AMD's CTO says Intel messed up

TalkBack 9 of 13:

Next »

« Previous

• Thread View
• Flat View

IA64 is as good as those applications which have ILP

available to be easily picked up by the compiler. The EPIC is an "interesting" design space point. I agree that in its initial instantiations it looks more like an expensive academic class project.

The motivation behind EPIC (and VLIW) is to have an ISA that makes it "easy" to express ILP and leverage unutilized functional units from witin the same instruction stream. This has a few basic flaws:

1) Compilers needs to discover and ensure that
the ILP is free of dependencies and thus can execute concurrently. It is well known that the compiler can only discover the "easy" parallelism and cannot do much about the more common dynamic dependencies.

2) The supescalar, dynamically scheduled pipelines are great at doing the dependency checking at run time thus enabling execution of ILP with dynamic dependencies. Itanium-2 is stuck at the VLIW scheme of things and thus cannot do this easily.

3) Interrupts, which are extremely frequent in server class of workloads (and nowdays server workload can be found to varying degrees and increasingly in "dektop" machines too) are extremely disraptive to the efficient operation of the pipelines, especially of the EPIC type.


Overall, Itanium-2 has several flaws but it is a good match for computation intensive tasks with few interrupts and thread switching. Intel could improve it by relaxing the EPIC/VLIW model a bit to allow for some SMT/CMT.

It is not clear to me that Intel will invest the billions in necessary R/D to make these improvements.

Posted by: Dr-T   Posted on: 09/25/06 You are currently: a Guest | Members login | Terms of Use

Alert moderator to an offensive message

Subscribe to this discussion via Email or RSS

SponsoredWhite Papers, Webcasts, and Downloads

• INNOV8 2.0: A Business Process Management Simulator IBM Innovate your business' process model, play against the market, compete ... Download Now
• Why Isn't Server Virtualization Saving Us More? A Few Small Changes May Dramatically Increase Your Efficiency VMware Companies have rapidly adopted server virtualization over the past few ... Download Now
• Three Steps You Need to Know to Stop Data Loss Varonis Sensitive data exposed to misuse or loss... it is the stuff of nightmares ... Download Now