Re: PII vs PIII

From: w_tom (w_tom1_at_hotmail.com)
Date: 10/14/03 

Date: Tue, 14 Oct 2003 15:00:40 -0400

  SIOL - I was probably building computer systems (at
component level with soldering iron) before you were even
born. Apparently you don't even understand the priority
system of task execution. High priority task gets processed
immediately at the expense of a compiler program. And no
processor puts up a "do not disturb" sign. Task is only
executed, at most, for a prescribed amount of time - and then
another task is taken up. Or current task is immediately
interrupted to perform a higher priority task. No task can
"camp out" on a microprocessor as in SIOL's Point #2. There
is even this little thing called time slicing. Also nowhere
was mention of "random choice". Where out of the blue did
"random choice" come from?

  Because you don't fully understand how a preemptive
multitasking OS works, then you think a dual processor system
should be more responsive. If multiprocessor systems worked
as you described, then yes, the multiprocessor system would be
more responsive. But preemptive MT does not work as
described. Processors are constantly taking up new tasks even
when the current task is not completed. High priority or real
time tasks - that make for system interface responsiveness -
are processed immediately. Difference: a faster processor
means that real time task will be picked up and completed
quicker - which is why a 600 Mhz processor will finish
processing a real time task faster than two 300 Mhz
processors. It is why that 600 Mhz machine can be more
responsive.

  But again, this is speculation. You have not provided
numbers for your claims AND not even provided a research
study. Therein lies the problem. Whether dual processor
system is more or less responsive is irrelevant. You have
again only provided speculative theories; some not even based
in how preemptive MT works. Then you claim those speculative
theories prove your personal, subjective, observation. You
have only an opinion which you misrepresent as scientific
fact. It is what we call junk science reasoning.

  I am not saying the single high speed CPU is more or less
responsive than slower, multiprocessor system. I am saying
you do not have numbers or even a study to make your claims.
Even worse, because you could not support your claims with
numbers, then you posted insults at Lane Lewis, et al.
Personal insults is a symptom of junk science reasoning.

 Your only proof is your emotional opinion of how you 'feel'
the dual processor system works. And you did not even
demonstrate that both single and dual processor systems are
equivalently designed - have same memory capacity - same bus
speeds - same video subsystem. Just more reasons why what you
'felt' is actually nothing more than speculation.

  BTW, experience with current technology preemptive
multitasking OSes would indicate that 486 CPU cannot run XP.
IOW understanding how preemptive MT OSes works was not
demonstrated, AND experience is lacking. SIOL is also not
familiar with hardware required for an XP system. That again
is my point. Insufficient background (and numbers) to make
those claims. Conclusions are based on junk science
reasoning. Reasoning only good enough to express a personal
opinion - a relationship unique to that one person's machines.

