"Dave Platt" wrote in message
...
What's the best I can do?

All the partition managers tried so far, offer a single partition just
under
750Gb and no remaining unpartitioned space.

A 2Tb drive works just fine - I'd even settle for that from the 3Tb
one..........

I suspect that what you're running into is the 2.2-terabyte limit in
the standard PC Master Boot Record. This would correspond to 32 bits
worth of sectors (4 hexabillion) at 512 bytes each.

Probably, when your partition table is being built, the software
you're using is trying to read the hard drive size via the PC BIOS,
and the sector count is wrapping around past 4 billion. The program
ends up with (3 terabytes - 2.2 terabytes) worth of sectors, and so
you only get 750 GB.

I'm not an expert in the PC BIOS, but I suspect that the "read drive
sector count" call returns a 32-bit result, and the BIOS isn't smart
enough to clip (rather than wrap) at 2.2 terabytes. If that's the
case, no matter what program you use, you'll hit the same behavior.

There's probably a fix, although it won't be trivial. What you would
need to do is let the software partition the drive. If you want more
than one partition, delete the single 750-gig existing one and create
the smaller ones you want at first, and then create a final partition
which uses up the remainder of the 750 GB space.

Then go in with a sector-level disk editing program, and edit the
partition table by hand. Take a look at

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

You'd want to edit the "number of sectors in partition" value at
offset 12 (0x0C) for the last (or only) partition and set it to
"0xFFFFFFFF" (or slightly less than that) and store this entry. This
would expand that partition to 2.2 terabytes.

Save the MBR, reboot, and I think you'd find that you have more space
available.

HOWEVER: depending on how your PC accesses the drive, you could find
that Bad Things happen when it tries to write beyond the 2.2-terabyte
boundary - reads and writes might wrap around to the beginning of the
disk. For that reason, it would probably be safest to limit the total
size of the partitions you create to slightly less than 2.2 terabytes,
so that all of the subsequent I/O operations are compatible with a
32-bit sector-offset API.

Pretty sure something nasty would happen if I tried for more than 2.2Gb
partition - but I can't even get that.

I was thinking more along the lines of 2x 1.5Tb partitions.