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I dont understand G flops... - Page 5

post #41 of 57
Quote:
Originally Posted by Alfwich View Post
Not ruining the test. There is no "SSS" grade at the end of a stress test; if the computer crashes you failed.

If your running a stress test program, and it crashes, regardless of the axillary programs running it is still unstable.
its ruining the test when you are doing several runs to look for stability. other programs take up cpu cycles so you cant tell if you are unstable by looking at flat gflops.
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post #42 of 57
Thread Starter 
is custom setting cheating.. I typed in 4 threads for quad core.. i have HT off.. and c1e and speedstep i couldnt find where to disable TURBO so... lol
    
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post #43 of 57
Thread Starter 
Quote:
Originally Posted by gsa700 View Post
I can confirm what you are saying about Gflops and vcore.

For example: at about 4.2 Ghz I get about 89 Gflops with my x6, but trying to lower the voltage to the minimum possible, to save on heat production, caused it to drop by 3-5 Gflops depending on voltage.

Upping the vcore too much will make linpack throw out an error but shows that Gflops are higher.

I try to split the difference and balance the heat against having no errors and then I have no problems with stability test and etc.

Hope that helps.

+1 REP!
wow that was an amazing answer i know im noob and ignorant but.. he picked up on my stuff :-P
    
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post #44 of 57
Thread Starter 
So... What would be the answer to loose or tight ram? If you have inconsistant G FLOPS or inconsistant time? is that considered "loose"?
    
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post #45 of 57
custom setting is not cheating, its the proper way to run the test.
also you have to close down all running programs, inc. antivirus, msn, steam etc.... before running test.

""Linpack uses 64 bit(double precision)floating point numbers to store the coefficient matrix etc.
It also uses SSE(2) instruction set & registers to run as fast as possible.Each SSE2 register is 128 bit wide,so we can pack 2 64 bit values in a single register.Current processors can perform a multiply-add operation on each 64 bit value in a single cycle.So it can do 2 multiplies+2 adds per cycle,which translates into 4 FLOP(floating point operations)per cycle.This is for one core.For a dualcore the value is 8 FLOP/cycle.With a quadcore it is 16.

Now let's calculate cpu performance in term of GIGAFLOPS for a few chips:

singlecore @ 2 GHz:2X4=8 GIGAFLOPS
Dualcore @ 3 GHz:3X8=24 GIGAFLOPS
quadcore @ 4 GHz:4X16=64 GIGAFLOPS
sixcore @ 4 GHz:4X24=96 GIGAFLOPS

Note that the above values are only the upper limits.The actual value we get in LinPack is somewhat lower due to the os overhead,LinPack bookkeeping & because Linpack cannot keep the CPU execution units busy all the time.


Calculating & estimating CPU performance in term of GIGAFLOPS

NOTE:From now on I use win64 with 4 gigs of ram in all the following discussion unless noted otherwise.

The gigflops value as reported by LinPack is roughly constant for a given CPU at a given core clock.The impact of ram speed & FSB is very small.
This is very important.It means we can have a fairly accurate estimate of the GIGAFLOPS we should achieve even before running the stress test.This is the index I have been talking about.
For example the index for E5200 @ 3 GHz is roughly 20 GIGAFLOPS.The ram speed & FSB could make this value change from 19 to 20.5;Hence if we run LinX/IBT and only get 15 GIGAFLOPS then we are obviously performing an improper test that is not very useful.I have seen people running an E5200 or E6300 @ 4+ GHz and only getting 13 GIGAFLOPS!!That's also why you sometimes see people getting ridculously low temps while running LinX/IBT.The temp differnce between a proper & improper run of the test could be more than 20 c°.

Furthermore,we only need one GIGAFLOPS estimate per chip.We can calculate other values by proportion.Let's say for an E8400 @ 3GHz the index is 21 GIGAFLOPS.Then for a 4GHz oc we can expect a performance value of 21X4/3=28.

But all these need to be verified.To this end,I performed a number of tests on my sig rig in vista64.First I overclocked my cpu to 3 GHz(333X9)with my ram clocked at 1066 mhz.After several runs of LinX(just to make sure) I found the GIGAFLOPS for this oc.Then I kept FSB & ram speed constant & raised the multi.In each step,I report the actual GIGAFLOPS as displayed by LinX and a value that I have calculated from the base(3GHz) oc.Here are the results:


CPU clock--------FSBXMulti---RAM Speed----Actual GIGAFLOPS---Calculated GIGAFLOPS
(GHz)--------------(MHz)
__________________________________________________ _________________
3.00--------------333X9.0---------1066--------------20.3-------------------- 20.3
3.16--------------333X9.5---------1066--------------21.2-------------------- 21.4
3.33--------------333X10----------1066--------------22.2-------------------- 22.6
3.50--------------333X10.5--------1066--------------23.1-------------------- 23.7
3.66--------------333X11----------1066--------------24.0-------------------- 24.8

