DOS disk size limit ~= 500Mb?
Walter Briscoe
528Mb. I have a 2Gb drive which is seen as such by my BIOS. (Type=47
Ncyl=4095 Nhead=16 Nsect=63). fdisk sees it as 504Mb. On the original
machine I had it in, fdisk sees it as 2Gb. If I fdisk it on the 2Gb
machine and format it on the other, I think I am deceiving myself as
cluster addresses > 16k seem to be inaccessible. I would appreciate an
explanation of this inconsistency and a pointer to a workround or a
reason why I am stuck with the situation
--
Walter Briscoe
Paul Schlyter
Walter Briscoe <wal...@wbriscoe.demon.co.uk> wrote:
> I have some vague memory about DOS drives being limited at one time to
> 528Mb.
Early IDE disk controllers were limited to a disk size of 504 MBytes.
> I have a 2Gb drive which is seen as such by my BIOS. (Type=47
> Ncyl=4095 Nhead=16 Nsect=63). fdisk sees it as 504Mb. On the original
> machine I had it in, fdisk sees it as 2Gb. If I fdisk it on the 2Gb
> machine and format it on the other, I think I am deceiving myself as
> cluster addresses > 16k seem to be inaccessible. I would appreciate an
> explanation of this inconsistency and a pointer to a workround or a
> reason why I am stuck with the situation
Try to set the number of cylinders to 1023 and the number of heads to
64. This requires that you don't have an older IDE disk controller
-- if you do, you're stuck with the size limit of the accessible disk
of 504 MBytes, unless you upgrade to an EIDE disk controller -- but
then you probably need to upgrade your ROM BIOS as well...
On the other hand, if you do have an EIDE disk controller, why not
try to let it auto-.detect your disk parameters?
--
----------------------------------------------------------------
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
Grev Turegatan 40, S-114 38 Stockholm, SWEDEN
e-mail: pau...@saaf.se paul.s...@ausys.se pa...@inorbit.com
WWW: New URL at http://193.12.249.96/pausch -- updated daily!
Jim Brown
Paul Schlyter wrote:
jb wrote:
older 486's tend to be limited to a maximum sector count of 1023 whcih
indeed corresponds to a max storage space of 503 MB. I have also run into
pentiums that had a bios limit of 4095 sectors which corresponds to max
accessable disk size of 2.1GB.
solution?
use a sector translation program such as on track's disk manager, or max
tor's max blast,
available by down load from either maxtor's or seagate's websites, as well
as others.
hardware translation was also available on some drive controllers.
These sector translation managers act to fool the system's bios by
logically reducing the number of sectors by increasing the number of tracks.
The upside is you can put large drives on your system.
The downside of these are that in order to load the operating system during
boot up, the sector translation software software must be loaded first --
and to do this, requires that the boot sector be altered to point to load
the sector translation driver first, instead of the boot routine -- exactly
the sort of thing that a boot sector virus might do.
I have found that some virus protection software does in fact detect the
altered boot sector and the manager, and thinking it is a virus, will
cheerfully _fix_ it for you .. which then renders the sector trans software
inoperative and your hard drive in accessible until the manager is reloaded
- and in the event of partition loss, can result in the necessity of
completely reloading your hard drive in order to get acccess to boot your
system.
It is for these reasons that my primary system drive is always run in a
native mode, that is, I always run a smaller drive as the primary system
drive which is less than or equal to whatever the natural sector limit
is.(1023 sectors/503mb) The large drives will be the secondary drrive. Doing
this will assure that the system will boot to the natively addressed drive
whether or not the sector translation software is operative.
I _NEVER_ well, almost never, run a large primary system drive. You can
store all your programs, data, etc on your large secondary drive, addressed
by the sector translation software, partitioned however you like.
If by chance the sector translation software is wiped out... your system
will still boot - and you can then fix the boot sector and regain access to
your secondary drive, hopefully with a minimum of pain and effort.
hope this helps.
John S. Fine
>
> I have some vague memory about DOS drives being limited at one time to
> Ncyl=4095 Nhead=16 Nsect=63). fdisk sees it as 504Mb. On the original
> machine I had it in, fdisk sees it as 2Gb.
The interface between DOS and the BIOS is limited to 1023 cylinders.
The interface between the BIOS and the drive is not limited to
1023 cylinders.
The interface between the BIOS and the drive is limited to 16
heads. The interface between DOS and the BIOS is not limited to
16 heads.
If you have 63 SPT and take both of the above limits then
DOS is limited to 504Mb. The usual solution is a smart BIOS
that splits the two limits apart:
The bios may talk to DOS pretending there are 64 heads and
1023 cylinders. The bios translates so that it talks to
the drive using 16 heads and 4092 cylinders. Most modern
bios's can do that (or something with the same effect).
Usually there is a setup option that you must turn on.
If you change the mapping that DOS sees then the
partition table will be invalid and you need to repartition
(losing all your data).
--
http://www.erols.com/johnfine/
http://www.geocities.com/SiliconValley/Peaks/8600/
ser...@my-dejanews.com
Walter Briscoe <wal...@wbriscoe.demon.co.uk> wrote:
> I have some vague memory about DOS drives being limited at one time to
> 528Mb. I have a 2Gb drive which is seen as such by my BIOS. (Type=47
> Ncyl=4095 Nhead=16 Nsect=63). fdisk sees it as 504Mb. On the original
> machine and format it on the other, I think I am deceiving myself as
> cluster addresses > 16k seem to be inaccessible. I would appreciate an
> explanation of this inconsistency and a pointer to a workround or a
Your BIOS doesnt support EIDE. If you dont want replace BIOS, try to install
DM (Disk Manager) with option "EIDE support driver".
> --
> Walter Briscoe
>
WBR,
Sergey
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own