical drive for XP can reside.
>
> 2.make the first partition an Active one and name it ie:"DOS"
>
> 3. insert your XP-install CD into the drive.
>
> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>
> 5.select from BIOS-setup option to boot from CD.
>  follow the on screen advice and select the free space after your 
> DOS-partition when XP asks 'where to' install.
>
> this way XP creates a small bootloader which let you chose on every boot 
> to run XP or your old DOS (in true real mode).
>
>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box and 
> if you play around with the MBR then ALL partitions will be destroyed.
>
> And this is the main reason for you better use a virtual environment.

    Don't these same rules apply if you were installing a side by side 
install of win 98 or such.

Bill


0
Bill
12/24/2016 4:35:08 PM
On Sat, 24 Dec 2016 11:35:08 -0500, Bill Cunningham wrote:

> "wolfgang kern" <nowhere@never.at> wrote in message 
> news:o3lom9$1br8$1@gioia.aioe.org...
> 
>> You cannot add a bootable DOS-partition after XP-installation.
>>
>> You can have DOS and XP one one harddisk, but you need to:
>>
>> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
>> extended partition where a larger logical drive for XP can reside.
>>
>> 2.make the first partition an Active one and name it ie:"DOS"
>>
>> 3. insert your XP-install CD into the drive.
>>
>> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>>
>> 5.select from BIOS-setup option to boot from CD.
>>  follow the on screen advice and select the free space after your 
>> DOS-partition when XP asks 'where to' install.
>>
>> this way XP creates a small bootloader which let you chose on every boot 
>> to run XP or your old DOS (in true real mode).
>>
>>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box and 
>> if you play around with the MBR then ALL partitions will be destroyed.
>>
>> And this is the main reason for you better use a virtual environment.
> 
>     Don't these same rules apply if you were installing a side by side 
> install of win 98 or such.
> 
> Bill

Several years ago I have a P1 system with DOS 6.22 on a 2gig drive.
I added a second drive that was around 20gig IIRC.  Booted with the
Win98 boot floppy and started the Win98 install.  When it asked for
the installation directory I pointed it to D:\WINDOWS.  After the
install I rebooted and there was a config.sys boot menu for DOS and
Win98 that was created automatically.

-- 
<Wildman> GNU/Linux user #557453
The cow died so I don't need your bull!
0
Wildman
12/24/2016 5:28:53 PM
"wolfgang kern" <nowhere@never.at> wrote in message 
news:o3lom9$1br8$1@gioia.aioe.org...

> You cannot add a bootable DOS-partition after XP-installation.
>
> You can have DOS and XP one one harddisk, but you need to:
>
> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
> extended partition where a larger logical drive for XP can reside.
>
> 2.make the first partition an Active one and name it ie:"DOS"
>
> 3. insert your XP-install CD into the drive.
>
> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>
> 5.select from BIOS-setup option to boot from CD.
>  follow the on screen advice and select the free space after your 
> DOS-partition when XP asks 'where to' install.
>
> this way XP creates a small bootloader which let you chose on every boot 
> to run XP or your old DOS (in true real mode).
>
>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box and 
> if you play around with the MBR then ALL partitions will be destroyed.
>
> And this is the main reason for you better use a virtual environment.

 You speak of an extended partition. Would it "contain" the NTFS filesytem? 
And I could put maybe a 83h or 0x83 partition after that? I understand DOS 
wants that first sector. 500M you say. I know FAT16 can handle up to about 2 
GB. But how much can MS's old format.com format?

