🚀 go-pugleaf

[snip]


Ha ha ha. What else can I do but laugh.

OK, lets assume that you genuinely didn't understand what I said on 27 Jul @
0:16 when I said:

  Hmmm, I didn't say, rather didn't mean to say that the partition table was
  used *solely* in the determination of the Translation method used, but
  rather, a partition table *effected* how this translation was determined.

  A simple example of this is if you create a partition, say the first
  partition table entry, manually choosing CHS mode in the BIOS. Once
  created, change the BIOS to "Auto". Now what does the BIOS report ?

  Second senario. Continuing on from above, Change the BIOS to use "Large",
  now create a second partition table entry (might have to use a third party
  util to do this), then change the BIOS to "Auto" once again. What does it
  report this time ?

Better still, lets ignore you, Rod, and pretend that someone less
adversarial than you, asked me to explain how to test this, but didn't quite
understand the terse description above.

The only drive I have free at this time is a 1.2GB Seagate ST31270A, but
this should suffice for our purposes of testing wether a partition table
effects the translation mode chosen by BIOS, when the Hard disk mode setting
is set to "Auto". The system uses a Soltek SL-52B2 motherboard based on an
Intel 430VX chipset and has an Award 4.51PG BIOS. Rev S3, for those who may
also have this motherboard. Not a current system, but that's all that I have
available, and shouldn't matter too much.

First off, enter the BIOS setup, Standard CMOS setup, cursor to Primary
Master, set the TYPE to "Auto", cursor to the MODE column, set that to
"Auto" as well :

    HARD DISKS         TYPE   SIZE     CYLS HEAD PRECOMP LANDZ SECTOR  MODE 
    ------------------------------------------------------------------------
    Primary Master   : Auto      0        0    0       0     0      0  AUTO

Save exit. Boot up on a floppy disk, mine being created from a Win95B
system, containing FDISK, FORMAT, etc. Same thing using Win9x Rescue disk.
See here for more details on my disk:
http://microdek.homepage.com/info/OSR2bootDiskette.htm#mydisk

Now pause on the BIOS report screen, the Boxed information that is displayed
upon completion of POST (Power On Self Tests), and before an OS begins to
load. It looks something like: 

+------------------------------------------------------------------------
| CPU Type          : IDT WinChip C6       Base Memory       :     640KB 
| Co-Processor      : Installed            Extended Memory   :   64512KB 
| CPU Clock         : 200MHz               Cache Memory      :     256KB 
+------------------------------------------------------------------------
| Diskette Drive  A : 1.44M, 3.5 in.       Display Type      : EGA/VGA 
| Diskette Drive  B : 1.44M, 3.5 in.       Serial Port(s)    : 3F8 2E8
| Pri. Master  Disk : LBA ,Mode 4, 1282MB  Parallel Port(s)  : 378

          blah, blah.... 

Booting from a floppy, you should have plenty of time to press the
Shift-Pause keystroke to Pause the system Bootstrap, and view this report.
Press a key to continue, afterwards.

Now wipe all entries from the partition table (using FDISK or a zeroing
util), then reboot. Do I really need to go into this detail ?  Perhaps, if
you don't know how to do this, then you shouldn't be proceeding. 

Anyway, without a partition table, the BIOS should choose LBA translation,
as shown in the above BIOS report. This much has never been disputed (by
me). 

Now, reboot, and change the Primary Master MODE to "Normal":

    HARD DISKS         TYPE   SIZE     CYLS HEAD PRECOMP LANDZ SECTOR  MODE 
    ------------------------------------------------------------------------
    Primary Master   : Auto      0        0    0       0     0      0 NORMAL

Save exit. The BIOS now reports CHS addressing:

 Pri. Master  Disk : CHS ,Mode 4, 1282MB 

Boot up on the floppy, and create a Primary DOS Partition. Choose defaults.
If you chose to use large disk support at the start of FDISK, then a FAT32x
(ID 0xC) partition is created, else a FAT16x (ID 0xE) partition is created.
If you were booting an earlier version of DOS, say DOS 6.22, then you won't
have access to the FAT16x, FAT32 or FAT32x, thus will be limited to creating
a maximum of ~500MB FAT16 (ID 0x6) partition. Reboot.

You can FORMAT it now, but it's not necessary for this experiment.

Change the Primary Master MODE to back to "Auto", Save and exit. The BIOS
still reports CHS mode. Why ?

Delete the partition, reboot, the BIOS now reports LBA. Hmm, so if the Auto
Hard disk mode setting was not influenced by a partition table, why did this
happen ?


Now try this. Change back to "Normal" mode, and then create a primary, but
at a capacity such that it will have more than 1024 Cyls, in my case, half
capacity 611MB looks fine, set the active partition to 1, change the Mode to
"LBA" or "Large", now try and create an extended partition.

Whoops, FDISK is saying that we have a 611MB partition, but the Total Disk
space if 504MB. Strange. OK, so delete and recreate the primary partition.
Reboot. Oh, look, the BIOS is reporting LRG, 1053MB. What happened to the
other 229MB ?

OK, lets see if I can create the extended partition now. Oh good, you can.
But, we are still missing 229MB. Something seriously screwy here. Change the
mode back to "Auto". It comes up as LBA, but still only 1053MB. 

Delete all partitions, reboot, now try. All is fine again.

In summary, a partition table with signature and reasonably accurate
entries, however they got there, will influence both the translation used
(LBA, Normal, Large), and in some cases, the capacity of a drive. Sure, what
I've described above shouldn't happen as an every day occurance, but that is
not the point.

Would someone like to try this with other BIOSes such as AMI, Phoenix, or
MrBIOS, and later versions of Award ?

If you want to investigate further, then you can use utilities like WDTBLCHK
(ftp://ftp.wdc.com/drivers/hdutil/tablechk.exe), from which you can extract
this type of info:

MODEL:                 ST31270A
CYLINDERS:                 2485
HEADS:                       16
SPT:                         63
PHY. SECTORS:           2505528
PHY. SIZE (MB):            1283

HD mode  INT 13h, 8         INT 13h, 41/48                     Xlat Info 
------- -----------------  --------------------------------- ------------
Large 	 621 64 63 1281MB    621 64 63 2503872 sect (1282MB) CHS to CHS 
LBA 	 621 64 63 1281MB    621 64 63 2503872 sect (1282MB) LBA 
Normal 	1024 16 63  528MB   2485 16 63 2504880 sect (1282MB) No Xlat 
		 	


I leave it as an exercise for the reader, to examine the differences between
the various partition table entries, so as to be able to manually edit it
with a disk editor like Nortons DISKEDIT. Tinker away, and you tell me...  

:)

  __   __  ________________________________________________________
 //)) //))| Richard RUDEK. MicroDek. Chatswood, Sydney. Australia. |
//\\ //\\ |http://microdek.homepage.com/                           |
          |________________________________________________________|