Slashdot Mirror
Dual Cores Taken for a Spin in Multitasking
Vigile writes "While dual cores are just now starting to hit the scene from processor vendors, PC Perspective has taken the first offering from Intel, the Extreme Edition 840, through the paces in single- and multi-tasking environments. It seems that those two cores can make quite a difference if you have as many applications open and working as the author does in the test." It's worth noting that each scenario consists of only desktop applications, and it'd still be interesting to see some common server benchmarks, such as a database or web server.
How long before applications start figuring that they should have an entire core dedicated to them?
Windows, for example. What if the next version of Windows requires a dual-core processor to be usable? You know..Windows gets one core to idle at 80% of its capacity..and spills over into the other core when loading a text file.
If things stayed the way they were now, and the entire other core could be kept separate from the OS and used for gaming/other applications, it would be a great idea.
But guess what.
Job? I don't have time to get a job! Who will sit around and bitch about being broke and unemployed then?
That is not necessarily true.
I know this article is talking about Intel dual core chips, but for well-designed CPUs with integrated memory controllers (Power5, Ultrasparc IV, Opteron), the difference between a single dual-core CPU and two single-core CPUs is significant.
On chips with built in memory controllers, as you increase the number of cores on a chip the memory bandwidth per core decreases, however as you increase the number of chips in a system, the memory bandwidth per core remains the same and the number of cores increases.
That can amount to a big performance difference when running memory-intensive jobs.
Intel seem to be really losing the plot here at the moment. In multichip configurations, Intel's memory bandwidth already sucks compared to Opteron. Multicore per chip is only going to make it FAR worse.
In general and assuming a non broken cache architecture, a 2CPU/core solution will feel faster than a single cpu solution with twice the cpu frequency.
The total number of cpy cycles are the same, but the average queue-length for a process waiting for the CPU is half, i.e. the latency before your process is scheduled is lower making it "feel" faster.
That highly depends on the problem. If your problem is highly parallizable and the application that resolves your problem has been written (correctly) in a multithreaded way, then two CPU's will perform better. (As you say, it doesn't scale in a linear way)
Of course, you might just say that a parallizable problem is not one problem, but many small problems that need to be solved separately ;-)
Ahhh...the great dumpster continuum. Many a free computer will be found there. -- sowth (748135)
Who the hell runs benchmarks with FireFox and iTunes.
if you ask me, the people that desperately need the ability to multitask are folks in the creative industry. Every 5 minutes bounce back and forth between massive applications rendering huge files.
Nothing sucks more then opening a 400dpi photoshop document and not having InDesign respond since your single core CPU is being bogarted.
SMP is probably the only reason I still find my crusty old Dual 450 g4 useful. It does things slowly, but it doesn't "feel" slow. If something is taking its sweet ass time, I can usually do something else without waiting years for windows and menus to draw.
"Things are more moderner than before- bigger, and yet smaller- it's computers-- San Dimas High School football RULES!"
Is it just me or did the performance of the single core AMD relative to the Intel dual core in those benchmarks just scream out..."I want the AMD dual core!"?
Seriously, unless you're application can run in the cache on the Intel parts, the AMD is gonna win hands down when running at the same clock rate which translates pretty closely to the same power consumption. AMD will yet be a tad lighter on power consumption just because the stuff is packed more tightly even though it has more active components. Equal 'wire' size + smaller size = shorter 'wires' resulting in reduced IR losses (for the same operating voltage).
I'll probably get flamed for this....
Increased performance in CPUs has normally come from faster clock rates and more complex circuitry. As we all know, Intel (and the others) have bailed out on faster clocks. If you add more complex circuitry, the logic delay increases--to keep the clock rate up, you have to burn power.
What does this mean? The old-fashioned ways of getting more performance are dead--if you try it, the chip will burn up. It's easier to build two 1X MIP cores than one 2X MIP core. Like it or not, dual cores are the only solution; with transistor scaling, we'll have to go to 4, 8, and 16 cores in the next few years. IBM went dual-core with the PowerPC in 2001. Intel, AMD, and Sun are just following suit.
Not bummed out yet? Massive parallelism works well for people doing scientific computing, but for the average joe, it's useless. I don't care how fast a processor is--I usually have one task that will crush it--but rarely do I have two time-critical things to worry about at the same time. In the article referenced, they had to work hard to find things that would test the dual-core features. Parallel computing and multiple cores sounds great. History buffs will know about Thinking Machines, Meiko, Kendell Square, MasPar, NCUBE, Sequent, Transputer, Parsytec, Cray, and so on.... Not a happy ending.
So.... we can't get more single processor performance without bursting into flames. And parallel machines are only useful to a small market. IMO, it's gonna get grim. (And before anyone says new paradigm of computing to take advantage of the parallel resource, put down the crack pipe and think about it--we've been waiting for that paradigm for about 40 years. Remember occam? I thought not.)
Except that this is a desktop processor, that won't be shipping in server systems. So in actual fact it's worth noting that the entire point is that each scenario consists of only desktop applications.
While that's true, these dual core chips (especially Intel's lame single-memory bus design) really seem targeted towards the desktop market where the impact is greatest, yet cost differential is realativly small (in relation to the total price of a system including software.)
I'm more interested in what IBM's Cell processor can do. While some problems are definately single threaded by nature, the majority are not. I have a GIS application that could definately benefit from as many processors as I can throw at it (although there comes a point where you need more memory, disk I/O etc. too so you still need to spread them out over a cluster to some degree.)
Even in a multi-memory controller system the same physical memory is shared, so there has to be some performance hit when running more than one cpu, so I doubt the actual memory bandwidth per chip will be the same. Or is there some architectural trick that removes that bottleneck in practice?