Originally posted by: Furen
Here's an old forum link:
http://www.xtremesystems.org/forums/showthread.php?t=59766&highlight=opteron
X86 secret (or whatever the website is called) did an article on this a long time ago so I'll paraphrase it a bit:
Basically whenever a program asks the bios if the cpu is HT capable it looks up this one bit at a certain address (which I dont care to look for right now). This does not mean that the A64s are SMT-capable, it just means that the cpu tricks programs into thinking it is. You ask why use "Hyperthreading"? AMD is not using hyperthreading at all. They use the same CPU ID bit because they want to take advantage of Intel's HT optimizations on mostly singlethreaded programs that dont support SMP, there's nothing on the CPU that has anything to do with HT except for that CPUID bit being 1 instead of a 0.