On Sat, 22 Mar 2008 16:27:30 -0700, I waved a wand and this message
magically appears in front of dave:
> Lets start with the formula: 1024 * 256 * 63 * 512 = 8,455,716,864.
> Most BIOSes do not use 1024 and 256, but subtract one from each. That
> is somewhat an artifact of the old IBM AT where the last cylinder was
> never allocated to allow the IBM Advanced Diagnostics to use it for
> read/write testing of the old MFM hard drive.
Yes, that's correct according to the various do***entation I've seen on
the 'net for the AH = 8 / Int 0x13 BIOS calls.
> The extended BIOS functions INT 13h, functions 4Xh allow packets to be
> used to detail larger hard drives. I do not believe that MS-DOS 6.22
> will use that access method, but I know that MS-DOS 7.x does. It
> ****pped with Windows 95, 98, 98SE, and Me in various minor version
> numbers. I believe that IBM DOS was updated to handle this access.
Thanks for reminding me about MSDOS 7.x, I'll look into that as well.
> Most SATA controller vendors probably don't even think about MS-DOS
> anymore. You could write a small device driver that would hook INT
> 13h and for the second drive return a CHS value that is larger. I
> would also consider disabling any ATAPI/IDE controllers on the
> motherboard so the new drive is assigned 80h for the DL value.
They ought to; there's still a lot of people using DOS these days.
> I personally use USB drives to boot MS-DOS whenever I need it, but it
> does require a later motherboard compared to the Pentium III.
Again that's down to the BIOS having the appropriate calls to be able
to boot off CDROMs / USB keys.
Thanks for the information.
I'm now busy on another project; a sub-2k program to scan the PCI bus
and print out all devices on it.
Regards,
Alex
--
http://www.munted.org.uk
Fearsome grindings.
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