Los Alamos to Use AMD's Opteron in Linux Clusters

nuke-alwin writes "eWeek is reporting that Los Alamos National Laboratory announced it will use more than 3,300 Opteron chips in two of its Linux clusters. According to the article 'The key to Opteron, as it tries to gain traction not only against Intel Corp.'s 64-bit Itanium chip but also its 32-bit Xeon offerings, is its ability to run both 32-bit and 64-bit applications equally well.'"

Comments

The key

[mao che minh]

Not only can the Opteron power both 32-bit and 64-bit, but it also performs just as well as the Itanium in either environment. The Opteron is also far cheaper (especially when you compare the costs of 3,000 Opterons to 3,000 Itaniums, as most potential customers will).

Intel can't compete with the Opteron on merits alone. It will be interesting to see what they try next.

Errm...

[pr0ntab]

Yeah, and you also need to reboot your Pentiums to run 16-bit code.

It is just the state of a flag in a control register. In particular, see page 68 of
AMD's Opteron System Programming Guide.

64-bit mode is enabled with the flip of bit 8 of the EFER Model-Specific Register. Otherwise it defaults to 32-bit mode. OS designers should test/set this bit just before running a thread in the scheduler, or jumping into system code as it can only be modified by code running in ring 0. This is the same way people treated the Virtual-8086 (16-bit) mode bit in CR0. In fact, you can combine the protected-mode, virtual-8086 mode, and "long mode" bits to have a variety of register-size and memory addressing modes per thread.