What it comes down to is this: so far, all the servers I've been administering have been 32-bit P3/P4/Athlon alikes, so if a server died and we needed it up NOW we could go to a local computer store here in smalltown USA, buy some desktop machine, swap harddrives, press enter a few times while kudzu does its thing, and have a working machine.
Now, we're moving to Opteron-based servers, and I just was wondering if it's reasonable to expect that, in a worst-case scenario, we could get an Athlon/64 system locally, and have it work, even if not optimally.
Obviously, the Opteron is better and faster, but if the Athlon 64 will run CentOS X86/64, then I can be pretty certain that in the worst case, I can run to the local Performance Leet g4m3rz store, and get an Athlon/64 to get a needed database server back online.
Just checking the accuracy of the data behind my decisions. (I've turned down Xeon servers for this reason)
-Ben
On Wednesday 28 December 2005 12:57, Bryan J. Smith wrote:
Benjamin Smith lists@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.h...
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@ieee.org http://thebs413.blogspot.com
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