[Soekris] comBIOS ver. 1.33 sees wrong disk size

der Mouse mouse at Rodents-Montreal.ORG
Tue Jul 5 14:49:35 UTC 2011

> Is there a bug / mis-feature of the BIOS that prevents it from sizing
> large drives correctly?  Does comBIOS v1.33 have a problem booting a
> kernel from a large partition?

> 	SanDisk Extreme III CF card 16 GB
> 	OWC Mercury Extreme Pro SSD 240 GB

> When the Soekris net5501-70 powers on, the net5501 displays on the console port:

> 	Pri Mas  SanDisk SDCFX3-16384                LBA Xlt 1024--63  16007 Mbyte
> 	Pri Sla  OWC Mercury Extreme Pro SSD     LBA Xlt 1024-255-63  134 Gbyte

> The size of the CF looks reasonably correct, however the SSD is well
> short of 240 GB.

It's probably 128G, being mis-printed in a strange cross between
disk-manufacturer (metric) gigabytes and real gigabytes.  128G is 137
metric gigs, but it's 134 million K.  I suspect the Gbyte there is
1000*1000*1024, which would make it a botch on the same order as
"1.44MB" floppies (which are 1.44*1000*1024 bytes).

> When the Debian installer starts to partition the disks, it reports
> the correct size:

>          SCSI1 (0,0,0) (sda) - 16.4 GB ATA SanDisk SDCFX3-1
>          SCSI1 (0,1,0) (sdb) - 240.1 GB ATA OWC Mercury Extr

I note 16.4 versus 16007; this reinforces my theory - 16007*1000*1024
is 16391.168, which would reasonably round off to 16.4 thousand.
(Depressing that Debian has bought into disk manufcaturers' attempts to
redefine the gigabyte...though the comBIOS's apparent schizoid cross
between the two is admittedly worse.)

There's some kind of boundary at 128G; presumably the comBIOS version
you've got isn't capable of passing it.  (I can't explain it, because I
don't know the underlying protocols enough.  I assume there's a 28-bit
block number field somewhere or some such, but that's just guessing.)

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