Bill


0
Bill
12/24/2016 7:59:41 PM
"Wildman" <best_lay@yahoo.com> wrote in message 
news:NaudnVCq0sTILcPFnZ2dnUU7-eOdnZ2d@giganews.com...
> On Sat, 24 Dec 2016 11:35:08 -0500, Bill Cunningham wrote:
>
>> "wolfgang kern" <nowhere@never.at> wrote in message
>> news:o3lom9$1br8$1@gioia.aioe.org...
>>
>>> You cannot add a bootable DOS-partition after XP-installation.
>>>
>>> You can have DOS and XP one one harddisk, but you need to:
>>>
>>> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an
>>> extended partition where a larger logical drive for XP can reside.
>>>
>>> 2.make the first partition an Active one and name it ie:"DOS"
>>>
>>> 3. insert your XP-install CD into the drive.
>>>
>>> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>>>
>>> 5.select from BIOS-setup option to boot from CD.
>>>  follow the on screen advice and select the free space after your
>>> DOS-partition when XP asks 'where to' install.
>>>
>>> this way XP creates a small bootloader which let you chose on every boot
>>> to run XP or your old DOS (in true real mode).
>>>
>>>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box 
>>> and
>>> if you play around with the MBR then ALL partitions will be destroyed.
>>>
>>> And this is the main reason for you better use a virtual environment.
>>
>>     Don't these same rules apply if you were installing a side by side
>> install of win 98 or such.
>>
>> Bill
>
> Several years ago I have a P1 system with DOS 6.22 on a 2gig drive.
> I added a second drive that was around 20gig IIRC.  Booted with the
> Win98 boot floppy and started the Win98 install.  When it asked for
> the installation directory I pointed it to D:\WINDOWS.  After the
> install I rebooted and there was a config.sys boot menu for DOS and
> Win98 that was created automatically.

    Here's my problem. I have no floppies they went a long time ago. I have 
..img files and an iso that is supposed to boot dos 6.22 and doesn't. IDK how 
to install it on an actual machine now.

Bill


0
Bill
12/24/2016 9:29:29 PM
"Bill Cunningham" asked:

>> You cannot add a bootable DOS-partition after XP-installation.

>> You can have DOS and XP one one harddisk, but you need to:
>>
>> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
>> extended partition where a larger logical drive for XP can reside.
>>
>> 2.make the first partition an Active one and name it ie:"DOS"
>>
>> 3. insert your XP-install CD into the drive.
>>
>> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>>
>> 5.select from BIOS-setup option to boot from CD.
>>  follow the on screen advice and select the free space after your 
>> DOS-partition when XP asks 'where to' install.

>> this way XP creates a small bootloader which let you chose on every boot 
>> to run XP or your old DOS (in true real mode).

>>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box 
>> and if you play around with the MBR then ALL partitions will be 
>> destroyed.

>> And this is the main reason for you better use a virtual environment.


> You speak of an extended partition. Would it "contain" the NTFS filesytem?

No, the XP-installer will ask you if it shall format the free space
after your DOS-partition either FAT32 or NTFS (XP works on both).

> And I could put maybe a 83h or 0x83 partition after that?

No, you would need a better than DOS formatting tool like PQmagic
to create Loonix partitions.

> I understand DOS  wants that first sector. 500M you say.

yes.

> I know FAT16 can handle up to about 2 GB.

yes, but expect a high waste with that cluster-size.

> But how much can MS's old format.com format?

depends on "how old".
FDISK format on my DOS6.00 is limited to 8GB (even CHS max.= 127GB).
__
wolfgang 

0
wolfgang
12/25/2016 12:01:05 AM
On Sat, 24 Dec 2016 16:29:29 -0500, Bill Cunningham wrote:

