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Should i send my CPU back to overclockers I7 High L3 Cache Latency

ViRuS2k

ViRuS2k

ViRuS2k

Soldato
Joined
26 Jan 2004
Posts
6,293
Location
Scotland
I have tryed everything but i cant seem to get the L3 latency down.
i dont know whats causeing it becuse it use to be perfect at 4ns but now its in the 20s

do i have a defective cpu.

I even sent my reapers back and bought some Ocz 2000mhz blades.
and it gives the same as what the reapers did. no l3 latency change...

also does anyone know what the default advanced timeings are for this 2000 stuff.
cause i wanna know the fastest timeings to use for

1600 speeds and 1800 aswell as 2000 as i want to make up a few profiles.
to find out what is the best but i cant find the default timeings other than 9.9.9.30 but i want to know what the others are.

here is a picture showing you the high L3 latency, i have never seen this before on other peoples screenshots.

4200ghzi7htenabled.jpg
 
first off ide clear the bios completely & start from scratch, just to be sure there is some kinda cpu problem and not a bios inflicted snafu some how?.

L3-latency.jpg
 
Im going to send the cpu back.
I cant for the life of me figure it out..


My settings are :

Biostar, Latest bios. Cpu tweak one.

cpu 0100+ 1.31v in windows
cpu pll auto 1.8 Actual
cpu vtt 1.35v in windows
Dram 1.65v = 1.66v in windows
NB/SB / Auto
Qpi/Pci-e 1.200v
Uncore 3600mhz
Qpi 3600mhz
Multi 21x
200x bclk


Did a full memtest loop, no errors on memory.

I dont understand becuse i cant reproduce what it use to be.
here is a screenshot that i did at a slower setting and the L3 cache latency is normal.

Benchmarking_Testing.jpg


also look at the diffrence in speed on the L3 cache line aswell as the memory read write and copy speeds.

i have no idea what the freakin hell is going on and its starting to really tik me off,

where the hell are all the experts when you need em.
 
im no expert, but i may have an inkling of whats going on

the L3 cache is the highest level of cache meaning that this is the first port of call for data entering the cpu, but the speed at which this data can enter is going to be limited to the speed of the QPI. Seen as you have such a high overclock my guess would be that the CPU is too fast for the data on the QPI, causing "lag" as the data queues to enter, so to speak

so id suggest retruning it to stock and checking the L3 latency, and then perhaps just trying to up your QPI speed and see if that helps

this is a bit of a stab in the dark from me though to be honest, im probably completely wrong and dont even own an i7 but i just remember seeing something similar before, hope it helps
 
ViRuS2k said:
Should i send my CPU back to overclockers
Click to expand...
I don't think that is worthy of an RMA do you! :o

I fancy boys said:
the L3 cache is the highest level of cache meaning that this is the first port of call for data entering the cpu
Click to expand...

I always thought Level 1 cache was the fastest, then Level 2 the next fastest leaving level 3 cache as the slowest and furthest away! :D
 
Last edited:
Hmmm, i will try your theory later fancy boys cheers for the help
and mattus no its not hindering my systems performance.

its this one benchmark that puzzleing me LOL so im trying to figure out why the latency is so high...


hmmm, could it be becuse of this : Qpi/Pci-e 1.200v
should i give it more volts ? and whats the maximum Qpi-Pci-e should go as i dont want to fry the cpus memory controller.
 
Either the software is wrong or it's something to do with the QPI speed, with the big latency, your QPI is only 360MHz, small latency it's 3600MHz.
 
Jokester said:
Either the software is wrong or it's something to do with the QPI speed, with the big latency, your QPI is only 360MHz, small latency it's 3600MHz.
Click to expand...

Not sure im getting what you mean.

? got any suggestions what to change to get the latency small again. cause it use to be small LOL then it jumped for some reason.

I dont think its a defective cpu so im not going to rma it but this is strange.
 
Your latency is an order of magnitude bigger when your QPI frequency is an order of magnitude smaller.

I wouldn't be surprised if the L3 cache is running at the QPI frequency hence why it's so slow when your QPI frequency is so low.
 
gettingthere.jpg


ok getting somewhere now.

Upped the QPI/PCIe voltage from 1.200v to 1.250v

and what has happened is the l3 cache speeds have all come back :)
latency is still there though i think i might need some more QPi voltage
copy speeds in memory have improved aswell.

does anyone know if im undervolting the QPI and thats causeing it cause im not sure how high im ment to take this voltage setting.

anyone know ?
 
well i'm running QPI around the 1.3 mark, but i'm still at that fiddling stage while i settle on a 24/7 clock. having said that, pretty much every guide/thread ive seen have said to keep it in the range of 1.2 - 1.35 for max stability. so you could be erring on the low side for your particular chip.
 
hmmmm

Ok how about someone just tell me the settings to use for 4.2ghz
memory will be at 1600mhz
all voltages are already set
21x200

whats the rest i need to know so i get the uncore and Qpi correct ? im sick of fiddleing LOL
 
ViRuS2k said:
Ok how about someone just tell me the settings to use for 4.2ghz
Click to expand...
Hey ViRuS2k,

Not that many people have Core i7 yet and the people that do still are working it out!

You really should be pushing on with your own experimentation, bit of trial and error and all of that!

If you get a bit worried and afraid of melting your new shiny then a few cans of beer helps! :p

Dutch Courage I think its called! :o
 
rjkoneill said:
i really think the testing department would 'no fault found' it in all honesty
Click to expand...
Is there any chance of a bribe or some other shady deal for the chip to be found faulty! :p

Little brown envelope stuffed with a stack of crisp £5 notes huh! :eek:

Little deposit in an off-shore account (or paypal etc) :D
 
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