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Into the Core - Intel's New Core CPU
Tyler Too writes "Hannibal over at Ars Technica has an in-depth look at Intel's new Core processors. From the article: 'In a time when an increasing number of processors are moving away from out-of-order execution (OOOE, or sometimes just OOO) toward in-order, more VLIW-like designs that rely heavily on multithreading and compiler/coder smarts for their performance, Core is as full-throated an affirmation of the ongoing importance of OOOE as you can get.'"
As you fear a beating from the Intel side after what I say I fear I will receive a beating from both.
In my personal experience the AMD chips have been the fastest systems I have ever owned. My problem with them is the boards made for them (this is personal experience only) tend to become unstable after a couple of years. Intel boards, in my experience, stay stable longer.
For example, I have two 5 year old systems, one with a Gigabyte AMD Athlon board, and one with a true Intel P3 board. Both run Slackware. Both have insane cooling so the board temps never go over 100 degrees. The Athlon board system will occasionally reboot for no reason. The Intel board system has run for months without ever needing to be touched. The last time I brought it down was for a power outage that lasted longer than the battery on my UPS. I have tested everything on the Athlon system. The power supply is solid, the hard drive is new and the second one I have installed, none of the controllers test bad, and while it is running nothing tests bad using diagnostics. Then it suddenly reboots.
One would think this an isolated incident but I have build 6 Athlon systems in the last 5 years for friends and only two are still stable. All of the Intel systems I have built with true Intel boards in the last 15 years are still running including a 486 DX/2 66. I know this is personal experience only and not a good enough sample to make any real judgement but as for me, I pick Intel. That said, I believe the problems I have had with AMD come from the fact that none of the boards are made by AMD. If AMD made a board up to the same standards as its CPU I believe my opinion would change in a heartbeat.
You may commence my flogging now...
No animals were harmed in the making of this sig.
Well, there was that one puppy, but he is all better now.
Right, there are two camps for the "high-end" branch prediction concept:
Camp 1: devise adaptive, multi-component prediction systems that offer both fast and accurate branch prediction. Waste hardware purely for branch prediction.
Camp 2: Use the compiler hint if available, otherwise execute both paths, and throw away the incorrect processing path. It seems cheaper on the surface, but you have to realize: all that extra fetching to process both paths in reasonable time mean more fetch bandwidth and more execution units required just to keep up.
Obviously, if your code contains lots of branches that cannot be predicted by the compiler hints, the Camp 2 solution is going to perform worse. The advantage of active branch prediction is that you never have to recompile the code to keep the branch hints "optimized" if your datasets change.
It doesn't really matter which camp you choose, because both camps waste space on a Branch Target Buffer (predicts the TARGET of the branch) anyway, and that's often more costly than the branch direction predictor. Even the Itanium has a BTB, that's how it can instantly start executing the "branch taken" case.
The Itanium is just taking advantage of a serious architectural flaw to perform branch prediction. Even modern compilers are inserting 20% or more "noops" into the instruction stream, why not take advantage of that underutilization. On any other platform, it would be a very stupid approach to branch prediction.
Man is the animal that laughs.
And occasionally whores for Karma.