> "Wildman" <best_lay@yahoo.com> wrote in message 
> news:NaudnVCq0sTILcPFnZ2dnUU7-eOdnZ2d@giganews.com...
>> On Sat, 24 Dec 2016 11:35:08 -0500, Bill Cunningham wrote:
>>
>>> "wolfgang kern" <nowhere@never.at> wrote in message
>>> news:o3lom9$1br8$1@gioia.aioe.org...
>>>
>>>> You cannot add a bootable DOS-partition after XP-installation.
>>>>
>>>> You can have DOS and XP one one harddisk, but you need to:
>>>>
>>>> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an
>>>> extended partition where a larger logical drive for XP can reside.
>>>>
>>>> 2.make the first partition an Active one and name it ie:"DOS"
>>>>
>>>> 3. insert your XP-install CD into the drive.
>>>>
>>>> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>>>>
>>>> 5.select from BIOS-setup option to boot from CD.
>>>>  follow the on screen advice and select the free space after your
>>>> DOS-partition when XP asks 'where to' install.
>>>>
>>>> this way XP creates a small bootloader which let you chose on every boot
>>>> to run XP or your old DOS (in true real mode).
>>>>
>>>>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box 
>>>> and
>>>> if you play around with the MBR then ALL partitions will be destroyed.
>>>>
>>>> And this is the main reason for you better use a virtual environment.
>>>
>>>     Don't these same rules apply if you were installing a side by side
>>> install of win 98 or such.
>>>
>>> Bill
>>
>> Several years ago I have a P1 system with DOS 6.22 on a 2gig drive.
>> I added a second drive that was around 20gig IIRC.  Booted with the
>> Win98 boot floppy and started the Win98 install.  When it asked for
>> the installation directory I pointed it to D:\WINDOWS.  After the
>> install I rebooted and there was a config.sys boot menu for DOS and
>> Win98 that was created automatically.
> 
>     Here's my problem. I have no floppies they went a long time ago. I have 
> .img files and an iso that is supposed to boot dos 6.22 and doesn't. IDK how 
> to install it on an actual machine now.
> 
> Bill

If you have the capability of booting from a CD, email me at
the Yahoo address.  I have a solution.

-- 
<Wildman> GNU/Linux user #557453
The cow died so I don't need your bull!
0
Wildman
12/25/2016 5:48:46 AM
On Sun, 25 Dec 2016 01:01:05 +0100, wolfgang kern wrote:

> "Bill Cunningham" asked:
> 
>>> You cannot add a bootable DOS-partition after XP-installation.
> 
>>> You can have DOS and XP one one harddisk, but you need to:
>>>
>>> 1.format it with a first partition for DOS (ie: FAT16, 500MB) and an 
>>> extended partition where a larger logical drive for XP can reside.
>>>
>>> 2.make the first partition an Active one and name it ie:"DOS"
>>>
>>> 3. insert your XP-install CD into the drive.
>>>
>>> 4.install DOS and reboot but intercept the boot be pressing F11-key.
>>>
>>> 5.select from BIOS-setup option to boot from CD.
>>>  follow the on screen advice and select the free space after your 
>>> DOS-partition when XP asks 'where to' install.
> 
>>> this way XP creates a small bootloader which let you chose on every boot 
>>> to run XP or your old DOS (in true real mode).
> 
>>>  !!! Warning !!! "true real mode" is quite different to the XP-DOS-box 
>>> and if you play around with the MBR then ALL partitions will be 
>>> destroyed.
> 
>>> And this is the main reason for you better use a virtual environment.
> 
> 
>> You speak of an extended partition. Would it "contain" the NTFS filesytem?
> 
> No, the XP-installer will ask you if it shall format the free space
> after your DOS-partition either FAT32 or NTFS (XP works on both).
> 
>> And I could put maybe a 83h or 0x83 partition after that?
> 
> No, you would need a better than DOS formatting tool like PQmagic
> to create Loonix partitions.
> 
>> I understand DOS  wants that first sector. 500M you say.
> 
> yes.
> 
>> I know FAT16 can handle up to about 2 GB.
> 
> yes, but expect a high waste with that cluster-size.
> 
>> But how much can MS's old format.com format?
> 
> depends on "how old".
> FDISK format on my DOS6.00 is limited to 8GB (even CHS max.= 127GB).
> __
> wolfgang

According to MS the maximum drive size for FAT16 file systems is 4gig
with a maximum partition size of 2gig.

https://support.microsoft.com/en-us/kb/118335

-- 
<Wildman> GNU/Linux user #557453
The cow died so I don't need your bull!
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Wildman
12/25/2016 5:57:37 AM
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