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 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 > ---------------------------------------------------- > *** Speed doesn't kill, difference in speed does *** > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > -- "The best way to predict the future is to invent it." - XEROX PARC slogan, circa 1978