Quote Originally Posted by Drwho? View Post
Well, you assume that I am incorrect, I know you are ... I did put the stuff on the table, I told you, I tried a permutation of codes to figure out how large the decoding capability, and i ended up with 2 IPC per thread
... sorry ... If you had a part, you would end up with the same number , you can throw at me as much Powerpoint persentations as you can, you are not going to change my mind.
Fine, if you say so, I believe you. However your "5 decoders" information was wrong. Furthermore you did ignore my question why intel should be better. There are also only 4 decoders for 2 threads if SMT is activated.
Wrong information + ignoring -> lower trust -> less credibility.

you are free to trust your powerpoint presentation, I don't mind, you are just a little bit too quick to say that somebody is wrong, without even a part in your hands ... don't you think it is a little too much?
I didnt say that you are wrong in the IPC case, I just said that you are wrong with your decoder counting. Furthermore, the little picture that you nicely promoted to a whole "powerpoint presentation" was published in IEEE Micro March/April 2011. Of course it also came with an additional text:
Each block indicates a local pipeline that
forms a different thread switch domain.
Once a thread switch decision has b ee n
made at the start of the local pipeline, the de-
cision propagat es the pipeline’s length. A
thread switch can occur as o ften as every
cycle, so multiple threads c an be in flight
in the pipelines, but never in the same pipe-
stage. Decoupling queues, which exist for the
normal pipelining of the front-end, serve as
the different domains’ boundaries. Concep-
tually, the FPU c oprocessor’s front end is
an extension of the dispatch thread domain.
Now I believe you, but also I believe the authors of that paper (Michael Butler,Leslie Barnes,Debjit Das Sarma, Bob Gelinas). These people should at least know what they build. Thus my conclusion is:
There is a bug, or the less likely cases: They lied or your measurements were insufficient.

PS: Yeap, you can design code to figure out the specs of a CPU, it is a nice practice, you should try.
Yes, nothing new. But thanks for stating it for the other readers ;-)

regards

Opteron