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Which Processor Is Best For Real-Time Computations?
NoWhere Man asks: "For the longest time my friends and I have been arguing over which processor is better (Intel or AMD). I know this is an ongoing battle everywhere as well, but it took an interesting turn the other day. Which processor would be better for realtime, high end mathematical computations? AMD's Athlon? P3 Xeon? or Dual Processors? If anyone could recommend system specs, keeping it cost effective at the same time, it would help."
A couple of folks have alluded to this, but I'll reiterate in an attempt to make it clear; real time systems imply bounded response times. That does not directly imply a *faster* response time (altho the goal is to reduce the gauranteed bound on response times).
... if the computation by nature is unbounded, you wont get realtime performance out of any processor.
Hence, the phrase "real-time mathematical computations" is almost an oxymoron
Basically, I'm attempting to point out that "real time" and "fast" are not synonymous.
Excellent points; let me add a coupla more: I am not sure what 'real time mathematical computations' means here. CPUs that can crunch complex mathematical systems in real time, are usually developed by DARPA and cost millions per unit (I am referring to jet fighter avionics packages; usually TI or Rockwell chips).
Now, if the poster is referring to mathematical problems (but not 'real time', more like 'solved in a reasonable time'), the above post is right on the money: do not buy an SMP system --at least not an x86 SMP system (I don't have any exprience with Alphas). The problem with x86 SMPs is bus speeds, i.e. communication between CPUs on the same board. Using fast network interconnects (gigabit speeds) you can usually get better performance between boxes than between CPUs for some SMP systems (particularly quads and 8-ways). Duals are not as problematic, so for compactness' sake they might worth the $$$...
Keep in mind though, this is not the way things *should* be, it's just the state of the art --which sucks right now in x86-land. With better motherboards coming up (not to mention better SMP support by all the different OSes --the new Linux kernels seem to have solved context switching problems that were killing SMP machines, for example), eventually SMP machines will be the way to go...
engineers never lie; we just approximate the truth.
If you're doing mathematical computations, your best bet would be a CPU good with floating point. Your best bet would be an SMP Alpha. With a better floating point unit than Intel and AMD, and an outright faster CPU, you'd get a lot more done in less time. Only problem in this case is cost, since the average Alpha system, IIRC, costs more than most x86 systems. That might not be true, so do your research.
Which processor would be better for realtime, high end mathematical computations?
High end mathematical computations are unlikely to run in real time on any processor. Do you really mean games?
The AMD Athlon has a superior FPU at the same clock speed, which is useful for scientific applications. Check this page here for further details. (Notice on the same page that the Athlon is not better at everything though).
Are you referring to hard real-time applications? If so, you don't want an SMP system. Infact, you don't even want a system with a cache. Why? Because hard real-time applications optimize for worst case performance. Caches do well to improve average case performance, but usually hurt worst case performance. Thus, hard real time systems usually don't use caches.
In general, real time apps (even soft real time, like video or audio decode) are concerned more with low latency then high throughput. As a result, you aren't going to want an SMP system. The complex caching systems in SMP's is going to make performance even *less* predictable which is precisely *not* what you want for real-time.
If you just want a really fast media-cruncher, then you don't want to be running x86. If you're serious, you'll go for something like an Alpha, that will smoke any x86 in FPU. Besides, if you really want to get into real time media processing, you are going to need a great deal of bandwidth, and commodity x86 hardware isn't going to get you where you need to go.
If what you really want is a budget box to run games on, then get an Athlon. A quick review of any games site in existence will tell you that Athlons beat Intel's offering in every regard these days. There's no reason to bother Slashdot with such common questions. Any of the DIY gamer sites will have a host of articles with benchmarks running Quake or Unreal or whatever it is kids play these days.
I get the impression that this post is from someone who doesn't understand real time computation, and just through that phrase in there to make their question sound more sophisticated.
--Lenny
If you're doing Signal Processing or DSP-related tasks, the 7400 smokes. ;)
As always, it all depends on what numbers you're crunching, and for what purpose. The vector processing in the 7400 is pretty sweet if done right, and one of the Linux PPC variants has full support now.
Just a though to get away from x86
Pope
It doesn't mean much now, it's built for the future.
No, really, it is. What does real-time have to do with this? You can't solve an arbitrarily complex mathematical problem in a bounded amount of time. And that's what real-time is, bounded. Real-time has nothing to do with speed in the sense that this question is phrased. An example: A given problem must be solved in 15 seconds or less. Chip A can solve the problem in 1 second most of the time, but will take 30 seconds every once in a while. Chip B will usually take 5 seconds, but never more than 10. Guess which chip is can give you a real-time guarantee? That's right, even though Chip B is usually slower, it is the one you pick.