SIOL wrote:
> "w_tom" <w_tom1@hotmail.com> wrote in message
> news:3F8B530B.DA41B79A@hotmail.com...
>> Steve Wolfe and SIOL simply speculate why a dual processor
>> machine would be faster.
>
> No. "SIOL" is only saying that at these CPU speeds nowadays, SIOL's
> hunger for raw speed is satisfied long ago and he is going after
> responsiveness rather than pure speed these days.
>
>> Without numbers means their reasoning is only speculation. This
>> machine happens to be a 486DX2-66. It has been more responsive
>> than many 200 Mhz Pentium machines. Explain that? After all
> that is how I *feel* - therefore it must be true!
>
> If it works that way under XP or Linux & XWindows & KDE 3.1.4 and
> lets you to hav job done without waiting for the machine, then
> certainly :o)
>
>> Lets say we are compiling for 2 to 5 minutes. One 300 Mhz
>> processor ends up with most of the load of a single thread
>> process. Now we press a key. Keypress is a high priority
>> task. In a dual processor system, one processor (either one)
>> must stop what it is doing and respond to that higher priority
>> task now. Either processor will take same time to perform
>> that response. Response takes longer (compared to a faster
>> single processor system) because each dual processor is
>> slower. But one higher speed CPU would execute same number of
>> instructions to stop compiling and respond to that higher
>> priority task. Which is going to respond to that high
>> priority task quicker? Faster processor in the single CPU
>> system. Slower processors in a dual system simply take longer
>> to respond to that interrupt.
>
> 1. Ever heard of CPU affinity ? When you start new tasks, kernel
> gets to decide what priority do new jobs get and whaich CPU gets
> to run them. It doesn't need to be a random choice.
>
> 2. With two or more CPU setup, one CPU can get all those keypresses
> under standard 18 ms interrupt while other hangs "do not disturb"
> sign and churns away at the max speed.
>
> 3. When you have many tasks and many of them demand real time
> reaction, CPU has to switch between tasks very frequently. Task
> switch costs microseconds. When frequency of task switches rises,
> considerable % of CPU power goes just for task switching. In 2.6
> kernel IIRC there is setting for preferred kernel clock for task
> switching. Higher clock means smoother multitasking, lower means
> smaller CPU overhead.
>
> For the bazilliont time, responsiveness is not strictly the same
> as speed. I don't really care about machines response to keypress
> time as ling it is under 100 ms or so. Same goes for mouse movement
> etc. There is some time allowed for the operation. If operation is
> done during this time, machine feels responsive, otherwise not.
> It doesn't have particular sense to strive for response anything
> faster than that, since user won't notice anyway, but it certainly
> should stay inside some time limits...
>
>> In a dual processor system, same number of instructions must
>> be processed (either in CPU doing the compiling or in other
>> more idle CPU). But since each CPU is slower, it takes longer
>> to respond to that human action - a keystroke. Single
>> processor system using faster processor will respond faster to
>> interrupt of that higher priority task.
>
> You don't seem to understand modern microprocessors. These are not
> the same as microcontrollers. One instruction on the microcontroller
> takes small, defined number of clocks. One instrustion on Athlon,
> P3, P4 etc can take anywhere from theoretical minimum number
> (usually one) to several hundred clock cycles, heavilly depending
> on circumstances.
>
> CPU speed is not nearly like water in a bucket- you can't just add
> and subtract it so easily. Problem with time of response is NOT CPU
> speed. If it had been, even 486 would be more than enough to have
> responsive system- just as you have observed before.
> Problem is that CPU can't always drop what it's doing just to react
> to your keypress or move a mouse pointer, open/close window etc.
> Sometimes it can't because it's executign a task that just has to be
> done right now (like preparing DMA transaction for CDR writing etc)
> and sometimes it can't response to many requests without crapping
> itself just with taskswitching.
>
> Dual CPU system can be much slower (in terms of absoulute speed-
> I'm not talking about responsiveness here) or it can be much faster
> (more than 2x ) than uniCPU system.
>
> UniCPU will be faster for tasks that are not multithreaded or tasks
> that are neatly multithreaded so that they can be executed in in
> linear order or at least in bigger chunks and cannot be executed in
> parallel. SInce thez tend to use latest geenration RAMs they will
> excell alsso with very memory intensive applications. Those are the
> situations where Duallies can't take advantage of extra CPU and
> where this CPU even slows them down (cache synchronisation-
