Author: Ricardo Gibert
Date: 20:40:36 09/07/03
Go up one level in this thread
On September 07, 2003 at 22:43:39, Robert Hyatt wrote: >On September 07, 2003 at 16:39:41, Bo Persson wrote: > >>On September 07, 2003 at 11:47:33, Robert Hyatt wrote: >> >>>On September 06, 2003 at 19:41:00, Gian-Carlo Pascutto wrote: >>> >>>>On September 06, 2003 at 19:31:40, Michael P. Nance Sr. wrote: >>>> >>>>>Let Me see if I understand this fully ,and ask the following questions? Isn't >WS 2003 scalable to 64 bit? >>>> >>>>The operating system itself may very well be, but you cannot get the 64 bit >>>>version for Opteron right now. >>>> >>>>>It should run both 32 and 64 bit Programs right? >>>> >>>>The normal version will not run 64 bit programs. >>> >>>How can it _Prevent_ 64 bit instructions? >>> >>>It can't... >> >>It can actually, beacuse of the extremely twisted instruction set. >> >>AMD has redefined some bit patterns so that they behave differently in 32 bit >>and 64 bit mode. To use 64 bit registers you need some size-override prefixes >>that have a different meaning in 32 bit mode. >> >>Just like we have 16 bit and 32 bit segments for the IA32, we need 64 bit >>segments for the Opteron. That seems to require OS support. >> >> >>Bo Persson > > >When I first looked at this stuff, it appeared to me to be the same issue >as that which ocurred with the YMP and then the C90 in the Cray series, >which introduced new stuff. A program could use the stuff without the O/S >knowing. IE the OS didn't understand that vector registers became twice as >long, but that didn't matter with a single application running by itself. I >can't imagine that it is not possible on the Opteron to finagle yourself into >a 64 bit world without the O/S knowing about it, but I could certainly be >wrong. I would be amazed and disappointed if your assumption is mistaken.
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