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CPU and memory pairing for i5 2500k?

M

mike_6289

Limp Gawd
Joined
Dec 31, 2004
Messages
316
First off I'll start by saying that my knowledge of computer hardware is sort of outdated, but I've been trying to do some catching up lately as I'm building a new system.

My understanding is:
- 3 channel RAM is for 6 core processors
- 2 channel RAM is for 2 or 4 core processors

- 6 core processors have a maximum memory bandwidth of 25.6 (or something gB/s)
- 4 core processors have a maximum memory bandwidth of 21.3 (or so gB/s)

- 3 channel at DDR1066 saturates the FSB (or whatever it's called now)
- 2 channel at DDR1333 "

Am I correct?
If I am, is there any point in having RAM faster than 1333 with an i5 2500k?
If I'm not, could you explain where I'm wrong?
 
flegg said:
no k chipsets have 3 chan
Click to expand...

what about the memory bandwidth part?
is there any use of having RAM faster than the interface with the processor?

edit: pretty sure you're wrong.
anyone else?
 
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Quote from Intel site on i5 memory controller
INTEGRATED DDR3 MEMORY CONTROLLER
Integrated memory controller enables two channels of DDR3 1333 MHz memory, resulting in up to 21 GB/sec memory bandwidth. Plus the memory controller's lower latency and higher memory bandwidth delivers amazing performance for data-intensive applications

Quote from Intel site on older i7 memory controller
INTEGRATED DDR3 MEMORY CONTROLLER
With the integrated DDR3 memory controller, the Intel Core i7 enables three channels of DDR3 1066 MHz memory, resulting in up to 25.6 GB/sec memory bandwidth. Plus the memory controller's lower latency and higher memory bandwidth delivers amazing performance for data-intensive applications.

So yes none of the K's are 3 channel to date. and the limit is the built on memory controller not the motherboard. So that means all LGA 1155 sockets will be using only 2 channels.

http://www.intel.com/consumer/products/processors/compare-processors.htm?select=desktop
 
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Jhadur said:
Quote from Intel site on i5 memory controller
INTEGRATED DDR3 MEMORY CONTROLLER
Integrated memory controller enables two channels of DDR3 1333 MHz memory, resulting in up to 21 GB/sec memory bandwidth. Plus the memory controller's lower latency and higher memory bandwidth delivers amazing performance for data-intensive applications

Quote from Intel site on older i7 memory controller
INTEGRATED DDR3 MEMORY CONTROLLER
With the integrated DDR3 memory controller, the Intel Core i7 enables three channels of DDR3 1066 MHz memory, resulting in up to 25.6 GB/sec memory bandwidth. Plus the memory controller's lower latency and higher memory bandwidth delivers amazing performance for data-intensive applications.

So yes none of the K's are 3 channel to date. and the limit is the built on memory controller not the motherboard. So that means all LGA 1155 sockets will be using only 2 channels.

http://www.intel.com/consumer/products/processors/compare-processors.htm?select=desktop
Click to expand...

Since the FSB can't be changed anymore, there's no way to increase the maximum memory bandwidth capability of processors, right? So what is the reason for all these boards saying DDR3 1600 and higher? Ivy Bridge?
 
mike_6289 said:
Since the FSB can't be changed anymore, there's no way to increase the maximum memory bandwidth capability of processors, right? So what is the reason for all these boards saying DDR3 1600 and higher? Ivy Bridge?
Click to expand...

There is no "FSB" in the traditional sense on Sandy Bridge. The memory controller is embedded on the same die as the CPU/GPU, and there is a VERY fast local bus connecting the three. Since the vast majority of bandwidth is used by these two devices directly, there's no danger of being constricted by the bus connecting the processor to the outside world.

The memory controller on Sandy Bridge has been tweaked to astonishing levels: you can actually get 20GB/s real-world out of DDR3 1333, and performance is about %10 better than Nahalem . It also scales up to DDR3 2133 30GB/s.

Sandy Bridge can run some very fast memory sticks.

But the performance benefit is minimal because bandwidth is already plentiful at stock 1333

The extra memory bandwidth is mostly just marketing fluff for four cores, but you might see a benefit from DDR3 1600 if you overclock. Don't waste your money on extremely expensive 1866+ chips.
 
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Right now none of the 2nd generation Intel® Core™ processors are using triple channel memory. Of all the unlocked CPUs designated with a “K” none of them use triple channel memory. The only processors that we have released that use triple channel memory are the 1st generation Intel Core i7-9XX, the Intel Core i7-9XX Extreme Edition, the Intel Xeon® W35XX, the Intel Xeon 55XX and Intel Xeon 56XX.

Overall while going from dual channel to triple channel the performance gain is not as great as going from the 1st generation to the 2nd geneation Intel Core processors.
 
For sandy bridge setup is simple:
1.6v or lower
dual channel kit

But there's people using 1.65v without a problem


Some days ago i bought for my sandy setup, g skill 2133mhz 4gb 1.6v... and they run flawlessly
 
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