> "snooping" etc)
>
> But in situations that demand parallel execution of many threads
> and tasks Duallie can be much faster, despite all. I fnumber of
> tasks is not too high and L2 of both CPUs is big enough not to
> get thrashed, dual CPU machine can beat single by more than 100%.
> Smaller taskswitch frequency will also bring its benefits.
>
>> Steve and SIOL cannot argue with any of this because it uses
>> the same type of speculative reasoning that they use. IOW the
>> only thing we can say for certain is that Steve and SIOL
>> *feel* their dual processor systems are faster - without doing
>> a double blind test - without any numbers - and without any
>> good solid facts to prove their claim.
>
> No, I "feel" my machine as more responsive. Not strictly "faster".
>
> Just as I said, I really couldn't care less if kernel compilation
> takes two or five minutes on my machine. Or how much Gentoo's
> "emerge -u world" takes- as long as it is inside some acceptable
> limits AND as long as I don-t see it.
>
> Do I really need to have numbers to see for example, that on my newest
> notebbok Toshiba Sattelite 5200-801 (2 GHz P4, 512 Mb DDR, GEforce 4
> Go etc) I can't watch a movie, listen to music or work under KDE
> smoothly when Gentoo does its updates ?
>
>> Junk science is used to claim, for example, that a dual 300
>> Mhz system will be more responsive compared to a single 600
>> Mhz system.
>
> But I'm not trying to be a scientist here. I was just talking about
> my experiences. I don't want to invest money into making science
> out of this. I had a Tualatin 1.3Ghz@1.7Ghz as the office machine
> that was meant for tasks from office work to CD burning, printing,
> besides that it serves as a firewall and router.
>
> Now the Tualatin board is in the drawer and on its place works Dual
> P3-1Gig. It works better. I can burn CDs on all three units and
> experience full bandwidth under samba or ADSL and even print and
> never ruin writing a single CD in the process.
>
> What instrumentation do I need to "prove this scientifically" ?
>
>> And since neither Steve nor SIOL have included other critical
>> information, then we really don't know about other essential
>> features that more affect overall system performance. For
>> all we know, the motherboard in that dual processor machine was
>> better designed than motherboard in a faster single processor
>> system.
>
> Motherboard differences can't bring or take that much from
> performance. But just to keep you happy, here it goes>
>
> Uni cpu was 1.3 GHz Tualatin, oveclocked from 100 MHz FSB to 133 MHz FSB.
> Board was QDI's 10T with VIA chiopset. It had 1.5 Gb SDRAM. I have used
> extra IDE card (Promise Ultra 100 Tx2) to connect four 180 Gb IDE disks
> (IIRC Maxtor). Graphic card is IIRC nVidia Geforce 4 MX400.
> And 3 TEACs CD-W540E units. There used to be four, but one has
> died recently Oh, yes, machine has had a couple of Ethernet cards
> in it (i think 3), since it also works as a firewall and router.
>
> When I changed it to duallie, I pretty much changed only board with
> CPUs. Everything else is the same. Even RAM.
> Dual system runs at native speed at 133 MHz FSB.
>
> <SNIP>
>> Above is posted a fundamental theory that says Steve and
>> SIOL are deceiving to us.
>
> Sure. And all that dual board sold are just a part of dirty plot
> to *** up the consumer.
>
>> However unlike their junk science reasoning, I will not claim
>> that the above theory proves they are wrong. I will simply say
>> that the above theory demonstrates their ideas can be flawed AND
>> that we need numbers.
>
> But you have numbers. Just look at the benchmarks.
> We are just saying that benchmarks don't cover the feeling of
> responsiveness.
> You have to experinece it for yourself, then decide.
> If your tasks don't need it, you won't understand why people are
> buying this stuff.
> If your tasks need it, you won't use single CPU machine ever again.
> You'll even start looking for dual CPU notebook...
>
>> I really don't care whether the dual processor system is
>> more responsive. I do care when junk science reasoning is
>> being promoted as a replacement for honesty - a claim based on
>> scientific principles - including numbers. They repeatedly
>> post a claim without numbers - or anything else to demonstrate
>> their claim. Lane Lewis is has quite correctly challenged
>> their 'facts' as only speculation based upon human perception.
>
> So, what should I do ? All I care is performance under load that I'm
> experiencing.
> I don't care for standard benchmarks. 3DMarks etc don't meen crap
> for the role this machine plays.
>
> Should I mount back the Tualatin with its board and roast a couple of
> hundred CD's under full load just to "scientifically proove a
> point" ? No, thanks.
>
> Why bother ? I'm not trying to sell you anything...

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