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From: Barry Watzman on 8 May 2010 10:32
SOME computers that use IDE hard drives have size limit of 137 [decimal]
gigabytes due to something called "48-bit LBA". Not all computers have
this limit; sometimes it can be circumvented if present, other times not.

If your computer has this limit, you can still almost certainly go to
120GB. If you don't have this limit, I think that the largest IDE
laptop drives made were 320GB.

Ron wrote:
>
> John, you could be right.
>
> I didn't even get a manual with the laptop; just a file that I printed
> out. That wasn't very helpful but I came across a discussion about
> replacing Dell hard drives where somebody wanted to know what's the
> biggest hard drive that can be installed on a Dell -- apparently 100
> Gb-- so it has been suggested that because of this limitation the
> system uses IDE drives.
>
>
> Thanks, for the 411 guys; the info is much appreciated. :-)
>
> Ron
>
>
>
>
From: BillW50 on 8 May 2010 12:33
In news:hs3sln$9j5$1(a)news.eternal-september.org,
Barry Watzman typed on Sat, 08 May 2010 10:32:22 -0400:
> SOME computers that use IDE hard drives have size limit of 137
> [decimal] gigabytes due to something called "48-bit LBA". Not all
> computers have this limit; sometimes it can be circumvented if
> present, other times not.
> If your computer has this limit, you can still almost certainly go to
> 120GB. If you don't have this limit, I think that the largest IDE
> laptop drives made were 320GB.

The OS also has to have LBA support too. I am pretty sure any OS after
2004 or 2005 has 48-bit LBA built in. This includes Windows 2000 with
SP3 and SP4 and Windows XP SP1, SP2, and SP3. Windows 98 for example,
has no 48-bit LBA support AFAIK, so you are stuck there without some
sort of clever boot utility.

If your BIOS doesn't support 48-bit LBA, not to worry! The workaround is
simply this. Just divide up your hard drive into two or more partitions.
The boot partition (which usually has the system files on it too), has
to fall within the first 137GB limit.

If you don't partition it this way, Windows or whatever OS you are using
that supports 48-bit LBA will see the whole drive anyway and things
might appear normal. Just the BIOS can't see the whole thing (if your
BIOS doesn't support 48-bit LBA).

But don't be fooled that everything is just fine without partitioning.
As a defrag program or Windows itself will at some point in the future
will move one key boot file past the 137GB limit and then the BIOS can't
boot the OS. Then you are sort of stuck. Fixable, but in involves a lot
of work.

Better to just partition the first boot/system partition within the
first 137GB limits and then you should have no problems whatsoever at
all.

--
Bill
Gateway M465e ('06 era) - Windows XP SP3


From: Barry Watzman on 8 May 2010 15:28
Partitioning is not an answer to the 48-bit LBA issue, at least not if
you were trying to say that he could then use the rest of the drive
(beyond 137GB) in another partition.

This limitation is partially hardware; to address more than 137GB (what
partition it's in notwithstanding and being irrelevant), the IDE port
has to communicate an LBA sector address of more than 48 bits. Some of
them cannot do that. The ***HARDWARE*** cannot do it, PERIOD. It has
48 bit registers in the IDE controller, and it just will not be able to
deal with any part of a drive beyond 137GB. And, what's worse, if it
tries to, the I/O request will "wrap around", back to the start of the
drive, and, likely, will "clobber" the MBR and partition tables, which
is catastrophic.

[If, on the other hand, you are proposing that he only use the 1st 137GB
and not use the rest at all ... then sure, that will work.]

On a desktop, there is another option ... use a controller other than
the one on the motherboard that supports larger drives. For example a
PCI controller. Or even a SCSI or USB or Firewire controller. The
problem is that not all motherboards can boot from such devices and, in
any case, it's usually not an option for a laptop.

