What's the sweet spot for i7 Nehalem or even SB?

mikeny

November 20, 2011 11:58:12 PM

I have a i7-920 Nehalem that underclocks my ddr3-1600 RAM to 1066. Everyone says that it's Nehalem and no way around it. Do I chance it and try to bump it up to 1333? I have it in triple channel.....3x2GB and I wanted to double my RAM but this underclocking is and has annoyed me. Plus I was going to buy 2 6850's and crossfire them but don't want to hit a bottleneck possibly with the RAM.

Even though many have said no to this; this annoyance is really causing me to really consider moving to Sandy Bridge (and the Asus Gen3 mobo).

More about : sweet spot nehalem

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thebski

November 21, 2011 1:31:09 AM

Your memory speed is determined by 2 things: base clock (bclk) and memory multiplier. Base clock affects the whole system (CPU, QPI, DRAM, etc.) while the memory multiplier affects only memory. The standard on any Nehalem system is a multiplier of 8 with a base clock of 133. 8*133=1066 Mhz.

To reach 1600 Mhz, you can either change the multiplier from 8 to 12 (12*133=1596 Mhz) if you want to leave the rest of your system alone, or change the base clock to 200 (8*200=1600 Mhz) if you want to overclock your system, cpu and all.

Really, there's 3 ways. The multiplier moves in increments of 2.

8*200 bclk= 1600 mhz mem, 4000 mhz cpu
10*160 bclk= 1600 mhz mem, 3200 mhz cpu
12*133 bclk= 1600 mhz mem, 2660 mhz cpu

If you simply want the memory to run at rated speed then just change the multiplier to 12.

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mikeny

November 21, 2011 5:56:52 PM

thebski said:

Your memory speed is determined by 2 things: base clock (bclk) and memory multiplier. Base clock affects the whole system (CPU, QPI, DRAM, etc.) while the memory multiplier affects only memory. The standard on any Nehalem system is a multiplier of 8 with a base clock of 133. 8*133=1066 Mhz.

To reach 1600 Mhz, you can either change the multiplier from 8 to 12 (12*133=1596 Mhz) if you want to leave the rest of your system alone, or change the base clock to 200 (8*200=1600 Mhz) if you want to overclock your system, cpu and all.

Really, there's 3 ways. The multiplier moves in increments of 2.

8*200 bclk= 1600 mhz mem, 4000 mhz cpu
10*160 bclk= 1600 mhz mem, 3200 mhz cpu
12*133 bclk= 1600 mhz mem, 2660 mhz cpu

If you simply want the memory to run at rated speed then just change the multiplier to 12.

So just change the memory muliplier to 12? Then save and quit? Change nothing else?

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thebski

November 23, 2011 3:43:18 PM

That should do it for you.

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jaquith

Memory Master

November 23, 2011 4:09:50 PM

It depends on what MOBO you have, and the 'simplest' way is to set RAM using XMP if it's a single set and it offers XMP (most all do).

ASUS: AI Overclock Tuner -> XMP, and eXtreme Memory Profile -> High Performance
Gigabyte: Extreme Memory Profile (X.M.P.) -> Profile1

The use of XMP will set the proper Frequency, CAS Timings and Voltage for your RAM. Otherwise you can set everything manually; in that case I need to know the exact MOBO and RAM.

For both the LGA 1366 and LGA 1155 SB DDR3-1600 is the ideal RAM Frequency for gaming. The LGA 1366 when combined with a >160MHz BCLK the faster DDR3-1800~DDR3-2000 shows an improvement whereas the LGA 1155 has no measurable gains.

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