int 13h & greater
 

I'm looking for the method(s) used to access disks with greater than 8 gigabytes capacity
on the IBM style computers, ie Compaq/hp, Dell, etc? I've checked interupt 13h for the
presence of "extended" capabilities but have found nothing on 4 different machines.
There is, obviously, another access path. Anyone know what or where it is.

Hul

int 13h & greater
 

On Thu, 5 Sep 2019 19:25:39 +0000 (UTC), Hul Tytus
wrote:

I'm looking for the method(s) used to access disks with greater than 8 gigabytes capacity
on the IBM style computers, ie Compaq/hp, Dell, etc? I've checked interupt 13h for the
presence of "extended" capabilities but have found nothing on 4 different machines.
There is, obviously, another access path. Anyone know what or where it is.

Try alt.lang.asm.
They love their INT's there.
[]'s
--
Don't be evil - Google 2004
We have a new policy - Google 2012

int 13h & greater
 

Shadow wrote:
On Thu, 5 Sep 2019 19:25:39 +0000 (UTC), Hul Tytus
wrote:

I'm looking for the method(s) used to access disks with greater than 8 gigabytes capacity
on the IBM style computers, ie Compaq/hp, Dell, etc? I've checked interupt 13h for the
presence of "extended" capabilities but have found nothing on 4 different machines.
There is, obviously, another access path. Anyone know what or where it is.

Try alt.lang.asm.
They love their INT's there.
[]'s

http://mbldr.sourceforge.net/specsedd30.pdf

That's around the time I got my first IBM PC.
Up to that time, I'd used Macintosh computers.

My first machine, had a setting for each disk. It
could be set in LBA mode, for the disk drive. Or,
it could be set in something called Large mode.
And it likely had some other flavors perhaps
related to CHS. These probably had something to do
as well, with the Extended INT13 responses.

Also, around that time, disk drives had BIOS limitations
of 64GB or 137GB. Where 137 GB would be "the upper limit
of pre-LBA48 operation, where the LBA was 28 bit and
the drive wasn't "double pumped" to pass a further
extension of LBA address.

The LBA48 was around, maybe 2003 or so. That took drives
to 2TB (based on 32 bit entries in the MBR as being
the final limiting factor).

To go past 2TB, took EFI/UEFI and GPT partitioning,
which presumably has 64 bit pointers and quantities.

There's a progression there, although the best example
is likely to be my P2B-S, which was sorta on the edge
of the transition. Later machines had neither the
"fixation with C: " in the actual BIOS, nor with
showing CHS versus LBA operation at BIOS level.

I expect at some point, the BIOS switched permanently
to LBA mode.

Even though CHS has followed, like a trail of slime
ever since. As the MBR still has CHS fields in it,
even if they're to a large extent, "fake" values.
Tools like my Powerquest Partition Magic 7 still
got incensed about the specific values the OS
was using for CHS fields, and the OS and PM7
used to get in ****ing matches about "who was right".

Today, I can hardly keep PM7 running, as it "sees too much
evil" on the disks, and it just gives up and exits. It's
very picky about geometry specification, and equally unhappy
about disks partitioned on 1MB boundaries. It doesn't know
what to make of those.

Paul