Multi Core and Multi Threading : How work this stuff ?

[giuseppe]

I started about this in this topic
http://forums.alientrap.local/viewtopic.php?t=5483

I quote the posts here:

I know few things about hardware but i can remember you these few things...

Nexuiz dont support multicore CPU. So if u have for ex a p4 3.0Ghz, change that with a dual core 1.5Ghzx2 is the same to have a single core 1.5Ghz (bad for nexuiz if u want good graphic).
I know help a lot performance have more RAM and maybe change graphic card with a lot of ram dedicated.

Not true, a single core system have to run everything including nexuiz on that core. a multi core setup has more cores to spread the system load (such as the gpu driver load, which can be substantial, etc) on. thus multi core can well be better (and are in fact recommended for any current generation gpu too) then a mono core for Nexuiz. That said i dont know of any gaming capable mono core cpus sold today

Nexuiz dont support multicore: not true?
my example about running Nexuiz on dual 1.5Ghz instead a single core 3.0Ghz: not true?

Well my experience is that. I have now a dual 1.6Ghz instead my previous p4 3.2Ghz and nexuiz run with half or less frame rate and now if i want have a decent frame rate i have to set graphics to low value. But i can render with Blender 5% faster now for ex. Is true!
I have compared a single core and the 'equivalent' dual. I not said all dual core are bad for Nexuiz

Depends on what the current bottleneck of you system is giuseppe, however since nexuiz is not the only thing running on the system the other core/s of a multi core system is not idle. And thus more cores can still help performance even if nexuiz itself just uses the one thread. So no, 2x 1.5 ghz is not the same for nexuiz as 1x 1.5.

Oh, and comparing Mhz to Mhz across different cpu architectures is pointless these days

if your new 1.6 ghz (c2d i assume) is running nexuiz at half fps compared to a (p4?) of 3.2 ghz at otherwise comparable hardware, theres proly something wrong with your puter (and +5% blender render speed sounds to little too). The c2d (and just abt every other modern performance directed cpu architecture) get much more done per mhz then the p4 arc does.

from here

http://en.wikipedia.org/wiki/Dual-core

The amount of performance gained by the use of a multi-core processor is strongly dependent on the software algorithms and implementation.
...
In addition to operating system (OS) support, adjustments to existing software are required to maximize utilization of the computing resources provided by multi-core processors. Also, the ability of multi-core processors to increase application performance depends on the use of multiple threads within applications.
...
Two processing cores sharing the same system bus and memory bandwidth limits the real-world performance advantage.

So multi core tecnology is much better single core but needs appropriate 'software algorithms and implementation' that use 'multiple threads' and needs appropriate hw components.
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And from here
http://compreviews.about.com/od/cpus/a/dualcore.htm

Most of the early dual-core processors are going to be running at lower clock speeds compared to single core processors. The rational behind it is that a dual-core processor with each running at 1GHz should be equivalent to a single processor running at 2GBz. The problem is that this doesn't work in practice when the applications are not written to take advantage of the multiple processors. Until the software is written this way, unthreaded applications will run faster on a single processor than a dual-core CPU.

So a dual core 2.50-3.00 Ghz x 2 is good for nexuiz but my 1.50 Ghz x 2 i dont think (sure with a good graphic card with a lot of ram yes). The fact is Nexuiz cant take the great advantage of multi thread. And is a pity.
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Sorry k0jak im OT


[edit: i correct my info]
-my old CPU was a pentium HT 3.20Ghz, my new is a pentium dual 1.60 Ghz x2
-now i can have with blender render 50% faster (just controlled my old renders)

Hmm you either miss my point or ignore it anyways, lets stop threadjacking.

simply maybe i cant understand
i start a new topic to continue

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I want learn more about multi core tecnology and sw that support or not the multi threading.
Ty

[tZork]

Well nexuiz itself does not benefit from multi core since its single threaded. But on a computers theres always a pile of other things running (each in its own process and thread/s). In the the mono core scenario, all of these are running on the same cpu, obviously. So if, lets say your AV scanner, suddenly needs a big chunk of cpu time to do something and your playing nexuiz, nexuiz will get starved for cpu time. In a multi core setup the system can shuffle threads around to the to the least bzy cpu and keep everything running smoother. Also things like the gpu driver may use more then one core even if the game itself is single thread. So what the article fails to mention is that every modern system is made up of many processes, and because of this multi cores does help even single threaded applications by making more cpu time available. The gain is of course never higher then the full speed of one of these cores/cpus in the single threaded applications case.

If you had a case where you have one 3ghz mono core and one 1.5 ghz dual core _off precisely the same architecture_, the single core one would doubtlessly give you more nexuiz performance. but that scenario is unlikely to ever happen

Also in the case of nexuiz, its more gpu then cpu bound (unless your running a server or a local game).

[Silica Gel: Do Not Eat]

A modern dual core cpu is faster than an old p4 single core cpu even with one core tied behind its back.

