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.
>Larry
>===============================================================================

>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.
(1024cylinders*16heads*63sectors/track*512bytes/sector=
528482304bytes1024bytes/KB=516096KB1024KB/MB=504MB)

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
upgrade;
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.

Larry
=======================================================================

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