A7N8X-E Deluxe and 160GB IDE disk

[Rainer Latka]

I have replaced the (defunct) EPOX mainboard of my PC by an ASUS A7N8X-E
Deluxe and now I'm observing some strange BIOS behaviour regarding an
160GB IDE disk: while the BIOS shows the total capacity correctly, the
cyl/hd/sec figures shown by the BIOS dont multiply to 160GB but to
cyl hd sec capacity
LBA 65535 16 255 136899993600
large 16643 255 63 136893335040
CHS 4095 240 255 128314368000

The mobo came with BIOS revision 1013, which is also the newest I could
find on the ASUS homepage

The disk holds several partitions that add up to 160GB and both Windows
XP and Linux seem to work perfectly well, so they obviously ignore the
erroneous BIOS data.

I wonder whether there may be some situations where this may
nevertheless lead to problems?

Any hints / warnings / experiences with this? I have not been able to
find anything about this in the newsgroup archives.

Rainer

 

[Robert Hancock]

I have replaced the (defunct) EPOX mainboard of my PC by an ASUS A7N8X-E
Deluxe and now I'm observing some strange BIOS behaviour regarding an
160GB IDE disk: while the BIOS shows the total capacity correctly, the
cyl/hd/sec figures shown by the BIOS dont multiply to 160GB but to
cyl hd sec capacity
LBA 65535 16 255 136899993600
large 16643 255 63 136893335040
CHS 4095 240 255 128314368000

CHS values cannot be used for devices over 128GB, the values reported
will always be 65535/16/255 which is sort of a dummy placeholder value.
The OS must use LBA calls which provide a linear sector number to access
the disk properly.

 

[Rainer Latka]

Robert Hancock schrieb am Samstag, 2. Juli 2005 05:32:

CHS values cannot be used for devices over 128GB, the values reported
will always be 65535/16/255 which is sort of a dummy placeholder
value. The OS must use LBA calls which provide a linear sector number
to access the disk properly.

yes I'm aware of the CHS limitation, but as you can see from the table
above, the BIOS reports wrong numbers also for the LBA and "large"
settings. So, where from do the installed Win XP and Linux operating
systems get the correct data (which they obviously do know)? And, is it
save to assume that all software will ignore the erroneous BIOS's LBA
figures?

 

[Robert Hancock]

yes I'm aware of the CHS limitation, but as you can see from the table
above, the BIOS reports wrong numbers also for the LBA and "large"
settings. So, where from do the installed Win XP and Linux operating
systems get the correct data (which they obviously do know)? And, is it
save to assume that all software will ignore the erroneous BIOS's LBA
figures?

The CHS values from the BIOS are ignored and the disk's LBA capacity is
used directly. LBA simply specifies a sector number from 0 to whatever,
it doesn't specify cylinder-head-sector.

 

[Rainer Latka]

Robert Hancock schrieb am Sonntag, 3. Juli 2005 10:40:

The CHS values from the BIOS are ignored and the disk's LBA capacity
is used directly. LBA simply specifies a sector number from 0 to
whatever, it doesn't specify cylinder-head-sector.

ok, thanks, so this seems to be safe.

Rainer