FDISK, cyl>1024, Disk Manager

FDISK, cyl>1024, Disk Manager

Post by Larry LeBla » Wed, 22 Nov 1995 04:00:00

Hello all,

I am posting in order to summarize the results of a post made by
myself last August.

I would also like to thank everyone who provided me with the findings
necessary for this post.

Original post:

>Hello FDISK gurus,
>Most of the postings I have read recently state that an IDE HD who's geometry
>is 1024*16*63, should equate to 540MB of secondary storage.  Based on my
>calculations (1024*16*63*512bytesPerSector/1024bytesPerK/1024KPerMeg), one
>should expect exactly 504MB!  This can't be one of those 1024bytes*1024Kbytes
>stories because 504MB=528,482,304bytes.  In which case, I understand why one
>would incorrectly state that it gives 528MB.  But why 540MB???
>Q1: Once and for all, what is the lowdown?
>I have 2 Conner CF1275A hard drives (1,275GB).  Thus far, because my system's
>BIOS does not support Logical Block Addressing (LBA), I have had to used Disk
>Manager for Conner drives in order to create large partitions.  This has
>caused me a good deal of grief when I tried to install the Linux OS on a
>second partition of the second drive.  The configuration prior to installation
>was as follows:
>DiskA, partition 1 - DOS - 1,275GB
>DiskB, partition 1 - DOS - 840MB (leaving the rest for Linux)
>Linux's version of FDISK reported that ALL of DiskB was already partitioned.  
>I was forced to use my ENTIRE second drive in order to complete the Linux
>installation.  I suspect that the incompatibility lies between Linux's FDISK
>and Disk Manager, which leads me to Q2.
>Q2: Can I simply replace my BIOS chip with a latter one that does support LBA
>and drop Disk Manager altogether?  If so, would I then be able to partition
>the drive into logical drives > 504MB with DOS' FDISK alone?  How exactly does
>this work?  The folks at American Megatrends say that I could not simply
>replace the chip!  A friend of mine says that he did just that for his system!
>Please reply via e-mail.

>Montreal, Quebec  CANADA
>"If you can keep your head while those about you are losing theirs,
>consider an exciting career as a guillotine operator!" R.Kipling

In replacing my motherboard with one who's BIOS support LBA, my
problem has been completely resolved.  My new configuration is as
follows (all managed by the LInux LOader):

DiskA, partition 1 - DOS - 1.275GB
DiskB, partition 1 - Linux swap space - 16MB
DiskB, partition 2 - Linux File System - 512MB
DiskB, partition 3 - Windows '95 - 777MB

Here are the facts (as I understand them):

A. My calculations were in fact correct.

B. Versions of OnTrack Disk Manager prior to 7.0 are not compatible
with Linux.  If you have a special version of Disk Manager for a drive
from a specific manufacturer (eg. Disk Manager for Conner drives), you
should have no trouble registering the product with OnTrack and then
upgrading to version 7.0.  The cost is of $25US and the upgrade can be
obtained by calling calling OnTrack at 1-800-752-1333 (612-937-1107).

C. A BIOS chip is very closely tied to a specific motherboard.  You
should first try to obtain a replacement from the motherboard vendor.
If you have a fairly common motherboard, you might try calling a BIOS
upgrade vendor found in various trade magazines (eg. Computer
Shopper).  One suggestion received suggested that I call TTI
(1-800-541-1943) and ask fro MR.BIOS.  Please note that this option is
not always possible.  My motherboard is a no-name clone from China so
I was SOL.

D. Due to DOS' limited FAT entry size (16 bits), someone had concerns
regarding the size of the partitions to be used by MS-DOS.  The
cluster overhang can become quite significant on large partitions with
generally small files.  Please consult the following chart for
resulting cluster sizes (where x is the partition size):

x < 128MB            2KB
128MB < x < 256MB 4KB
256MB < x < 512MB 8KB
512MB < x < 1024MB        16KB
1024MB < x < 2048MB       32KB
2048MB < x           64KB

Possible solutions:
1. If you have a flash BIOS, simply obtain the most recent version
(which is likely to have the required extension) and perform the
2. Obtain a BIOS upgrade from the motherboard manufacturer or from a
BIOS upgrade vendor;
3. Upgrade your version of Disk Manager;
4. Replace the motherboard with one that supports Logical Block
Addressing (LBA) (this is what I did 486DX2/66->486DX4/100);
5. Purchase an hard drive controller that has an onboard BIOS
extension that supports the features sought (eg. LBA).  Apparently,
you do pay a price in lost UMBs going this route;
6. I heard that you could obtain an expansion card that has the
required BIOS extentions.

Once again, many thanks for those involved.


Montreal, Quebec  CANADA
Murphy's Eleventh Law:
It is impossible to make anything foolproof, because fools are so ingenious.