Checkout the link to the benchmark comparisons

Notice the Cinebench r10 single threaded benchmark.



http://www.anandtech.com/bench/default.aspx?p=92&p2=54&i=2.3.4.5.6.25.26.27.28.29.30.31.32.33.34.35.36.37.38.39.40.41.42.43.44.45.46.47.48.49.50

[giuseppe]

If you had a case where you have one 3ghz mono core and one 1.5 ghz dual core _off precisely the same architecture_, the single core one would doubtlessly give you more nexuiz performance.

Is my case!
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@vomit
wait! but you compare a single core at 3.60Ghz with a dual core at 3.33Ghz (x2)? Its clear the second is the best anyway!

instead this is similar to my case
http://www.anandtech.com/bench/default.aspx?p=92&p2=69
(single core have +1Mb cache)

Intel Pentium 4 660 - 3.6GHz - 2MB L2
vs. Intel Pentium Dual Core E2160 - 1.80GHz - 1MB L2

Cinebench R10 - Single Threaded Benchmark
Score in CBMarks - Higher is Better
2245 - 1968

single core win (only +277 but win)

[Silica Gel: Do Not Eat]

The e2160 is about 2 years old and was a " low end cpu"
And its almost as fast with a single threaded app as a "High end" P4 with twice the clock speed!


Well I bet if you under-clocked a shiny new dual core to half the clock frequency of that of your p4 it would still be faster (Even on single threaded apps!) than your p4 and consume half the power and run much much cooler.

[Ed]

If we're talking about Nexuiz performance, let's not look at other benchmarks, look at Nexuiz:
http://global.phoronix-test-suite.com/? ... y&u=nexuiz

Must be some single core/SMP examples in there.

[Willis]

If you had a case where you have one 3ghz mono core and one 1.5 ghz dual core _off precisely the same architecture_, the single core one would doubtlessly give you more nexuiz performance.

Is my case!

This actually is not your case. You are comparing only by clock speed, and you can only do that when the two CPUs are of the same architecture (P4 vs P4 or Core 2 Duo vs Core 2 Duo).

When moving from P4 to Core 2 Duo, there is much more than just clock speed, but rather efficiency as well. The Core 2 Duo will blow the pants off of any P4 line period.

Also, as far as mutli-threading, DP (the game engine itself) doesn't benefit directly from multicore, in the fact that it doesn't offload physics or sound or anything like that, but your graphics card drivers will still benefit from it as they can run on a seperate core/thread themselves.

[Silica Gel: Do Not Eat]

Nexuiz dont support multicore: not true?
my example about running Nexuiz on dual 1.5Ghz instead a single core 3.0Ghz: not true?

Well my experience is that. I have now a dual 1.6Ghz instead my previous p4 3.2Ghz and nexuiz run with half or less frame rate and now if i want have a decent frame rate i have to set graphics to low value. But i can render with Blender 5% faster now for ex. Is true!
I have compared a single core and the 'equivalent' dual. I not said all dual core are bad for Nexuiz

I went from a P4 3.2 to an E2200 (2.2 X 2) and had noticed a modest improvemnt in nexuiz.
Sounds like your experience was not related to CPU itself. What OS did you use?

If i take a modern 3ghz dual core cpu and disable one core, it will still be faster and more efficient than a 3ghz P4.

Anyways gigahertz is a silly thing to compare CPUs by.

[giuseppe]

If we're talking about Nexuiz performance...

Not only. My request was:

I want learn more about multi core tecnology and sw that support or not the multi threading.
Ty

So the topic is not dedicated to Nexuiz performance!

My topic take origin by this:

Ok my pc is shocking, and every new version makes nexuiz harder for me to play, and I want to be able to play at a good level again.

but now this topic in my intention is general about how multy thread tecnology works.
Ty
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@vomit
this is my pc ( i know is old )
mainboard : Asus P5S-MX SE
CPU : Intel Pentium dual cpu E2140 1.60 Ghz
cache L1 : 64 Kb
cache L2 : 1 Mb
RAM : 2x512 Mb SDRAM
VGA : Ati Radeon X600/X550 series - 256 MB ram
HD : Maxtor 6L200M0 180 Gb
OS : Windows xp sp2
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After tZork and Willis posts i understand that...
about OS threads: 2 threads can be executed really at same time by a dual core; in a sinlge core this is not possible maybe is simulated in someway;
than in dual core im oriented to think the work can be done in half time (single core speed = speed one of cores in a dual);
Willis say there is more to consider than the only speed of cpu in multi core and so the performance can rise;
about the work of graphic cards the drivers can take benefit form multi core cpu, so a graphic application that doesnt support multi threading can take benefit indirectly by that;

but im confused a bit...
a heavy graphic application that doesnt support multi threading run on a core and im oriented to think that core is very busy;
so how OS threads can be executed? on the other core? on both the cores? How much the graphic card must be good to help in this case?

[Urmel]

I already had a core2duo CPU quite early and in the first days I had to assign Nexuiz to one of the two cores manually via task manager to get reasonable performance. This wasn't changed by a new Nexuiz release but some Windows or driver update, I don't remember exactly.

I'm not too much into CPU technologies or something, but I guess it's the OS and/or the chipset (drivers) that are able to handle the threads of even one process (application) on two or more cores.