[CentOS] Opteron, Athlon/64, and disaster recovery

Wed Dec 28 20:57:47 UTC 2005
Bryan J. Smith <thebs413 at earthlink.net>

Benjamin Smith <lists at benjamindsmith.com> wrote:
> Has anybody here taken a HDD configured with an Opteron
> system, and then put it into an Athlon/64 and had it work? 
> Are they interchangeable, like an Athlon/32 and a P3/P4? 

Yes, to a point.
An x86 system will _not_ boot a x86-64 kernel.
But yes, a x86-64 system _will_ boot a x86 kernel.

The x86-64 kernel puts the CPU into a 52-bit PAE memory mode.
x86 systems only support a 36-bit PAE memory mode.
For more, see my blog entry here:  
 
http://thebs413.blogspot.com/2005/10/what-is-x86-64-long-mode-memory-model.html
 

The only other issues are boot-time storage support.  Most
[parallel] ATA devices are no issue, because they are in the
stock ATA/IDE kernel support.  SATA is a different issue,
because many SATA drivers are SCSI block drivers at this
point, so they need to be built into the initrd (initial root
disk).

Linux isn't like NT 5.x (2000/XP/2003), which sets boot-time
information in the registry and will blue screen if you
change mainboard/chipsets.  Yes, not even changing the
ntbootdd.sys file for the appropriate ATA/SCSI works (like it
did for NT 4.0 and earlier).  The only way to change that is
to boot up another OS (e.g., Linux) with a registry editor
and manually change the 3 or so keys for the boot-time
storage device.

-- 
Bryan J. Smith     Professional, Technical Annoyance                      b.j.smith at ieee.org      http://thebs413.blogspot.com
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*** Speed doesn't kill, difference in speed does ***