Author: Robert Hyatt
Date: 08:36:36 09/25/03
Go up one level in this thread
On September 24, 2003 at 21:44:36, Jeremiah Penery wrote: >On September 24, 2003 at 20:01:10, Robert Hyatt wrote: > >>On September 24, 2003 at 18:41:59, Jeremiah Penery wrote: >> >>>On September 24, 2003 at 12:01:01, Robert Hyatt wrote: >>> >>>>On September 23, 2003 at 18:23:20, Jeremiah Penery wrote: >>>> >>>>>On September 23, 2003 at 17:27:48, Slater Wold wrote: >>>>> >>>>>>As soon as they have a 64-bit Opteron compiler (publicly available), I'll let >>>>>>you know. ;) >>>>> >>>>>GCC already does. >>>> >>>> >>>>You also need a 64 bit operating system, >>> >>>SuSE Linux has had an x86-64 version for a while. I guess there are a couple of >>>other now too. >>> >>> or else some assembly hacking. And >>>>then you have to get the compiler to produce a 64 bit code that will run on >>>>the 32 bit O/S. >>> >>>Huh? >> >> >>The opteron is an odd bird. If it isn't initialized to 64 bit mode, you can't >>get to the extra 64 bit registers. A user mode program can't do that easily, >>although I am sure it is possible with access to kernel mode and some inline >>assembly. > >From what I understand, it is not at all possible unless the OS is 64-bit. If >the CPU is booted in 32-bit mode, it is impossible to then run anything in >64-bit mode. 32 vs 64 bit is not a hardware switch, it is a bit in a register. I don't see why I couldn't get into kernel mode, and then set the bit myself, which is what the operating system has to do when it decides to run in 64 bit mode. I might have to do some ugly things like disable interrupts while in 64 bit mode so that I can occasionally swap back to 32 bit mode and allow interrupts, but I'd suspect it is doable. As I said also, with a lot of kludges.
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