As you see,the calculated & actual values are very close,which proves our point.
Also note that the calculated values are higher than actual values & the delta becomes more as we oc higher.The reason is we oc the cpu(and L1 & L2 caches),but keep the memory clock constant.To see if this is really the case I ran another test:

CPU clock-----FSBXMulti-----RAM Speed---------Actual GIGAFLOPS
(GHz)-----------(MHz)
_________________________________________________
3.00----------333X9.0----1066 with optimized settings-----20.3

3.00----------333X9.0----800 with stock settings-------------19.5


Once more our point is proven.In short,the impact of ram speed is small.The calculated value could roughly overestimate the actual value by 1%-3%.

Next let's try to make the calculated & actual GIGAFLOPS equal!This is done by overclocking CPU/FSB/RAM at the same time and by the same amount.The aim is to verify our assumption!

We start by setting CPU/FSB/RAM @ 2.5/200/800.Then we oc by 20% which is CPU/FSB/RAM @ 3/240/960.Finally we oc by 33% with CPU/FSB/RAM @ 3.33/266/1064


CPU clock--------FSBXMulti---RAM Speed----Actual GIGAFLOPS---Calculated GIGAFLOPS
(GHz)--------------(MHz)
__________________________________________________ _________________
2.50-------------200X12.5----------800--------------16.24-------------------- 16.24
3.00-------------240X12.5----------960--------------19.54-------------------- 19.49
3.33-------------266X12.5---------1064--------------21.71-------------------- 21.60

The results speak for themself.

Now let's guess the expected GIGAFLOPS for my CPU @ 4 GHz:20.3X4/3=27.06
But because I'm not overclocking my ram the actual value is a bit less.by consulting the first table I estimate the actual value to be 25.8 GIGAFLOPS.

We don't even need to find out our actual base GIGAFLOPS ourselves;We can ask others.Let's say you have an E8400.You ask other(reliable)people for an estimated(or measured) GIGAFLOPS for your chip @ stock.You are given a value of 21 GIGAFLOPS.Now you want to calculate the expected value for an oc of 3.6GHz.SO 21X3.6/3=25.2.Now a good estimate for your oc should be around 24.5 GIGAFLOPS.

The following is the estimated GIGAFLOPS for a few chips:

E5200 @ 3 GHz 19-20 GIGAFLOPS
E8400 @ 3 GHz 21-22 GIGAFLOPS
E9550 @ 4 GHz 54-56 GIGAFLOPS

I5 quadcore @ 4 GHz 59-61 GIGAFLOPS
I7 quadcore @ 4 GHz 60-62 GIGAFLOPS
Gulftown 6core @ 4 GHz 90-93 GIGAFLOPS"
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post #46 of 57
also looking around, the only time voltages affect gflops, is when the cpu is unstable.

"Voltage should have absolutely now effect on performance whatsoever so long as the CPU remains stable. If you're seeing a reduction in performance like this, the only thing that I can speculate is that you're making the QPI bus slightly unstable, and there is some kind of error correction that it can perform so that the whole system doesn't crash, but obviously error correction takes time, so you see a performance decrease.

On another note, you should never judge something off of a single test. There are large margins of error on most benchmarks. You should run at least 3-4 tests in order to see if there is actually a change. There are many things that run in the background of your computer that could cause the numbers reported to differ if the happened to take up some CPU cycles while the test was running"
http://forums.extremeoverclocking.co...d.php?t=338817
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post #47 of 57
Quote:
Originally Posted by L337Something View Post
LoL... yes i guess i am a noob but no need for your rude comments thats why we are all hear reading and learning... I understand WHAT IT IS i dont know why im getting lower G FLOPS with lower voltage... on same clock... so if I run my 4.0 ghz 175x 23.... at 1.268 volts ill get like 38 to 39 G FLOPS.... if i boost it to 1.33 or 1.35 i bet ill get like 58-61 i know i get in the upper 50s... but i know when i went 4.2 ghz at 1.4vcore i was getting 61-62 G FLOPS....
I didnt mean to offend you. I said you were "a bit of a noob", thats not harsh at all.
Also, you did ask what FLOPS were, which is why I told you.
If you knew what they were why did you ask?
post #48 of 57
Thread Starter 
all good i learned alot because of you and others appreciate it no hard feelings
    
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post #49 of 57
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now i just need to learn what the difference between "tight" ram timings or opposite... and how I can retrieve what my current timings are.
    
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post #50 of 57
Quote:
Originally Posted by L337Something View Post
now i just need to learn what the difference between "tight" ram timings or opposite... and how I can retrieve what my current timings are.
Download cpu-z click on the memory tab or check in bios

link
http://majorgeeks.com/CPU-Z_d425.html
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