[1090] in winnt
Re: BIOS limits to disk sizes
daemon@ATHENA.MIT.EDU (Kerem B Limon)
Mon Apr 28 17:46:21 2003
Message-Id: <5.2.0.9.2.20030428161143.04e02120@po11.mit.edu>
Date: Mon, 28 Apr 2003 17:46:02 -0400
To: Dave Broderick <djbroder@mit.edu>
From: Kerem B Limon <kerem.limon@MIT.EDU>
Cc: winpartners@mit.edu
In-Reply-To: <5.0.2.1.2.20030424143906.018d01e0@hesiod>
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Dave--
At 03/04/24 15:12 Thursday, Dave Broderick wrote:
>I used to sort of know this.
>Back in the "old days" 486's had disk drive limits of 512MB. Then, with
>Pentium I , there were 1,2,4 and 8 Gig limits, then, around Pentium II
>time, practical limits started to go away. By Pentium III time (perhaps
>before) you could pretty much install whatever you could by in a store.
>
>Once in a while, I'm tempted to resurrect an older machine and install a
>bigger hard drive. The "kudge test" is to put the newer drive into
>machine. If the BIOS reports the correct values for the drive size, I'm
>probably OK, if not I take it out. I had an old machine once, and i put a
>20gig drive into it. It reported a 14gig drive. "Well, what the heck", I
>thought. Sure enough, files would mysteriously disappear.
>
>Anyone know of a more scientific way to test a machine for disk capacity?
There are 7 major disk capacity limitations: 504 MB, 2.0 GB (2,048 MB), 4.2
GB, 8.4 GB, 32 GB, 64 GB, and 127 GB. All but the 32 and 64 GB so-called
"barriers" are due to arithmetic limitations on how older BIOSs addresses
sectors or clusters on the HDDs. The 32 GB barrier is unique to Award BIOSs
with version numbers 4.5x and older than June 1999 where the computer may
hang at detection. The 64 GB barrier is an FDISK limitation.
See also
http://www.biosupgrade.co.uk/learn_bios_hdd1.htm
http://www.wimsbios.com/HTML1/faq.html#q15
http://www.storagereview.com/welcome.pl/http://www.storagereview.com/guide2000/ref/hdd/bios/sizeGB315.html
for good overviews.
There are some diagnostics utilities who can check for Int13 extensions for
supporting >8.4 GB drives--can't think of any DOS-based ones off the top,
but there certainly are some Windows-based ones.
Generally, I've yet to find a Pentium II-based system with an 8.4
GB-limited BIOS. If the BIOS isn't Award, and older then 6/1999, then the
next physical/arithmetic limit is 127 GB. Older machines will vary.
I'm not positive about the 14 GB limit...never seen that. Some drives have
"capacity clip" jumpers that limit the capacity to below a certain level,
like some IBM (now Hitachi) drives, though 14 is an odd value.
You probably know drive manufacturers make available utilities like
Ontrack, EZ-Drive, etc. to get around BIOS limitations for older
machines--these are microcode routines that get installed in the MBR
(Master Boot Record--first thing read when trying to boot off a HDD) of the
primary master HDD and load up into and over where normal BIOS routines for
HDD access reside. These are known as DDO (Disk Drive Overlay) programs,
because they "overlay" the legacy BIOS code with their own hard drive
access routines. Check the manufacturers' Web site or
http://www.ontrack.com/, for example, for more info.
>David J. Broderick
>djbroder@mit.edu
> Audio Visual Project Technician
> MIT AV 617 253 2808
> FAX 617 253 5945
> <http://web.mit.edu/djbroder/www>http://web.mit.edu/djbroder/www
Kerem
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Dave--<br><br>
At 03/04/24 15:12 Thursday, Dave Broderick wrote:<br>
<blockquote type=cite class=cite cite>I used to sort of know this.<br>
Back in the "old days" 486's had disk drive limits of 512MB.
Then, with Pentium I , there were 1,2,4 and 8 Gig limits, then, around
Pentium II time, practical limits started to go away. By Pentium III time
(perhaps before) you could pretty much install whatever you could by in a
store.<br><br>
Once in a while, I'm tempted to resurrect an older machine and install a
bigger hard drive. The "kudge test" is to put the newer drive
into machine. If the BIOS reports the correct values for the drive size,
I'm probably OK, if not I take it out. I had an old machine once, and i
put a 20gig drive into it. It reported a 14gig drive. "Well, what
the heck", I thought. Sure enough, files would mysteriously
disappear.<br><br>
Anyone know of a more scientific way to test a machine for disk
capacity?</blockquote><br>
There are 7 major disk capacity limitations: 504 MB, 2.0 GB (2,048 MB),
4.2 GB, 8.4 GB, 32 GB, 64 GB, and 127 GB. All but the 32 and 64 GB
so-called "barriers" are due to arithmetic limitations on how
older BIOSs addresses sectors or clusters on the HDDs. The 32 GB barrier
is unique to Award BIOSs with version numbers 4.5x and older than June
1999 where the computer may hang at detection. The 64 GB barrier is an
FDISK limitation.<br><br>
See also<br>
<a href="http://www.biosupgrade.co.uk/learn_bios_hdd1.htm" eudora="autourl">http://www.biosupgrade.co.uk/learn_bios_hdd1.htm</a><br>
<a href="http://www.wimsbios.com/HTML1/faq.html#q15" eudora="autourl">http://www.wimsbios.com/HTML1/faq.html#q15</a><br>
<a href="http://www.storagereview.com/welcome.pl/http://www.storagereview.com/guide2000/ref/hdd/bios/sizeGB315.html" eudora="autourl">http://www.storagereview.com/welcome.pl/http://www.storagereview.com/guide2000/ref/hdd/bios/sizeGB315.html</a><br><br>
for good overviews.<br><br>
There are some diagnostics utilities who can check for Int13 extensions
for supporting >8.4 GB drives--can't think of any DOS-based ones off
the top, but there certainly are some Windows-based ones.<br><br>
Generally, I've yet to find a Pentium II-based system with an 8.4
GB-limited BIOS. If the BIOS isn't Award, and older then 6/1999, then the
next physical/arithmetic limit is 127 GB. Older machines will
vary.<br><br>
I'm not positive about the 14 GB limit...never seen that. Some drives
have "capacity clip" jumpers that limit the capacity to below a
certain level, like some IBM (now Hitachi) drives, though 14 is an odd
value.<br><br>
You probably know drive manufacturers make available utilities like
Ontrack, EZ-Drive, etc. to get around BIOS limitations for older
machines--these are microcode routines that get installed in the MBR
(Master Boot Record--first thing read when trying to boot off a HDD) of
the primary master HDD and load up into and over where normal BIOS
routines for HDD access reside. These are known as DDO (Disk Drive
Overlay) programs, because they "overlay" the legacy BIOS code
with their own hard drive access routines. Check the manufacturers' Web
site or
<a href="http://www.ontrack.com/" eudora="autourl">http://www.ontrack.com/</a>,
for example, for more info.<br><br>
<blockquote type=cite class=cite cite>David J. Broderick <br>
<font color="#0000FF"><b>djbroder@mit.edu <br>
</b></font><x-tab> </x-tab>Audio
Visual Project Technician<br>
<x-tab> </x-tab>MIT AV 617
<b>253 2808 <br>
</b><x-tab> </x-tab>FAX
617 253 5945 <br>
<x-tab> </x-tab><a href="http://web.mit.edu/djbroder/www">http://web.mit.edu/djbroder/www</a>
</blockquote><br>
Kerem<br>
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