BillW50 wrote:
>
> If your BIOS doesn't support 48-bit LBA, not to worry! The workaround is
> simply this. Just divide up your hard drive into two or more partitions.
> The boot partition (which usually has the system files on it too), has
> to fall within the first 137GB limit.
>
> If you don't partition it this way, Windows or whatever OS you are using
> that supports 48-bit LBA will see the whole drive anyway and things
> might appear normal. Just the BIOS can't see the whole thing (if your
> BIOS doesn't support 48-bit LBA).
>
> But don't be fooled that everything is just fine without partitioning.
> As a defrag program or Windows itself will at some point in the future
> will move one key boot file past the 137GB limit and then the BIOS can't
> boot the OS. Then you are sort of stuck. Fixable, but in involves a lot
> of work.
>
> Better to just partition the first boot/system partition within the
> first 137GB limits and then you should have no problems whatsoever at
> all.
>
From: BillW50 on 8 May 2010 17:17
In news:hs4e1s$p2l$1(a)news.eternal-september.org,
Barry Watzman typed on Sat, 08 May 2010 15:28:57 -0400:
> Partitioning is not an answer to the 48-bit LBA issue, at least not if
> you were trying to say that he could then use the rest of the drive
> (beyond 137GB) in another partition.

Yes this is what I was saying.

> This limitation is partially hardware; to address more than 137GB
> (what partition it's in notwithstanding and being irrelevant), the
> IDE port has to communicate an LBA sector address of more than 48
> bits. Some of them cannot do that. The ***HARDWARE*** cannot do it,
> PERIOD. It has 48 bit registers in the IDE controller, and it just
> will not be able to deal with any part of a drive beyond 137GB. And,
> what's worse, if it tries to, the I/O request will "wrap around",
> back to the start of the drive, and, likely, will "clobber" the MBR
> and partition tables, which is catastrophic.

Well that could be I suppose. But all of the ones I have seen was
limited by the BIOS alone. The hardware itself could see the whole thing
(larger than 137GB) just fine. Once a Windows boots that supports 48-bit
LBA, if the hardware (aka controller) couldn't handle it. I would think
that Windows couldn't see the whole drive either. But I could be wrong.

If the BIOS is the only problem. I am sure it is okay just using the
boot/system on a partition in the first 137GB works just fine. As I have
done this many times without a problem. And I have done this with
computers made in 2000 and later. And once the OS boots, it can see the
rest of it without any problems on another partition(s).

I have a couple of Toshiba 2595XDVD from '99 right here. They came with
6GB HDD and I never had anything larger than 60GB in them. And if I
remember right, the 48-bit LBA started in 2002. But I would be more than
happy to throw a spare 160GB HDD in there and report what happens if you
would like.

Those Toshiba 2595XDVD doesn't run Windows 2000/XP very well (they came
with Windows 98FE). Since they are limited to 192MB max memory anyway
(64GB on the motherboard and a 128MB max memory card). Although anything
that can run Windows 2000/XP well enough, I don't think you should have
a problem with the controller. And you need Windows 2000/XP at least to
support 48-bit LBA or the Windows OS can't see it anyway. See what I
mean?

> [If, on the other hand, you are proposing that he only use the 1st
> 137GB and not use the rest at all ... then sure, that will work.]

Well I wasn't really thinking that way. Although the price between a
120GB HDD and a 160GB is almost the same price. So why not go with the
160GB instead? And in some cases, the 160GB might be cheaper anyway.

> On a desktop, there is another option ... use a controller other than
> the one on the motherboard that supports larger drives. For example a
> PCI controller. Or even a SCSI or USB or Firewire controller. The
> problem is that not all motherboards can boot from such devices and,
> in any case, it's usually not an option for a laptop.

Yes this is true in many cases.

--
Bill
Gateway M465e ('06 era) - Windows XP SP3


From: Barry Watzman on 8 May 2010 18:01
Re: "But all of the ones I have seen was limited by the BIOS alone."

No, the actual IDE port hardware itself can make bypassing the 137 GB
barrier impossible. There are address registers in the hardware that
may not support 48-bit LBA addressing. [BTW, the scheme which preceded
48-bit LBA, which limits you to 137GB, was 28-bit LBA]

Partitioning is not a solution in the sense that you were proposing,
although it can let you use only the 1st 137GB of a larger drive (the
rest being entirely and completely unused). This has to be done with
care, because if the OS attempts a write beyond 137GB, you can be hosed.

Of course, there are systems in which the only limitations are the OS or
the BIOS.
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