i7 clock speed question

[ajaxxx]

ok so I have a huge dilema here. It's between these two processors.

i7 930 @2.8ghz
turbo boost to 3.06
bus speed @ 4.8GT/s

Or

i7 870 @2.93
turbo boost to 3.60
bus speed @ 2.5GT/s

the 870 has a way higher turbo boost looking very attractive, but the 930 has a much highers bus speed.
Which will be better for dolphin?

keep in mind that Overclocking will be out of the question because it will be an OEM pre-built computer from a manufacturer. I have a really hard time with lego's.... a computer would be a nightmare to build.

[lamedude]

LGA1156 (i870) brought the PCIe controller for video onto the CPU die. Its only 16 lanes so SLI/Xfire is limited to 8x speed. The DMI bus just has the handle the stuff coming of the PCH (southbridge) like SATA,USB,Ethernet, and the other PCI/PCIe slots. If the motherboard has a SATA3/USB3 controller connected to the PCH then you won't be able to get the full speed out of them. Some use the CPU PCIe lanes but that means no SLI/Xfire.
So the tl:dr is you want full speed SLI/Xfire,SATA3, or USB3 go 930.

[abfab126]

Sandy Bridge i5 and i7 are out Tomorrow , so just wait

[ajaxxx]

(01-09-2011, 07:56 PM)lamedude Wrote: LGA1156 (i870) brought the PCIe controller for video onto the CPU die. Its only 16 lanes so SLI/Xfire is limited to 8x speed. The DMI bus just has the handle the stuff coming of the PCH (southbridge) like SATA,USB,Ethernet, and the other PCI/PCIe slots. If the motherboard has a SATA3/USB3 controller connected to the PCH then you won't be able to get the full speed out of them. Some use the CPU PCIe lanes but that means no SLI/Xfire.
So the tl:dr is you want full speed SLI/Xfire,SATA3, or USB3 go 930.

thanks, I'll probably go with the 930

[NaturalViolence]

I don't know where you got those bus speeds from but both of those cpus use a QPI running at 4.8 GT/s. Only the dual core models have a QPI running at 2.4 GT/s. The difference between those two is that the 870 has a higher clock rate but lower memory bandwidth while the 930 has a lower core clock rate but a higher memory bandwidth.

870
2 memory channels x 1333 MHz each x 64 bits wide (width of each channel) / 8 (8 bits per byte) = 21.33 GB/s

930
3 memory channels x 1066 MHz each x 64 bits wide (width of each channel) / 8 (8 bits per byte) = 25.6 GB/s

(100 / 25.6) x 21.33 = 83.32%

So the 870 has 17% less memory bandwidth than the 930. Or another way to look at it is the 930 has 20.5% more memory bandwidth than the 870.

[Squall Leonhart]

don't waste your time with the 930, get the 950 instead, you can pick it up for LESS than a 930 in many places, and because of the higher multiplier you can hit 4Ghz at a lower base clock.

[ajaxxx]

(01-10-2011, 06:39 AM)NaturalViolence Wrote: I don't know where you got those bus speeds from but both of those cpus use a QPI running at 4.8 GT/s. Only the dual core models have a QPI running at 2.4 GT/s. The difference between those two is that the 870 has a higher clock rate but lower memory bandwidth while the 930 has a lower core clock rate but a higher memory bandwidth.

870
2 memory channels x 1333 MHz each x 64 bits wide (width of each channel) / 8 (8 bits per byte) = 21.33 GB/s

930
3 memory channels x 1066 MHz each x 64 bits wide (width of each channel) / 8 (8 bits per byte) = 25.6 GB/s

(100 / 25.6) x 21.33 = 83.32%

So the 870 has 17% less memory bandwidth than the 930. Or another way to look at it is the 930 has 20.5% more memory bandwidth than the 870.

i got the bus speeds from here-->
http://www.intel.com/products/processor/corei7/specifications.htm

I trust their Bus speed specifications are accurate since they make the damn things. But I understand where you are coming from since I know that the duo cores run on 2.5.
I guess the older I7's do too.

So in conclusion the higher bus speed the better right? even though it's clocked higher(taking bandwith into consideration)

[lamedude]

LGA1156 (i7 870) does not use QPI at all. Just that slow DMI bus. Since moving the memory controller on die bus speed makes no difference in CPU performance. Unless you need lots of bandwidth (RAIDing SSDs or 3x Xfire) it won't be a bottleneck. The triple channel memory also makes little difference in performance.

[Squall Leonhart]

Quote:Unless you need lots of bandwidth (RAIDing SSDs or 3x Xfire) it won't be a bottleneck. The triple channel memory also makes little difference in performance.

my copy to ram performance disagree's with you.

[Cyris]

you dont need an i7 core 99.9% of software and 100% of emulators are only optimized for dual core CPUs. i have a q6600 overclocked to 2.8ghz and when i monitor system performence windows , linux and mac only use the first 2 cores. unless your trying to run 5 emulators and 3 virtual versions of windows you wont get any better performence with your i7 core then i do with this q6600 if they're clocked at the same speed. what you need to do like the reply above me suggest is to get some triple channell DDR3 supported motherboard and get you a E8000 series core 2 dou or a QX9000 series quad core